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NATURE-BASED SOLUTIONS FOR DISASTER RISK MANAGEMENT

Coastal Flooding and Erosion Protection

Photo credit: flickr/ Northshore school of art

This presentation describes a set of Nature-based Solutions (NBS) that can protect, restore, and manage coastal ecosystems to safeguard communities, and to enhance development project performance. It also discusses the challenges and limitations of these solutions.

This slide deck is part of a suite of information and training materials prepared for the World Bank on NBS. These resources are designed for the World Bank and its network to understand how NBS can enhance their project portfolio, and how to consider and utilize these solutions. These resources include:

A flagship report “Integrating Green and Gray: Creating Next-Generation Infrastructure” (Browder et al. forthcoming 2019): Featuring guidance to evaluate and design NBS, with more than a dozen NBS case studies
A booklet about key considerations for using NBS for DRM
A factsheet about the World Bank NBS program
A series of PowerPoints featuring NBS for DRM objectives, including an overview, coastal flood risk management, river flood risk management, and urban flood risk management.

For more information and resources, visit https://naturebasedsolutions.org/.

References:

World Bank. 2018. “Natural Hazards - Nature-Based Solutions.” Project Platform. Natural Hazards - Nature-Based Solutions. https://naturebasedsolutions.org/.

Image source: https://en.wikipedia.org/wiki/Coral_reef_protection#/media/File:Coral_Outcrop_Flynn_Reef.jpg

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MANY TERMS FOR “NATURE-BASED SOLUTIONS”

Source: Cohen-Shacham et al. 2016; UNEP et al. 2014; EC 2015;

Lo 2016; WWF 2017; USACE n.d.; EcoShape 2018; WBCSD 2017

“Nature-based solutions” (NBS) are strategies that can protect, sustainably manage and restore natural and modified ecosystems. They harness natural processes and ecosystem services for functional purposes, such as managing the impacts of natural hazards and climate change impacts. NBS can address pressing societal challenges and risks effectively and adaptively.

What we call “NBS” is synonymous with a number of other terms used in common practice to describe the same or similar measures, listed on the screen. These include:

Implementing nature-based flood protection (WB 2017)
Engineering with nature (USACE n.d.)
Building with nature (EcoShape 2018)
Green Infrastructure (UNEP et al. 2014)
Nature-based flood management (WWF 2017)
Ecosystem-based adaptation to climate change (Lo 2016)
Natural infrastructure (WBCSD 2017)
Living Shorelines (NOAA 2017)

While DRM and development objectives conventionally involve built engineering measures, the application of NBS have increasingly emerged as viable alternatives or complements to traditional approaches.

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References:

Cohen-Shacham, E., G. Walters, C. Janzen, and S. Maginnis, eds. 2016. Nature-Based Solutions to Address Global Societal Challenges. IUCN International Union for Conservation of Nature. doi:10.2305/IUCN.CH.2016.13.en.
UNEP, IUCN, TNC, WRI, and U.S. Army Corps of Engineers. 2014. Green Infrastructure Guide for Water Management: Ecosystem-Based Management Approaches for Water-Related Infrastructure Projects. http://www.unepdhi.org/-/media/microsite_unepdhi/publications/documents/unep/web-unep-dhigroup-green-infrastructure-guide-en-20140814.pdf.
European Commission, and Directorate-General for Research and Innovation. 2015. Towards an EU Research and Innovation Policy Agenda for Nature-Based Solutions & Re-Naturing Cities: Final Report of the Horizon 2020 Expert Group on ’Nature-Based Solutions and Re-Naturing Cities’ : (Full Version). Luxembourg: Publications Office of the European Union. http://dx.publications.europa.eu/10.2777/765301.
Lo, V. 2016. “Synthesis Report on Experiences with Ecosystem-Based Approaches to Climate Change Adaptation and Disaster Risk Reduction.” Technical Series, no. 85.
WWF. 2017. Natural and Nature-Based Flood Management: A Green Guide. WWF. https://c402277.ssl.cf1.rackcdn.com/publications/1058/files/original/WWF_Flood_Green_Guide_FINAL.pdf?1495628174.
US Army Corps of Engineers. n.d. “Engineering with Nature.” https://ewn.el.erdc.dren.mil/.
Ecoshape. 2018. “Building with Nature.” Building with Nature. https://www.ecoshape.org/en/.
WBCSD. 2017. “Incentives for Natural Infrastructure Review of Existing Policies, Incentives and Barriers Related to Permitting, Finance and Insurance of Natural Infrastructure.” WBCSD. https://www.wbcsd.org/Clusters/Water/Natural-Infrastructure-for-Business/Resources/Incentives-for-Natural-Infrastructure.
NOAA, and US Department of Commerce. 2017. “What Is a Living Shoreline?” https://oceanservice.noaa.gov/facts/living-shoreline.html.
World Bank. 2017. Implementing Nature-Based Flood Protection: Principles and Implementation Guidance. Washington, D.C: World Bank Publications. doi:10.1596/978-1-4648-0484-7

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COASTAL REGIONS

Photo credit: Flickr/Anh Dinh; Source: Kummu et al. 2016

Represent 9% of global land area
House 28% of the global population (1.9 billion people)
Produce 42% of global GDP

Coastal areas have been critical for human livelihoods, development and trade throughout our history. These regions, although small in total land mass, are vastly important to local and global economies. These regions are small but mighty. Although coastal low-lands (or the near-coast zone, which is classified as <100km from the coastline and <100m elevation), represent only 9% of global land surface area, in 2010 they were home to 1.5-1.9 billion people, or 28% of the total global population, and produced 42% of global GDP.

Since the 1900s, half the global population has lived within 200km of the coast. The number of people in these areas has increased tremendously – by 1 billion since 1990.

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References:

Kummu, Matti, Hans de Moel, Gianluigi Salvucci, Daniel Viviroli, Philip J Ward, and Olli Varis. 2016. “Over the Hills and Further Away from Coast: Global Geospatial Patterns of Human and Environment over the 20th–21st Centuries.” Environmental Research Letters 11 (3): 034010. doi:10.1088/1748-9326/11/3/034010.
United Nations, and Department of Economic and Social Affairs. 2014. World Urbanization Prospects, the 2014 Revision Highlights. New York: United Nations. https://esa.un.org/unpd/wup/publications/files/wup2014-highlights.pdf.
Image: https://bit.ly/2SAeYNd

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More than half of all megacities are located in coastal areas

URBANIZATION: 2018

Source: The Economist 2015

54% of the global population lives in urban areas. It’s no coincidence that many of these growing population and economic centers are located in coastal areas.
Urbanization in the near-coast zone increased from 25% in 1900 to 63% by 2010. Today, more than half of all megacities with populations of 10 million people or more are located on the coast, and the population in this region will only continue to grow.

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References:

United Nations, and Department of Economic and Social Affairs. 2014. World Urbanization Prospects, the 2014 Revision Highlights. New York: United Nations. https://esa.un.org/unpd/wup/publications/files/wup2014-highlights.pdf.
The Economist. 2015. “Bright Lights, Big Cities,” February 4. https://www.economist.com/node/21642053?fsrc=scn/tw_ec/bright_lights_big_cities.
Kummu, Matti, Hans de Moel, Gianluigi Salvucci, Daniel Viviroli, Philip J Ward, and Olli Varis. 2016. “Over the Hills and Further Away from Coast: Global Geospatial Patterns of Human and Environment over the 20th–21st Centuries.” Environmental Research Letters 11 (3): 034010. doi:10.1088/1748-9326/11/3/034010.

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Source: The Economist 2015

More than half of all megacities are located in coastal areas

URBANIZATION: 2030

By 2030, the global urban population is projected to increase by another 1 billion people. By 2050, the near-coast zone is expected to house 26% of the global population, or 2.4 billion people. 80% of these coastal-dwellers will live in cities.
Unfortunately, the growth in population and urbanization in coastal regions has added immense pressure to coastal resources, contributing to the environmental decline of coastal ecosystems. And coastal low-lands are becoming particularly sensitive to sea level rise and intensified storms as the climate changes.

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References:

The Economist. 2015. “Bright Lights, Big Cities,” February 4. https://www.economist.com/node/21642053?fsrc=scn/tw_ec/bright_lights_big_cities.
Kummu, Matti, Hans de Moel, Gianluigi Salvucci, Daniel Viviroli, Philip J Ward, and Olli Varis. 2016. “Over the Hills and Further Away from Coast: Global Geospatial Patterns of Human and Environment over the 20th–21st Centuries.” Environmental Research Letters 11 (3): 034010. doi:10.1088/1748-9326/11/3/034010.
Creel, Liz. 2003. Ripple Effects: Population and Coastal Regions. Washington, D.C: Population Reference Bureau. https://www.phttps://www.prb.org/rippleeffectspopulationandcoastalregions/rb.org/wp-content/uploads/2003/09/RippleEffects_Eng.pdf.

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FLOODING AND EROSION ARE TWO IMPORTANT HAZARDS FACING COASTAL COMMUNITIES

Photo credit: Flickr/Mohamed Malik

Contributing factors:

Development decisions
Ecosystem degradation
Sea level rise
Changing weather patterns
Natural disasters

Flooding and erosion are two top hazards facing coastal areas. These hazards – which threaten both built and natural landscapes – are on the rise due to a combination of factors, including:

Humans inhabiting risky areas, degrading landscapes and ecosystems;
Sea level rise;
Changing weather patterns and a changing climate;
Natural disasters that bring intense wind, rainfall or storm surge.

Coastal communities are increasingly exposed to flood risks and erosion as:

Ecosystems become altered by human encroachment and land is claimed along the coast and hinterland for development and settlements.
Wind tides, coastal storms and surges create abnormal rise in seawater, ultimately submerging the coast and hinterland in floodwater. And, as surface areas are permanently inundated by rising sea levels.
Sediment stocks like sand and rock are removed from the beach system and deposited elsewhere by changing wave, current and wind patterns, and storm surge, compromising dune integrity and protection of the hinterland.

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References:

UNEP, IUCN, TNC, WRI, and U.S. Army Corps of Engineers. 2014. Green Infrastructure Guide for Water Management: Ecosystem-Based Management Approaches for Water-Related Infrastructure Projects. http://www.unepdhi.org/-/media/microsite_unepdhi/publications/documents/unep/web-unep-dhigroup-green-infrastructure-guide-en-20140814.pdf.
USGS. 2017. “National Assessment of Storm-Induced Coastal Change Hazards.” National Assessment of Storm-Induced Coastal Change Hazards. https://coastal.er.usgs.gov/hurricanes/.
Creel, Liz. 2003. Ripple Effects: Population and Coastal Regions. Washington, D.C: Population Reference Bureau. https://www.phttps://www.prb.org/rippleeffectspopulationandcoastalregions/rb.org/wp-content/uploads/2003/09/RippleEffects_Eng.pdf.
Image source: Flooding in Chennai, India: https://www.flickr.com/photos/malikdhadha/23131532782/in/photolist-Bf49NJ-612fP-612eP-5UXGz8-5V3fGy-5V3gY5-5UXQMi-5V37PW-QvqX5h-BeaAmi-5V32x7-BGXPP8-BEkVZQ-BPW3EK-5V35gy-5V39Jq-ENZ2Cm-5UXP5K-BEoRmK-QvqWcL-jQPDU-5UXE3e-RMUPPg-5V3brY-BkxHTy-CdiTPy-ENZV1m-ENZUoj-CudyHW-CWkAXk-CnQg46-CLMBnJ-MErENA-MErCZ5-MErDR5-MErEFm-MErEs5-MErE9u-MErEkb-MErD6C-CLMzMj-CnQeAr-CWkzfH-CLMzNw-CP3siP-CP3sdt-CP3sdZ-CP3w4e-BYPKoN-CLMDuj

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COSTLY CONSEQUENCES

Source: Hallegatte et al. 2013; NOAA 2016

Photo credit: Flickr/ Oregon Sea Grant

US$6 billion per year lost globally from flooding in major coastal cities

In the US alone, erosion affects more than 40% of coastlines, resulting in ~US$500 million/yr in coastal property losses

The consequences of coastal flooding and erosion can be incredibly costly, and can even threaten human lives.
In 2005, average losses from flooding of the 136 largest coastal cities in the world amounted to around US$6 billion per year. By 2050, this is expected to increase to at least US$52 billion per year, but could be as high as US$1 trillion or more per year due to the impacts from climate change and land subsidence.
9 of the 10 most vulnerable cities to flooding are in developing countries, which may struggle to bounce back from these costly events (vulnerability measured in terms of percentage average annual losses of city GDP) :

Guangzhou, China
New Orleans, USA
Guayaquil, Ecuador
Ho Chi Minh City, Vietnam
Abidjan, Côte d'Ivoire
Zhanjiang, China
Mumbai, India
Khulna, Bangladesh
Palembang, Indonesia
Shenzhen, China

Flooding example: In 2011, a magnitude 9.0 earthquake off the coast of Sendai, Japan caused a massive tsunami with waves nearly 40-meters high that swept more than 10 kilometers inland along the coast, collapsing 190 kilometers of dikes and killing nearly 18,000 people. Over 1 million buildings were destroyed in full or in part, and total economic costs were estimated to reach US$210 billion from this single event.
Erosion damages are difficult to quantify globally, and official estimates on erosion in World Bank client countries do not presently exist. However, in the US alone more than 40% of coastlines are affected by erosion, resulting in an excess of $500 million in coastal property losses annually, including damage to structures and loss of land.

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References:

NOAA. 2016. “Coastal Erosion.” U.S. Climate Resilience Toolkit. Coastal Erosion. https://toolkit.climate.gov/topics/coastal-flood-risk/coastal-erosion.
Hallegatte, Stephane, Colin Green, Robert J. Nicholls, and Jan Corfee-Morlot. 2013. “Future Flood Losses in Major Coastal Cities.” Nature Climate Change 3 (9): 802–806. doi:10.1038/nclimate1979.
World Bank. 2012. Learning from Megadisasters: Lessons from the Great East Japan Earthquake. Learning from Megadisasters: Lessons from the Great East Japan Earthquake. Washington, D.C: World Bank Publications. https://openknowledge.worldbank.org/bitstream/handle/10986/17107/793520WP0JP0Ea00PUBLIC00Box0377373B.pdf?sequence=1&isAllowed=y.
Image: Erosion in Oregon, USA: https://www.flickr.com/photos/oregonseagrant/6036438502/in/photolist-acqjRU-2MESm4-8d53rY-7sNuEp-nDgHVS-Uio278-pWcG5q-7VgwaZ-jsHpAR-nCMZg5-4P8vBv-6Gry3s-nv5wpS-24c7rqW-dp7kNf-oXXsLz-UDU28L-dp7eZc-d3ys3u-g7JaSw-dfsSXp-p2AN7r-b37pnR-h5J9YG-6PLG6F-kY3GaG-jPv5HX-p2AQ6M-9KodZV-7vTBJ4-b2eWUZ-acqjT3-66ZuVV-dp7dzV-dp7dQX-oz15p5-h4bfhs-Fkggwu-EA3Ae-FGkHt9-srtReR-dp7bQR-53RpJL-9FoC3a-hbSCzb-bPPDgt-23QRo7b-gVNrX6-7AVYUS-6599oH

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WORLD BANK INVESTMENT PORTFOLIO: � DISASTER RISK MANAGEMENT (DRM)

Source: GFDRR internal data analysis 2018

Invested

~US$49 billion (FY2012-2017) in more than 600 DRM projects globally

61 projects have targeted coastal flooding with around US$3.78 billion committed

123 projects have targeted coastal erosion with US$20.4 billion in committed

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COASTAL RISK REDUCTION MEASURES INCLUDE NBS

Source: USACE 2013; Spalding et al. 2014

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STRUCTURAL STRATEGIES

Source: World Bank 2017

	Nature-based Solutions (NBS)
Built	Hybrid	Natural
Hard, gray, engineered structures built to address development objectives	Combination of ecosystem elements and hard engineering interventions for addressing development objectives	Creation, protection or restoration of only ecosystem elements for addressing development objectives

This slide presents a typology of the structural infrastructure strategies included in coastal DRM projects, including built infrastructure and NBS—both green and hybrid.
While built infrastructure is conventional gray or hard engineered infrastructure solutions, NBS can be classified as completely ‘green’ (i.e., ecosystem elements only) or ‘hybrid’ (i.e., combination of ecosystem elements and built infrastructure), and are used as alternatives or complements to traditional gray infrastructure approaches.
NBS protect, sustainably manage and restore natural and modified ecosystems that address societal challenges, like flooding and erosion, effectively and adaptively while simultaneously providing human well-being and biodiversity benefits.

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References:

World Bank. 2017. Implementing Nature-Based Flood Protection: Principles and Implementation Guidance. Washington, D.C: World Bank Publications. doi:10.1596/978-1-4648-0484-7.

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CONVENTIONAL: ‘BUILT’ INFRASTRUCTURE

Photo credit: Flickr/Ecks Ecks

Coastal solutions include:

Offshore breakwaters
Dikes
Seawalls
Groins
Concrete or rock embankments

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NBS: ‘NATURAL’ INFRASTRUCTURE

Photo credit: Flickr/Ed Hunsinger

Ecosystems include:

Mangroves
Coral reefs
Oyster beds and reefs
Seagrasses
Sandy beaches and dunes
Coastal marshlands and other wetlands

NBS and their ecosystem services can be used to protect against storms, rising tides and floods, buffering storm surges and slowing coastal erosion.
Nature-based solutions for coastal areas include regenerating, protecting or creating ecosystems such as:

Mangrove forests
Seagrass or oyster beds
Oyster reefs
Sandy beach and dunes
Coastal marshlands and other wetlands
Coral reefs

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References:

TNC. 2016. “Natural Solutions | Coastal Resilience.” http://coastalresilience.org/natural-solutions/.
Cohen-Shacham, E., G. Walters, C. Janzen, and S. Maginnis, eds. 2016. Nature-Based Solutions to Address Global Societal Challenges. IUCN International Union for Conservation of Nature. doi:10.2305/IUCN.CH.2016.13.en.
UNEP, IUCN, TNC, WRI, and U.S. Army Corps of Engineers. 2014. Green Infrastructure Guide for Water Management: Ecosystem-Based Management Approaches for Water-Related Infrastructure Projects. http://www.unepdhi.org/-/media/microsite_unepdhi/publications/documents/unep/web-unep-dhigroup-green-infrastructure-guide-en-20140814.pdf.
Sutton-Grier, A.E., K. Wowk, and H. Bamford. 2015. “Future of Our Coasts: The Potential for Natural and Hybrid Infrastructure to Enhance the Resilience of Our Coastal Communities, Economies and Ecosystems.” Environmental Science & Policy 51: 137–148
Image: https://www.flickr.com/photos/edrabbit/8245946357/in/photolist-sXHdyx-dyLtnu-7Trg6L-WTSp8Z-XSg2H1-5bTYy-7BUKkP-eibGcD-KPPk2-cSgsX5-pkFP5-77BUtW-5r8FE4-3d4wwJ-67i8x6-xp6Ma-3edjqf-bKxtt-2EBX1D-25tYFT-cwyrz-7MhBg-h8KoZV-5tRR3G-2Eyouc-23fxPXG-c4r5NJ-6k19j3-gUogJz-adGmzW-KPRMv-4LbcDh-geA9jc-9WQFms-76YNd9-7Z5Ncx-6NooYZ-dyECyV-7DjZJY-e23Sz-6Lc1G7-2ED4yE-dyEXpn-bdtDY6-25yer3-bduTyr-obA62E-6m8qMk-dyLaXQ-5A3TNn

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‘HYBRID’ INFRASTRUCTURE

Sources: World Bank 2016; Spalding et al. 2014

Hybrid setup of mangroves and dikes can reduce necessary dike height and costs

‘Hybrid’ NBS offer a complementary approach that feature a combination of ecosystem elements and built infrastructure. For example, inshore submerged breakwaters can be installed behind coral reef to be restored.

Other examples include mangrove planting in front (e.g., seaward) of dike, for dike longevity; removable sea walls seaward of growing mangroves as temporary shelter for mangroves and coast; or offshore breakwaters as basis for coral transplants.

Advantages of hybrid measures include the ability to:

Reduce spatial requirement as compared to natural solutions.
Reduce time lag between creation of DRM solution and its effectiveness, (for example, with a temporary sea wall can protect growing mangroves while also protecting the shore until the mangroves take over this function).
Decrease maintenance cost and increase longevity of gray infrastructure solutions by, for example, decreasing wave impact on gray solutions over time.
Increase the public perception of security as compared to solely using an NBS.

These measures have the potential to bring in new co-financing from funders with non-DRM missions such as conservation trust funds like the Adaptation Fund, Global Environmental Facility, and others.

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References:

Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
Sutton-Grier, A.E., K. Wowk, and H. Bamford. 2015. “Future of Our Coasts: The Potential for Natural and Hybrid Infrastructure to Enhance the Resilience of Our Coastal Communities, Economies and Ecosystems.” Environmental Science & Policy 51: 137–148.
Jongman, Brenden, Hessel C. Winsemius, Stuart A. Fraser, Sanne Muis, and Philip J. Ward. 2018. “Assessment and Adaptation to Climate Change-Related Flood Risks.” Oxford Research Encyclopedia of Natural Hazard Science, February. doi:10.1093/acrefore/9780199389407.013.278.
World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.

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ADVANTAGES OF NATURE-BASED SOLUTIONS

Photo credit: Flickr/Synecdoche

Can be more cost-effective
Able to adapt and regenerate
Provide wide range of additional co-benefits beyond flooding and erosion protection

NBS may also be more cost-effective in some cases. They can present lower construction and maintenance costs than built solutions, and have the capacity to adapt to future conditions and regenerate naturally after disaster events.
Economic valuation data is contributing to better-informed decision making about coastal resources and development.
Although NBS methods are newer and not as well-tested or established as built infrastructure approaches, they are multi-purposed and provide a wealth of valuable co-benefits, including: sustaining tourism, livelihoods and local biodiversity; improving food security; sequestering carbon; and improving water quality. This is in contrast to conventional built-only measures that are purposed only to protect against disasters.

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References:

Sutton-Grier, A.E., K. Wowk, and H. Bamford. 2015. “Future of Our Coasts: The Potential for Natural and Hybrid Infrastructure to Enhance the Resilience of Our Coastal Communities, Economies and Ecosystems.” Environmental Science & Policy 51: 137–148.
Waite, R., L. Burke, and E. Gray. 2014. Coastal Capital: Ecosystem Valuation for Decision Making in the Caribbean. Washington, D.C.: World Resources Institute. http://www.wri.org/coastal-capital.
Image source: https://www.flickr.com/photos/synecdoche/18108618854/

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WORDS OF CAUTION

Photo credit: Flickr/Peter Counsell

Appropriate use of NBS is highly context specific, requiring careful evaluation, planning and design of project components

NBS are most effective when appropriately sited and designed. To the extent possible, planning and evaluation of NBS measures should assess synergies of the combination of gray and NBS, rather than viewing them as separate components.
Key principles to consider when planning nature-based solutions for climate change adaptation and disaster risk reduction include:

Beginning with a system-wide analysis of the local socio-economic, environmental, and institutional conditions.
Conducting thorough assessment of risks and benefits of the full range of possible measures, covering risk reduction benefits as well as social and environmental effects.
Using quantitative criteria to test, design, and evaluate nature-based solutions.
Using existing ecosystems, native species, and complying with basic principles of ecological restoration and conservation.
Using adaptive management based on long-term monitoring to ensure sustainable performance.

Implementing nature-based solutions requires consideration of biophysical and socio-economic processes on different scales in space and time. This requires consultation with a range of disciplines like hydrology, engineering, ecology, economics and social sciences, as well as participatory engagement with all relevant stakeholders. Implementation guidelines for successful solutions traverse a series of steps needed across the project cycle:

1. Define problem, scope and objective
2. Develop financing strategy
3. Conduct ecosystem, hazard and risk assessments
4. Develop nature-based risk management strategy
5. Estimate costs, benefits and effectiveness
6. Select and design the intervention
7. Implement and construct
8. Monitor and inform future practices

Considerable research needs still exist for:

Identifying the value of NBS for flooding and erosion protection services specifically;
Capturing the value of associated co-benefits, and what this means for return on investment.

The effectiveness of different NBS in providing particular services also needs to be better understood to comprehend what level of protection can be expected from which NBS in different contexts and geographies, and for what period of time given our rapidly changing climate.
However, for the past decade the World Bank has financed projects with NBS components around the world, and there is a growing evidence base of successfully implemented projects both in and outside the World Bank portfolio.

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References:

UNEP, IUCN, TNC, WRI, and U.S. Army Corps of Engineers. 2014. Green Infrastructure Guide for Water Management: Ecosystem-Based Management Approaches for Water-Related Infrastructure Projects. http://www.unepdhi.org/-/media/microsite_unepdhi/publications/documents/unep/web-unep-dhigroup-green-infrastructure-guide-en-20140814.pdf.
Sutton-Grier, A.E., K. Wowk, and H. Bamford. 2015. “Future of Our Coasts: The Potential for Natural and Hybrid Infrastructure to Enhance the Resilience of Our Coastal Communities, Economies and Ecosystems.” Environmental Science & Policy 51: 137–148.
Waite, R., B. Kushner, M. Jungwiwattanaporn, E. Gray, and L. Burke. 2015. “Use of Coastal Economic Valuation in Decision Making in the Caribbean: Enabling Conditions and Lessons Learned.” Ecosystem Services 11: 45–55. doi:10.1016/j.ecoser.2014.07.010.
World Bank. 2017. Implementing Nature-Based Flood Protection: Principles and Implementation Guidance. Washington, D.C: World Bank Publications. doi:10.1596/978-1-4648-0484-7.
Image: https://www.flickr.com/photos/durras/6088429152

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NBS FOR COASTAL FLOODING AND EROSION PROTECTION

Source: World Bank https://naturebasedsolutions.org/

1. Mangrove forests
2. Coral reefs
3. Oyster reefs
4. Sandy beaches and dunes
5. Coastal wetlands
6. Seagrass

To-date, World Bank clients and Task Team Leaders are more familiar with conventional built approaches or use NBS for purposes like biodiversity or nature conservation, water management, fishing and livelihood revitalization, other than specifically for disaster risk management objectives.
The vast majority of World Bank portfolio financial commitments still go to built infrastructure projects, and will continue to do so into the future. However, it is increasingly important to bring NBS out of obscurity, and into consideration as alternatives or complements to purely built infrastructure The rest of this presentation focuses on 6 NBS for addressing coastal flooding and erosion hazards, including specific risk reduction benefits, site requirements and implementation costs.

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References:

World Bank. Forthcoming. “Natural Hazards - Nature-Based Solutions.” Project Platform. Natural Hazards - Nature-Based Solutions. https://naturebasedsolutions.org/.

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1. MANGROVE FORESTS

Photo credit: Flickr/mopar05ram

Mangroves are species of trees and shrubs that live in coastal intertidal zones with low-oxygen soils and slow-moving waters

Approaches for implementation include:

Conserving existing mangroves
Enabling conditions for natural regeneration
Planting new mangrove forests

Mangroves are a type of trees and shrubs adapted to the coastal intertidal zone—the area above water at low tide and under water at high tide. They grow in areas with low-oxygen soil, where slow-moving waters allow fine sediments to accumulate. They only grow in tropical and sub-tropical latitudes, since they cannot withstand freezing temperatures.
Plant species in a mangrove community have special adaptations that allow them to survive the various levels of flooding and salinity in a coastal environment. Mangroves are characterized by their dense tangle of prop roots that make the trees appear to be standing on stilts above the water, which allow them to handle the daily rise and fall of tides. Most mangroves get flooded at least twice per day; their roots slow the movement of tidal waters, causing sediments to settle out of the water and build up the muddy bottom.
Implementation approaches for using mangroves as coastal protection include: conserving existing mangroves; enabling conditions for the natural regeneration of degraded mangrove systems; and planting new mangrove forests.
Two general categories of wetlands are typically recognized: coastal or tidal wetlands and inland or non-tidal wetlands. Tidal wetlands, and specifically mangroves—not salt marshes—are the wetland ecosystem focused on in this section.

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References:

Kathiresan, K., and B. L. Bingham. 2001. “Biology of Mangroves and Mangrove Ecosystems.” In Advances in Marine Biology, 40:81–251. Academic Press. doi:10.1016/S0065-2881(01)40003-4.
McOwen, C., J. van Bochove, and M. Jones. 2016. “Chapter 7.4 Extent of Mangroves and Drivers of Change.” In Large Marine Ecosystems: Status and Trends, 197–203. IOC-UNESCO and UNEP. Nairobi: UN Environment Programme,. http://onesharedocean.org/public_store/publications/lmes_report_chapters/TWAP_VOLUME_4_TECHNICAL_REPORT_Chapter7.4_1DEC2016.pdf.
Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
NOAA. 2017. “What Is a Mangrove Forest?” What Is a Mangrove Forest? https://oceanservice.noaa.gov/facts/mangroves.html.
US Dept. of Commerce. 2014. Oil Spills in Mangroves; Planning & Response Considerations. Washington, D.C: NOAA, National Ocean Service, Office of Response and Restoration. https://www.researchgate.net/publication/271193539_Oil_Spills_in_Mangroves_Planning_Response_Considerations.

Map accessible at Deltares 2014, found in US Dept of Commerce 2014
Image source: https://www.flickr.com/photos/7817806@N02/2793243924/in/photolist-5fQ771-mmVzDG-6tHFVh-7RK7Kb-bk1fAF-7trwqh-T9jkjn-T91FJM-ZcuTZL-UpQP1u-iy9vCt-21AZqTL-T9jjmk-66AWs2-T9jksP-W19F6y-NennFn-CRwZPo-T2BDXu-9yJpgA-TNJ3Pz-XioUte-SQoQmc-24MhA4c-Zs7FDS-SXuCYW-i24iqQ-UiGkGu-25eBLcV-dYGKSg-6ZFTTj-H6FfRA-SNptqW-YJdX95-U8W8kC-ZEzQTJ-ZAuEss-eRVuAr-dYpLyo-YNS7HF-5TbHTo-TBgKGx-m4kXxH-P6ogdj-221EwHj-9yiySc-Cs3y25-YS3DUk-pMGPCF-XzZHjL

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MANGROVE DISTRIBUTION AND NUMBER OF SPECIES

Graphic credit: US Dept. of Commerce 2014

Sources: McOwen et al. 2016; Kathiresan and Bingham 2001

70 species of mangroves grow in tropic and sub-tropical latitudes and approximately 123 countries and territories

About 70 species of mangroves exist, belonging to 20 families. Of them, only 1 mangrove species (the mangrove fern) is common to both hemispheres. Plant species found in mangrove forests other than the “true mangroves” are also important, and should be considered a part of the overall mangrove forest for the purposes of conservation management.
Mangroves worldwide cover an approximate area of 150,000 square kilometers of sheltered coastlines in the tropics and subtropics.
As can be seen in the figure on this slide, there are many more species prevalent in the Indo West Pacific than the Atlantic East Pacific.

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References:

Kathiresan, K., and B. L. Bingham. 2001. “Biology of Mangroves and Mangrove Ecosystems.” In Advances in Marine Biology, 40:81–251. Academic Press. doi:10.1016/S0065-2881(01)40003-4.
McOwen, C., J. van Bochove, and M. Jones. 2016. “Chapter 7.4 Extent of Mangroves and Drivers of Change.” In Large Marine Ecosystems: Status and Trends, 197–203. IOC-UNESCO and UNEP. Nairobi: UN Environment Programme,. http://onesharedocean.org/public_store/publications/lmes_report_chapters/TWAP_VOLUME_4_TECHNICAL_REPORT_Chapter7.4_1DEC2016.pdf.
Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
NOAA. 2017. “What Is a Mangrove Forest?” What Is a Mangrove Forest? https://oceanservice.noaa.gov/facts/mangroves.html.
US Dept. of Commerce. 2014. Oil Spills in Mangroves; Planning & Response Considerations. Washington, D.C: NOAA, National Ocean Service, Office of Response and Restoration. https://www.researchgate.net/publication/271193539_Oil_Spills_in_Mangroves_Planning_Response_Considerations.

Map accessible at Deltares 2014, found in US Dept of Commerce 2014

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RISK REDUCTION BENEFITS

Graphic credit: Spalding et al. 2014; World Bank 2016

Wave attenuation: speed and crest height reduction
Sediment trapping: shoreline stability and expansion, and soil elevation

Mangroves are estimated to reduce wave heights by an average of 31%

narayan

Mangrove forests stabilize the coastline, attenuating waves, storm surges, currents, and tides, thereby reducing erosion and flooding impacts.
Mangrove properties that affect their ability to attenuate waves and trap sediment include the width and length of mangrove forests, the size or height of trees and biomass, the tangled structure of dense aerial root systems, and interconnectivity with other coastal ecosystems. For example:

Wind and swell waves are rapidly reduced as they pass through dense biomass and root structures of mangrove forests, lessening wave damage during storms. Wind speeds are reduced; wave energy is attenuated and dissipated; wave height and peak water levels are mitigated; and the regeneration of waves is decreased.

Short-term wave height can be reduced by 13-66% per 100 meters of mangroves encountered, and 50-100% per 500 meters of mangroves encountered
Storm surge height can be reduced 5-50 cm/km.

Wide mangrove forests, ideally thousands of meters across, can be effective in reducing the flooding impacts of storm surges occurring during major storms—significantly reducing flood extent in low-lying areas. They reduce wind speeds, the impact of waves on top of storm surge and flooding impacts. Narrower mangrove belts, those that are hundreds of meters wide, can also produce these results, to a lesser degree.

Mangrove forest canopies have modified wind speeds by 85 percent at average wind speeds of five meters/second, and by 50 percent for average wind speeds of 15 percent or more.

Wide areas of mangrove forests can reduce tsunami heights, helping to reduce impacts to properties, and lives, from inundation of areas behind mangroves.

Mangroves can reduce tsunami flood depth, current velocity, tsunami pressure, hydraulic force, run-up height/distance, and inundation extent. For example, flood depth is expected to be reduced by 5 to 30 percent by mangrove belts that are several hundred meters wide.

The dense roots of mangroves help to bind and build soils, reducing erosion from storms, waves and tidal changes. The above-ground roots slow down water flows, encourage deposition of sediments and reduce erosion. Over time, mangroves can actively build up soils thereby increasing the thickness of the mangrove soil, which helps mitigate flooding as sea levels rise.
Sand dunes, barrier islands, saltmarshes, seagrasses and coral reefs can all play an additional role in reducing waves where mangrove forests are present.

On average, coastal habitats reduce wave heights between 35% and 71%. Coral reefs reduce wave heights by 70% (95% CI: 54–81%), salt-marshes by 72% (95%CI: 62–79%), mangroves by 31% (95% CI: 25–37%) and seagrass/kelp beds by 36% (95% CI: 25–45%).

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References:

Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.

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ADDITIONAL BENEFITS

Photo credit: Flickr/deslaco

Valuable forest products
Tourism and recreation
Fisheries
Water purification
Carbon sequestration
Biodiversity

Mangroves are among the most valuable ecosystems in the world, but have been lost and degraded in many parts of the world from logging, coastal development, spraying of herbicides, conversion to fish ponds, and from oil spills and other pollutants.
Beyond coastal risk reduction, these are among additional benefits presented by mangrove forests:

Forest products like timber and fuel woods. Mangrove trees produce dense, valuable wood, which is resistant to decay and to the impact of termites. Mangrove timber and poles have been used for centuries in house-building, while thinner “pole wood” is also valued for the building of fish-traps in mangrove waters. The same wood is important as fuel and for production of charcoal.
Fisheries and other commercially valuable food production. Mangroves are among the world’s most productive fishing grounds, yielding vast numbers of fish, crabs, shrimps and mollusks.
Tourism and recreation. Recreational fishing and tourism can be multi-million dollar industries in mangrove areas and neighboring ecosystems that have a mutual relationship with the health of the mangrove system.
Long-term carbon sequestration. Mangroves remove carbon dioxide from the atmosphere and store it in plant biomass and soils. Mangrove preservation is critical for long-term storage of soil and forest carbon, and destruction can lead to massive releases of carbon dioxide.
Biodiversity protection and health of other ecosystems. Birds, insects, mammals and marine creatures all inhabit mangrove ecosystems, and neighboring, mutual ecosystems like coral reefs and seagrass beds. For example, coral reefs are sensitive to excess sediments and nutrient pollution that can be exacerbated with mangrove degradation.

Mangrove removal is frequently justified on short-term economic grounds, but is often based on analysis that under-estimates the full ecosystem services and risk reduction benefits presented by mangrove forests, especially over the long term horizon or in light of heightened risk of erosion or flooding.
Communities, managers and planners need to take full account of all the services and functions of mangroves in order to understand the many benefits mangroves provide, and to consider the true cost incurred from losing or restoring mangrove forests.

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References:

Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
US Dept. of Commerce. 2014. Oil Spills in Mangroves; Planning & Response Considerations. Washington, D.C: NOAA, National Ocean Service, Office of Response and Restoration. https://www.researchgate.net/publication/271193539_Oil_Spills_in_Mangroves_Planning_Response_Considerations.
Photos: https://www.flickr.com/photos/robotbrainz/3222757923/in/photolist-6Wn3fA-5v83iX-6u9KXq-QUo1L3-76BS89-5FbkLt-q3VNT8-23aQR3J-q3PFRR-e1S3f3-R3Kpus-bQGjCT-UsQkYe-9yaaKD-9eYxWk-5UMtDM-4ezHeS-9mg8td-SYLv5q-5tkurv-4vBSLF-VqFPqW-9pvEth-bk1fAF-Zrian2-9mg5PU-23zoTDa-btgUqZ-21MMPR8-WFwqjj-YFyxmw-ecHanU-DcA5mT-pfPZ2e-5QU3rY-8HNJet-6KTV61-6gmDux-9jU2zC-UJ5LxC-VLM7n6-NennFn-Zi5k2w-Tj46EY-RNxJD7-r8vsML-e9JjWP-drQRSc-ZGrV8b-i24iqQ , https://www.nps.gov/bisc/learn/nature/mangroves.htm
Image source: https://www.flickr.com/photos/delasco/10871377094/in/photolist-hyEDE7-TvDyAM-Z8sneA-VCgg2t-XXeQia-6ohMrw-T29cSQ-b1gz16-T6wqKh-T1QCYF-24MhD2M-Ssrtxy-XGy7YX-9dJZqz-XRgw6T-23v6nAX-bEcaPV-RSqdJx-aLhK1p-gXHyB5-b5HiTR-dVreBH-D5jH77-Axf5us-8dEEsk-6iREmE-Yzd4VS-EX1M8-7hqcv9-bkbgPr-YZhx6L-Yd7UQZ-F3XD78-cXtxCj-23DQHUV-23Lgrh3-oHwbdG-SAWVra-DXQV6E-pyPemE-St6zWB-UEWTWE-buzggt-qjJiR4-Z9C9ih-dJWKmc-fsZfGe-Yzd5r1-VuPS7U-ozckE6

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CONSIDERATIONS FOR USING MANGROVES AS COASTAL DEFENSE

Sources: Spalding et al. 2014; Deltares 2016

Photo credit: Flickr/PNUD Panama

Integrate with other risk reduction measures
Incorporate valuation results into coastal planning and management decisions
Prevent conversion and maintain wide forests to extent possible
Leverage natural regeneration processes by restoring biophysical and social conditions
Follow and mimic nature in species selection and location if planting

Natural regeneration can occur in 15-30 years

Every coastline around the world is different, with unique hazards, associated exposure and vulnerability. The importance of mangroves in coastal defense and disaster risk reduction will depend both on the site characteristics and the local hazard context.
Mangroves can play a role in reducing risk in natural, rural, urban and even degraded settings, but are rarely stand-alone solutions and need to be appropriately combined with other risk reduction measures.
With regard to using mangroves as coastal defenses, guidance suggests:

Preventing mangrove conversion, and maintaining wide seaward mangroves forests/greenbelts to the extent possible. Allowing forestry and fisheries to the extent that it does not jeopardize the coastal risk reduction function or mangrove health in general.
Leveraging natural regeneration. Mangroves can recover in most areas, as long as ecological and social conditions are appropriate for mangrove recovery. While mangrove planting is hugely popular, it’s not always effective and many projects around the world suffer high failure rates, often times because of focus on a single species or improper placement according to tidal water level requirements. In many places it is not necessary to plant new mangroves, because mangroves can naturally recover. Restoring the natural patterns of water flow, preventing human disturbance and removing choking weed species may be enough to allow natural regeneration. In areas with erosion, mangrove restoration may require more active intervention such as protecting individual seedlings or restoring the sediment balance and hydrology.
Following and mimicking nature in species selection and location if planting. Natural mangrove forests are not monocultures – new forests will be more successful if they can replicate the density, structural complexity, and natural restocking of natural mangroves, using multiple native species with natural zonation. Planting of mangroves in the wrong places may destroy valuable ecosystems such as neighboring seagrass meadows and mudflats, which can reduce total risk reduction benefits.

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References:

Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
Deltares. 2016. Mangrove Restoration: To Plant or Not to Plant? https://www.deltares.nl/app/uploads/2016/07/Mangrove-restoration_to-plant-or-not-to-plant.pdf.
Lewis, R. R., and W. Streever (2000), Restoration of Mangrove Habitat. Tech Note ERDC TNWRP-VN-RS-3.2. Vicksburg: U.S. Army, Corps of Engineers, Waterways Experiment Station.
Image source: https://www.flickr.com/photos/155976344@N02/27125006899/in/photolist-HjWKwK-UznrDW-Hjk3Ta-WmzSHD-dPgCww-RRactu-aWaiW2-aWasaR-aWaeWr-aWbmer-aWbnPR-aW9y1V-aWodNx-aWb67K-aW9Ztc-aWbptF-aWak7e-aW9Hsa-aaoyjB-c4HNJU-dtL1aq-dtL1aN-aSwW8z-fCx9Fa-aWoK5c-c4HNDd-aWaWDx-cKf39U-fsfrc9-aWa8VR-21rpV1W-9gy3Bo-cwhAB1-mqguoJ-bDDqK7-cKeZMY-aarm1Y-fsfpcL-aarnWq-dcefse-aWoqJt-67kwoQ-fFmLGf-fs17BF-fsfrzj-JJJTac-dcAf1k-aar6Vf-dcegsy-fFmM5m

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WHAT DO MANGROVES COST?

Photo credit: Flickr/David Copeland

Sources: IFRC n.d.; Deltares 2016; Bayraktarove et al. 2015

Mangrove restoration can be 2-5x cheaper than submerged breakwaters for equivalent wave heights up to half a meter

Median mangrove restoration cost estimate value is ~US$9,000/hectare

Some of the most cost-effective solutions to consider are reducing threats and preventing mangrove loss from happening in the first place; and improving existing management of mangroves rather than having to invest in mangrove rehabilitation or restoration in the future.
Median mangrove restoration cost estimate value is US$8,961/hectare, according to Bayraktarove et al. 2015. Restoration cost is represented at US$ 2010/ha.

Compared with other ecosystems, mangrove restoration projects are typically the largest and the least expensive per hectare. Coral reefs and seagrass are among the most expensive ecosystems to restore. For coral reefs, seagrass, saltmarshes, and oyster reefs, only small‐scale restoration efforts of <1 ha have been documented. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, is highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%).

A couple of examples of mangrove costs include examples from successful projects in Vietnam and Indonesia, which feature different scales of operation and different practices—the planting of mangrove plantations and Ecological Mangrove Restoration which relies on capacity building and natural regeneration approaches. It is unclear what date these cost estimates are reported in.

Indonesia. Between 1990-2004, 1,200 hectares of mangrove forest was converted into aquaculture ponds on Tanakeke Island in Indonesia. The ponds became unproductive, and villagers began to rehabilitate their mangroves for their fisheries and storm protection values. Ecological Mangrove Rehabilitation, which combines hydrological rehabilitation with ecological enhancement and in this specific case included strategic breaching of dike walls, re-creation of tidal creeks, periodic dispersal of mangrove buds and a minimal amount of planting, has been achieved on over 530 hectares. The total direct cost of rehabilitation amounted to 690,000 USD for design, implementation, management and monitoring, or US$1,300 USD per hectare.
Vietnam. A community-based ‘Mangrove Plantation and Disaster Risk Reduction’ (MP/DRR) project in the disaster prone coastal provinces of northern Vietnam was implemented over 17 years from 1994-2010 to help protect the region from climate-related vulnerabilities like sea level rise and intensifying storm patterns. Mangrove stands were planted on 8,961 hectares amounting to US$843 per hectare.

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References:

Bayraktarov Elisa, Saunders Megan I., Abdullah Sabah, Mills Morena, Beher Jutta, Possingham Hugh P., Mumby Peter J., and Lovelock Catherine E. 2015. “The Cost and Feasibility of Marine Coastal Restoration.” Ecological Applications 26 (4): 1055–1074. doi:10.1890/15-1077.
Spalding, M., A. McIvor, F.H. Tonneijck, S. Tol, and P. van Eijk. 2014. Mangroves for Coastal Defence Guidelines for Coastal Managers & Policy Makers. The Nature Conservancy, University of Cambridge, Wetlands International. https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf.
IFRC. n.d. “Mangrove Plantation in Viet Nam: Measuring Impact and Cost Benefit.” http://www.ifrc.org/Global/Publications/disasters/reducing_risks/Case-study-Vietnam.pdf.
Deltares. 2016. Mangrove Restoration: To Plant or Not to Plant? https://www.deltares.nl/app/uploads/2016/07/Mangrove-restoration_to-plant-or-not-to-plant.pdf.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.
Image source: https://www.flickr.com/photos/davetron5000/2295531386/in/photolist-4uRcvm-WbWpLR-ZDtLxB-bzBJ79-T6wqeN-UuTjXA-hidoZN-9qALD2-SUkamv-VrwgVj-UzMNTb-dNBtUE-ZVc7Le-5LqRPU-fKdz7K-dtvy8v-244K4dL-FTtee2-7JCXb-qGvwBx-8RkEy3-ZdtE7m-T9Zqhh-dEAAY6-Vs93mh-ioUQHH-RPimrB-guzDju-m4preC-nnQTJb-fge8YK-WMEnJi-edYw2F-qhBsSo-duQhd9-FWMjcd-a5X7P1-m4npBy-6ZgEkb-TqsStJ-Tv2UEP-cw1Z65-23Jh4zT-6ZcEM8-Rc51BA-dU2NKt-Xcfsm3-9GaVqD-dU87sJ-YqpJ4c

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DISASTER RISK MANAGEMENT WITH MANGROVE PLANTATION IN VIETNAM

Source: IFRC n.d.

US$15 million in total avoided risk savings
US$80,000-295,000 reduced storm damages to dike system
200-800% additional income for beneficiary communities

The Vietnam MP/DRR project is funded by the Intl. Federation of Red Cross and Red Crescent societies, and implemented by Viet Nam Red Cross. It has had significant impacts reducing disaster risk and enhancing communities’ livelihoods.

Overall costs for the project, spanning 17 years, stands at US$ 8.88 million. This has supported the creation of 8,961 hectares of mangrove forests in 166 communities, and the protection of approximately 100km of dike lines.
350,000 beneficiaries were reached directly by the project’s intervention, while another two million were indirectly protected through the afforestation efforts.
Comparing the damage caused by similar typhoons before and after the intervention, damages to dikes were reduced by US$80,000-US$295,000 due to the mangroves. A total savings due to avoided risks in the communities was approximately US$15 million.
The mangroves also helped coastal economies through an increase in per hectare yield of aquaculture products such as shells and oysters by 209-789 percent. Direct economic benefits from aqua product collection, honeybee farming, etc., were found to be between USD$344,000-6.7 million in the selected communes.

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References:

IFRC. n.d. “Mangrove Plantation in Viet Nam: Measuring Impact and Cost Benefit.” http://www.ifrc.org/Global/Publications/disasters/reducing_risks/Case-study-Vietnam.pdf.

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2. CORAL REEFS

Photo credit: Flickr/Eric Baker

Source: Paulay 1997; Burke et al. 2011

Coral reefs are limestone-like physical structures built up in tropical waters from deposits made by ~800 species of reef-building corals and other algae organisms

Approaches for implementation include:

Conserving integrity of existing reefs
Repairing reef structural integrity (width/height)
Recovering the coral species diversity and structure, transplanting from farms or donor sites
Using nature-based artificial material structures—e.g., reef balls, bio-rock, eco-reefs

A coral reef is both a physical structure and a diverse ecosystem. The physical structure is built up from the sea bed over centuries or millennia through the accumulated deposition of limestone-like (calcium carbonate) skeletons, laid down by reef-building corals and other organisms, such as coralline red algae.

There are approximately 800 species of reef-building corals inhabit tropical oceans. Individual coral animals, known as polyps, live in compact colonies of many identical individuals and secrete calcium carbonate to form a hard skeleton. Corals produce colonies in a multitude of shapes—huge boulders, fine branches, tall pillars, leafy clusters—and vibrant colors. These colonies build around and on top of one another, while sand and rubble fill the empty spaces. Calcareous algae also contribute by “gluing” together the matrix to form a solid three-dimensional structure.

Coral reefs are found in the shallow seas of the tropics and subtropics, occur to depths of about 50 meters (with the majority of coral growth often found at 10 to 20 meters), and are often described by the shape of the structures they build. For example:

Fringing reefs follow the coastline, tracing the shore tens or hundreds of meters from the coast.
Barrier reefs lie far offshore, separated from the coast by wide, deep lagoons.
Although deep water coral reefs exist, they are at depths irrelevant for disaster risk mitigation.

Active restoration actions relevant to maintaining or improving the coastal defense service of coral reefs include biological restoration, physical restoration, and artificial reefs.

Biological restoration consists of recovering or rebuilding coral species diversity and structure of degraded reef-coral ecosystems. This includes direct in-situ transplantation of stony corals from donor reef sites to degraded sites; and seeding coral gametes and sperm collected during spawning from a small coral spat to the degraded reef site from a lab or nursery.
Physical restoration consists of repairing or adding to the reef’s structural integrity (the reef’s width and height) with some combination of limestone and cement. Acute physical impacts to the reef crest from coral mining, ships, etc. that fracture the limestone matrix or cause craters and loss of live coral need to be countered with active physical restoration interventions to prevent further degradation of reef-crest surface.
Artificial reefs consists of placing structures like limestone blocks, rock piles, molded cement, steel, and other materials on the seafloor. When used for coastal defense, artificial structures immediately provide direct and short-term wave and erosion reduction benefits.

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References:

World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.
Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C.: World Resources Institute. http://pdf.wri.org/reefs_at_risk_revisited.pdf.
Paulay, G. 1997. “Diversity and Distribution of Reef Oganisms.” In Life and Death of Coral Reefs. New York. https://www.researchgate.net/publication/289014192_Diversity_and_Distribution_of_Reef_Organisms.
Image source: https://www.flickr.com/photos/chericbaker/15615379761/in/photolist-8gmp4F-5eTPyL-pMSUnx-nGidzx-FVJir-9xTJYm-8gpowC-9vWQs3-88gter-sjrMG7-8RUqiP-9xQL5v-VS4WDm-53ayLP-VRBDyx-8gmsqn-6qgHjc-53eS9m-cHYAN-5ddJFu-VZ73Eb-Xx4jj8-pN7CcT-2EpVoB-5ePrDa-VysQyA-oRg2L9-dNoQtB-PQWTgQ-8JBY6Z-8RXw7m-8gmfPa-2zsjT6-6qgHRe-poM2Xe-pEfbi8-cjvKG7-7vhMY-9ZkQx7-nxLhyQ-reGRfD-oft9X5-cJ6cj-8gpvHb-7VRR6E-pN7CNn-53aArH-oKTgBa-axzMto-jaSjQd

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CORAL REEFS OF THE WORLD CLASSIFIED BY LOCAL THREAT LEVEL��

Source: McAllister 1995; Burke et al. 2011

Coral reefs cover 250,000 km²
75% are threatened by local human activities (e.g., overfishing, pollution) and global climate-related stressors combined

Coral reefs exist within a narrow belt across the world’s tropical oceans, where local conditions—climate, marine chemistry, ocean currents, and biology—combine to meet the exacting requirements of reef-building corals. The world’s coral reefs cover an area of approximately 250,000 sq. km, roughly the size of the United Kingdom, with the highest concentrations in Southeast Asia and the Pacific.
As of 2007, more than 275 million people lived within 30 km of reefs, or less than 10 km from the coast, many of which were in developing countries and island nations where dependence on coral reefs for food and livelihoods is very high.
More than 60% of the world’s reefs are under immediate and direct threat from one or more local sources such as overfishing, coastal development, and pollution. The most pervasive local threat affecting 55% of the world’s reefs is over-and destructive fishing, while 25% of reefs are affected by coastal development and watershed-based pollution respectively.
75% of coral reefs are classified as threatened when you consider global thermal stressors like rising ocean temperatures, which are linked to widespread weakening and mortality of corals due to mass bleaching. By 2030, 90% of reefs will be threatened with nearly 60 percent facing high, very high, or critical threat levels.

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References:

Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C.: World Resources Institute. http://pdf.wri.org/reefs_at_risk_revisited.pdf.
World Resources Institute. 2013. “Reefs at Risk--Online Global Reefs Map.” Online Global Reefs Map. http://www.google.com/fusiontables/embedviz?viz=MAP&q=select%20col0%2C%20col1%2C%20col2%2C%20col3%2C%20col4%20from%20434275%20&h=false&lat=20&lng=0&z=1&t=3&l=col4.
McAllister, D. 1995. “Status of the World Ocean and Its Biodiversity.” Sea Wind 9: 1–72.

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RISK REDUCTION BENEFITS

Graphic Source: World Bank 2016

Mitigate wave energy, diminishing speed and crest height
Reduce associated erosion and wave-induced flooding

Coral reefs are estimated to reduce wave heights by an avg. 70% and wave energy by 75-95%

Coral reefs play a valuable role in buffering coastal communities and infrastructure from the physical impacts of wave action and storms, thereby reducing coastal erosion and lessening wave-induced flooding.
Physical structures of coral reefs are estimated to protect 150,000 km of shoreline in more than 100 countries and territories. Shallow coral reefs, in water depths less than 5 meters, play the largest role in wave attenuation and coastal defense.
Coral reefs function similarly to submerged or low-crested built breakwater structures. They protect shorelines by absorbing and dispersing a significant part of the wave energy that otherwise would be transmitted onshore. Coral reefs typically mitigate 75 to 95 percent of wave energy, but are less effective for large waves or storm surges during storm events.

This mainly occurs by breaking waves at the seaward edge of the reef and through bottom friction as the waves cross the reefs. Reefs dissipate wave energy, reducing routine erosion and lessening inundation and wave damage during storms. This function protects human settlements, infrastructure, and valuable coastal ecosystems such as seagrass meadows and mangrove forests.

The degree of shoreline protection, wave dispersion and attenuation benefits provided by reefs will vary with the coastal context. Important factors include the nature of the land protected (e.g., geology, vulnerability to erosion, and slope), the nature of the coral reef (depth, continuity, and distance from shore), and local storm and wave regimes.

For example: the location and morphology of zones of coral development—from offshore to inshore, including fore reef, reef crest reef flat, and back reef zones—are the result of antecedent topography, as well as the interplay between coral growth and wave energy.

Coastal defense functions of reefs will continue if reef accretion (i.e., growth) keeps pace with rising waters. However, the timescales for how changes in coral reef condition will influence whole-reef accretion dynamics and shoreline protection is not well understood because of high spatial and temporal variability in the coral erosion and deposition processes.
Improvements to methodologies and higher resolution data sets are still needed to allow for better accounting of a coral reef’s true economic “risk reduction” value.
On average, coastal habitats reduce wave heights between 35% and 71%. Coral reefs reduce wave heights by 70% (95% CI: 54–81%), salt-marshes by 72% (95%CI: 62–79%), mangroves by 31% (95% CI: 25–37%) and seagrass/kelp beds by 36% (95% CI: 25–45%).

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References:

World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.
Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C.: World Resources Institute. http://pdf.wri.org/reefs_at_risk_revisited.pdf.
Brander, R.W., P. Kench, and D. Hart. 2004. “Spatial and Temporal Variations in Wave Characteristics across a Reef Platform, Warraber Island, Torres Strait, Australia.” Marine Geology 207: 169–184.
Ferrario, Filippo, Michael W. Beck, Curt D. Storlazzi, Fiorenza Micheli, Christine C. Shepard, and Laura Airoldi. 2014. “The Effectiveness of Coral Reefs for Coastal Hazard Risk Reduction and Adaptation.” Nature Communications 5. doi:10.1038/ncomms4794.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.

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ADDITIONAL BENEFITS

Source: Spalding et al. 2017 (graphic); Burke et al. 2011

Livelihoods
Fisheries
Tourism
Medicine
Biodiversity

Very high >US$365,000/km²

High

Medium

Low

Very low <US$8,000/km²

No value

US$36 Billion Annually from Tourism

Aside from coastal protection, these dynamic and highly productive coral reef systems are a critical habitat for numerous species and provide essential ecosystem services—food, medicine, cultural and aesthetic value—upon which millions of people depend.
For example:

Tourism and cultural heritage. 30% of the world's reefs are of value in the tourism sector, with their total value estimated at nearly US$36 billion.
Livelihoods and food supply. Many of the millions of people depend on coral reefs for food and livelihoods. Reef-associated fish species are an important source of protein, contributing about one-quarter of the total fish catch on average in developing countries. A healthy, well-managed reef can yield between 5 and 15 tons of fish and seafood per square kilometer per year.
Biodiversity. Although coral reefs span less than one-tenth of one percent of the entire global marine environment, they are thought to contain about 25 percent of the ocean’s entire biodiversity. They are nursing and breeding grounds for reef-associated species (e.g. tuna, mackerel), reef fishes (e.g. snappers, groupers, parrot fishes), large invertebrates (giant clams, conch, lobsters, crabs) for fisheries industry and aquarium trade.
Treatments for disease. Many reef-dwelling species have developed complex chemical compounds that harbor the potential for forming the basis of life-saving pharmaceuticals, such as treatments for cancer, HIV, malaria, and other diseases.

The loss of tropical coral reefs to acidification could cost $1 trillion by 2100 in terms of lost shoreline protection and lost revenues for the tourism and food industries. Understanding the full value of coral reefs and the spatial distribution of these values, provides an important incentive for sustainable reef management.

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References:

Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C.: World Resources Institute. http://pdf.wri.org/reefs_at_risk_revisited.pdf.
Spalding, Mark, Lauretta Burke, Spencer A. Wood, Joscelyne Ashpole, James Hutchison, and Philine zu Ermgassen. 2017. “Mapping the Global Value and Distribution of Coral Reef Tourism.” Marine Policy 82: 104–113. doi:10.1016/j.marpol.2017.05.014.
US Commission on Ocean Policy. 2004. An Ocean Blueprint for the 21st Century Final Report. Washington, D.C.: US Commission on Ocean Policy.
Secretariat of the Convention on Biological Diversity. 2014. An Updated Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. CBD Technical Series 75. Montreal: UNEP, Convention on Biological Diversity. http://www.deslibris.ca/ID/244312.

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CONSIDERATIONS FOR USING CORAL REEFS AS COASTAL DEFENSE

Photo: Kanenori / Pixabay

Effectively manage and protect existing reefs
Integrate coral restoration with other structural and non-structural risk reduction strategies
Incorporate valuation results into coastal planning and management decisions
Reduce local and global threats

Corals can take 3-8 years to reach sexual maturity

Coral reefs are shown to be efficient natural breakwaters that can form an important first line of defense against natural threats for coastal nations. Estimates indicate that more than 200 million people benefit from reduced risk of coastal flooding as a result of coral reefs.
With regard to using coral reefs as risk management, guidance suggests:

Effectively manage and protect existing reefs. While over one quarter of the world’s coral reefs, or 27%, are within marine protected areas (MPAs), many are ineffective or only offer partial protection. More than half of reefs in MPAs are in Australia alone. Only 6% of the world’s coral reefs are located in effectively managed MPAs. Furthermore, MPA coverage is strongly biased and located away from areas of greatest threat, limiting their potential for reducing threats in areas of heavy human pressure. In addition to effective conservation areas, improved fisheries management and incorporation of reef-related concerns into coastal planning and watershed management can also help protect and better manage existing reefs.
Incorporate coral restoration with other non-structural management strategies. Coupling active restoration with improved reef management strategies tackling issues like water quality, overfishing, and habitat protection is essential for long-term restoration success. Coral restoration efforts include biological restoration, physical restoration and artificial reefs:

Biological restoration consists of recovering or rebuilding coral species diversity and structure of degraded reef-coral ecosystems. This includes direct in-situ transplantation of stony corals from donor reef sites to degraded sites; and seeding coral gametes and sperm collected during spawning from a small coral spat to the degraded reef site from a lab or in-situ nursery.
Physical restoration consists of repairing or adding to the reef’s structural integrity (the reef’s width and height) with some combination of limestone and cement. Acute physical impacts to the reef crest from coral mining, ships, etc. that fracture the limestone matrix or cause craters and loss of live coral need to be countered with active physical restoration interventions to prevent further degradation of reef-crest surface.
Artificial reefs consists of placing structures like limestone blocks, rock piles, molded cement, steel, and other materials on the seafloor. When used for coastal defense, artificial structures immediately provide direct and short-term wave and erosion reduction benefits.

Incorporate coral enhancement with other structural measures in defense designs. This includes built or artificial solutions and other ecosystems like mangroves and seagrasses. There is a growing recognition within the coastal engineering field that building with nature, as opposed to against it, can provide significantly greater benefits overall.

Combining coral enhancement and nature-based artificial material structures—e.g., reef balls, biorock, ecoreefs—into sustainable coastal defense designs can provide multiple benefits over traditional gray designs. Although there will be tradeoffs compared to traditional breakwaters, these more natural submerged breakwaters can still provide significant wave protection and beach sand retention benefits with the added benefits of fisheries production, tourism, and biodiversity.
Corals in combination with mangroves or seagrasses have been found to increase coastal protection, mostly in fringing reefs and non-storm conditions. During storms events, corals do not largely contribute to coastal protection from large waves and storm surge.

Incorporate valuation studies into decision-making. Many human pressures on coral reefs arise from decisions that fail to take full range of ecosystem values and benefits into account. Economic valuation can contribute to better-informed decision making about coastal resource use and development. There are a number of procedural measures valuation practitioners can employ to do more to ensure valuation studies inform decision-making, including: strong stakeholder engagement; identification of causal links; strategy for widespread and targeted dissemination; strategic packaging of results; and identification and execution within advantaged timeline.

It can take corals from 3-8 years to reach sexual maturity, which is important to consider when evaluating the timeliness of this approach to risk reduction. Many different kinds of corals make up a coral reef, and each kind grows at different speeds. Some grow very slowly (less than 2 mm per year, or 1/10th of an inch), but others can grow much faster, up to 10 cm per year (or 4 inches). The age at which sexual maturity is reached depends upon the species of coral selected. With the use of a simple in situ nursery, some corals have been reared to a transplantable size and to reproductive maturity in 3 years. However, massive brain corals famous for their size and longevity, take 8 years to reach sexual maturity.

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References:

World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.
US Army Corps of Engineers. 2013. Coastal Risk Reduction and Resilience. http://www.swg.usace.army.mil/Portals/26/docs/PAO/Coastal.pdf.
Burke, L., K. Reytar, M. Spalding, and A. Perry. 2011. Reefs at Risk Revisited. Washington, D.C.: World Resources Institute. http://pdf.wri.org/reefs_at_risk_revisited.pdf.
Waite, Richard, Benjamin Kushner, Megan Jungwiwattanaporn, Erin Gray, and Lauretta Burke. 2015. “Use of Coastal Economic Valuation in Decision Making in the Caribbean: Enabling Conditions and Lessons Learned.” Ecosystem Services 11: 45–55. doi:10.1016/j.ecoser.2014.07.010
National Science Foundation. 2005. “UCSB Science Line.” http://scienceline.ucsb.edu/getkey.php?key=849.
Cooke, C., and R. Fransham. 2016. Implementation Strategy for Coral Reef Transplantation Methods in Support of Natural Resource Planning, Management and NEPA. San Diego, CA: SPAWAR.
Baria, Maria Vanessa B, Dexter W dela Cruz, Ronald D Villanueva, and James R Guest. 2012. “Spawning of Three-Year-Old <I>Acropora Millepora</I> Corals Reared from Larvae in Northwestern Philippines.” Bulletin of Marine Science 88 (1): 61–62. doi:10.5343/bms.2011.1075.
Image source: https://pixabay.com/en/coast-coral-reefs-transparency-2253105/

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WHAT DO CORAL REEFS COST?

Graphic Credit: World Bank 2016

Source: Bayraktarove et al. 2015

Median cost of restoring coral reefs is estimated to be ~US$165,600 per hectare

Cost of structural restoration measures can be significantly less expensive than building tropical breakwaters

Reducing threats to coral reefs and improving management efforts offer the most cost-effective solutions to retaining a reef’s coastal protection services. Depending on the circumstances, the restoration of coral reefs can also be more cost-effective than building artificial structures, but it is very important to consider how long the benefits of coral restoration efforts versus other measures will last over time and that only small-scale restoration efforts have been documented. For example, the cost of constructing a tropical breakwater per linear foot is estimated to be US$5,000-10,000, whereas the cost of reef restoration has been found to range from US$.2k – 508k/linear foot.
The median cost of restoring coral reefs is estimated to be US$165,607/hectare, according to Bayraktarove et al. 2015. Restoration cost is represented at US$ 2010/ha.

Compared with other ecosystems, coral reefs and seagrass are among the most expensive ecosystems to restore. For coral reefs, seagrass, saltmarshes, and oyster reefs, only small‐scale restoration efforts of <1 ha have been documented. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, is highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%).

Regarding structural reef restoration efforts, analysis of US Army Corps of Engineer projects has shown the cost of structural restoration measures are significantly less expensive than building tropical breakwaters. For example, the typical costs of building tropical breakwaters ranges from US$456-US$188,817 per meter with a median project cost of US$19,791 per meter, but the costs of structural coral reef restoration projects were US$20-US$155,000 per meter with a median project cost of US$1,290 per meter
However, regarding biological restoration, the costs and benefits of these techniques vary. Many techniques are still being researched, and are not yet adopted by managers and policy makers.
A key question for investing in coral reefs specifically for risk reduction benefits surrounds whether the reefs can keep up with sea level rise and are resilient to changing thermal waters to be a long-term valuable investment compared to alternative risk reduction interventions.

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References:

Bayraktarov Elisa, Saunders Megan I., Abdullah Sabah, Mills Morena, Beher Jutta, Possingham Hugh P., Mumby Peter J., and Lovelock Catherine E. 2015. “The Cost and Feasibility of Marine Coastal Restoration.” Ecological Applications 26 (4): 1055–1074. doi:10.1890/15-1077.
World Bank. 2016. Managing Coasts with Natural Solutions Guidelines for Measuring and Valuing the Coastal Protection Services of Mangroves and Coral Reefs. Washington, D.C.: Wealth Accounting and the Valuation of Ecosystem Services Partnership (WAVES). http://documents.worldbank.org/curated/en/995341467995379786/pdf/103340-WP-Technical-Rept-WAVES-Coastal-2-11-16-web-PUBLIC.pdf.
Ferrario, Filippo, Michael W. Beck, Curt D. Storlazzi, Fiorenza Micheli, Christine C. Shepard, and Laura Airoldi. 2014. “The Effectiveness of Coral Reefs for Coastal Hazard Risk Reduction and Adaptation.” Nature Communications 5. doi:10.1038/ncomms4794.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Image: https://upload.wikimedia.org/wikipedia/commons/d/df/Reef_Snorkelling_on_the_Great_Barrier_Reef.jpg

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DISASTER RISK MANAGEMENT WITH CORAL REEF RESTORATION IN BELIZE

Graphic: nps.gov

Project Locations in Yellow

Objective: build on artificial reef creation successes to strengthen climate resilience, reduce flooding and erosion
Cost: US$300,000 for coral activities out of US$6 million project budget
Expected outcome: reefs will help decrease overall wave action

The Adaptation Fund & World Bank are financing and implementing the Marine Conservation & Climate Adaptation Project (MCCAP) in Belize from 2015-2020. This project features activities in marine protected areas and is modeled after successful coral activities by Fragments of Hope projects, which transplanted corals in Laughing Bird Caye in 2010. The corals outplanted spawned in 2015 and 2016, which is sign of great success.
The Government of Belize’s objective with the MCCAP project is to strengthen climate resilience, reduce flooding and erosion by restoring coral reefs to the Belize Barrier Reef System. The project builds on successful artificial reef creation started by the Interamerican Development Bank and Fragments of Hope to cope with coral bleaching and disease.
The project will be active in 3 Marine Protected Areas (MPAs) from 2015 to 2020 and consist of US$6 million budget. Approximate cost of coral activities is US$300,000.

Locations: The project is active in the Corozal Bay Wildlife Sanctuary, Turneffe Atoll Marine Reserve and South Water Caye Marine Reserve. Turneffe atoll provides an estimated US$38 million/year in shoreline protection services.
Project activities include: rearing of coral fragments in rope nurseries, followed by transplantation to destination reef and re-population of reef-associated fish species. Six nursery tables in two Marine Protected Areas (MPA) will be established, as well as a grants program to diversify livelihoods (e.g. seaweed farming, slope fishing, agriculture have been requested). The project works with communities to tackle impacts of 1) climate change and 2) the extension of the MPA replenishment zones on local fisheries to strengthen overall MPA governance, and extend replenishment zones.
Expected outcomes: the project will decrease overall wave action.

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References:

Documentation of project details provided by World Bank GFDRR.
Image source: https://www.nps.gov/bisc/planyourvisit/index.htm

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3. OYSTER REEFS AND BEDS (REEFS)

Photo credit: Flickr/Bas Kers

Oyster reefs are intertidal or subtidal dense colonies of both living and dead oyster structures formed in brackish or marine waters

Approaches for implementation include:

Conserving integrity of existing reefs
Restoring natural reefs
Constructing new reef structures at former historic reef sites

Oyster reefs and beds or bars (hereafter called “reefs”) are dense colonies of both living and dead oysters that form from individual oysters growing upward and outward. The structures accrete through the continuing deposition of shell material. An oyster reef system includes connected reefs or beds, and may also include small areas of bare mud, sand or shelly substrates or seagrass.
Oyster reefs can be intertidal or subtidal, and are found in brackish to marine waters. One or a few species of oysters can produce reef habitat for an entire ecosystem. As successive generations of oysters settle and grow, reefs become highly complex, with many structural irregularities and infoldings that provide a wealth of microhabitats.
Historically, they were a dominant structural and ecological component of estuaries around the globe, and fueled coastal economies for centuries.
Oyster restoration projects can take many forms and use a variety of construction materials. The aim can be restoring a natural reef, or constructing a new reef structure at former historic reef sites. Materials for restoring or construction may include unconsolidated clean shell transfer (cultch), bagged clean shells, limestone or fossil shells, engineered concrete domes, or other similar materials. Methods for construction include direct placement of cultch or other materials to form a reef specific design, or spraying unconsolidated shell off transport barges across a project area resulting in a reef with large spatial extent, but varying vertical relief and cultch density.

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References:

Baggett, L.P., S.P. Powers, R. Brumbaugh, L.D. Coen, B. DeAngelis, J. Greene, B. Hancock, and S. Morlock. 2014. Oyster Habitat Restoration Monitoring and Assessment Handbook. Arlington, VA, USA: The Nature Conservancy. https://www.conservationgateway.org/ConservationPractices/Marine/Documents/Oyster%20Habitat%20Restoration%20Monitoring%20and%20Assessment%20Handbook.pdf.
Beck, Michael W., Robert D. Brumbaugh, Laura Airoldi, Alvar Carranza, Loren D. Coen, Christine Crawford, Omar Defeo, et al. 2011. “Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management.” BioScience 61 (2): 107–116. doi:10.1525/bio.2011.61.2.5.
Burrows, F., J.M. Harding, R. Mann, R. Dame, and L. Coen. 2005. “Chapter 4. Restoration Monitoring of Oyster Reefs.” In Science-Based Restoration Monitoring of Coastal Habitats, Volume Two: Tools for Monitoring Coastal Habitats. Vol. 2. National Coastal Ocean Program Decision Analysis Series. Silver Spring, MD: NOAA/National Centers for Coastal Ocean Science/Center for Sponsored Coastal Ocean Research. http://www.oyster-restoration.org/wp-content/uploads/2012/06/Volume2ch4oys.pdf.
Hill, K. 2002. “Oyster Reef Habitats.” Smithsonian Marine Station. https://www.sms.si.edu/IRLSpec/Oyster_reef.htm.
Image: https://www.flickr.com/photos/21933510@N07/3852026552

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GLOBAL CONDITION OF OYSTER REEFS IN BAYS AND ECOREGIONS

Source: Beck et al 2011

85% of the world’s oyster reef ecosystems have been lost from overharvesting, pollution and habitat loss

Today, while individual oysters are still present in most places many reefs that were once common are now rare or extinct.
Global analysis estimates that over the past 100 years, 85% of the world's oyster reefs have been lost and many other reefs are functionally extinct—unable to fulfill their historic ecological and economic roles in most bays and tributaries worldwide.
The driving forces behind their decline include destructive fishing practices, coastal overdevelopment, poorly managed aquaculture and poor water quality. These systems are also susceptible, like coral reef ecosystems, to rising ocean temperature and resulting acidification.
Evidence suggests that, historically, restrictions were indeed placed on harvests and there was concern about the incidence of disease and environmental degradation, but in the vast majority of cases harvests continued until oysters could no longer be commercially fished.

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References:

Beck, Michael W., Robert D. Brumbaugh, Laura Airoldi, Alvar Carranza, Loren D. Coen, Christine Crawford, Omar Defeo, et al. 2011. “Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management.” BioScience 61 (2): 107–116. doi:10.1525/bio.2011.61.2.5.

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RISK REDUCTION BENEFITS

Graphic credit: TNC 2018

Protect adjacent habitats with risk reduction properties
Reduce wave energy
Enhance shoreline stability, expansion and elevation

Oyster reefs in Alabama have reduced wave heights on average 53-91%

Oyster reefs can serve as natural coastal buffers, absorbing wave energy directed at shorelines and reducing erosion caused by waves, sea-level rise, and storms, much like a constructed breakwater would. For example:

Reduced wave energy. The physical structure of oyster reefs alter water flow patterns and attenuate waves, reducing the wave force. They are most effective for low or moderate wave energy events, rather than storm surge flooding. For example, in Mobile Bay, Alabama, 5.85 km of restored reefs reduce the height and energy at shoreline of the average and top 10% of waves by 53-91% and 76-99%, respectively.
Trapping and accumulation of sediment. The lessening of wave action allows sediments to accumulate inshore (landward) of the reef, stabilizing and raising the shoreline. This shoreline stabilization and sediment accumulation can benefit nearby marsh and other habitats by both protecting the marsh from erosion and even possibly allowing the marsh to expand due to the accretion of sediments. This also helps spare lowlands from flooding.
Protect adjacent habitats that add risk reduction benefits. Oyster reefs can protect tidal sand flats and marsh edges, potentially also aiding in the creation or protection of seagrass or other submerged aquatic vegetation through sediment stabilization and improvements in water quality that often occur as oysters filter water. This, in turn, further enhances the flooding and erosion protection properties of the shoreline because of the compounded effects of these ecosystems working together to stabilize sediment and attenuate floodwaters.

Although they now occupy a small fraction of their prior distribution, the restoration, recovery and sustainable management of oyster reefs are possible.

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References:

Rodriguez, Antonio B., F. Joel Fodrie, Justin T. Ridge, Niels L. Lindquist, Ethan J. Theuerkauf, Sara E. Coleman, Jonathan H. Grabowski, et al. 2014. “Oyster Reefs Can Outpace Sea-Level Rise.” Nature Climate Change 4 (6): 493–497. doi:10.1038/nclimate2216.
Ridge, Justin T., Antonio B. Rodriguez, F. Joel Fodrie, Niels L. Lindquist, Michelle C. Brodeur, Sara E. Coleman, Jonathan H. Grabowski, and Ethan J. Theuerkauf. 2015. “Maximizing Oyster-Reef Growth Supports Green Infrastructure with Accelerating Sea-Level Rise.” Scientific Reports 5. doi:10.1038/srep14785.
Baggett, L.P., S.P. Powers, R. Brumbaugh, L.D. Coen, B. DeAngelis, J. Greene, B. Hancock, and S. Morlock. 2014. Oyster Habitat Restoration Monitoring and Assessment Handbook. Arlington, VA, USA: The Nature Conservancy. https://www.conservationgateway.org/ConservationPractices/Marine/Documents/Oyster%20Habitat%20Restoration%20Monitoring%20and%20Assessment%20Handbook.pdf.
Scyphers, S. B., Powers, S.P., Heck, K.L., Byron, D., 2011, Oyster reefs as natural breakwaters mitigate shoreline loss and facilitate fisheries: PLOS One, v. 6, no. 8.
Marani, M., D'Alpaos, A., Lanzoni, S., and Santalucia, M., 2011, Understanding and predicting wave erosion of marsh edges: Geophysical Research Letters, v. 38, no. 21.
Taylor, J., and Bushek, D., 2008, Intertidal oyster reefs can persist and function in a temperate North American Atlantic estuary: Marine Ecology Progress Series, v. 361, p. 301-306.
Arcadis, Tech., S. I. o., TNC, Parks, N., Architects, M. N. L., and Landscape, S., 2014, Coastal Green Infrastructure Research Plan for New York City.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
TNC. 2013. Green Infrastructure Case Studies. https://www.nature.org/about-us/working-with-companies/case-studies-for-green-infrastructure.pdf.
TNC. 2018. “Gandy’s Beach Living Shoreline Project | The Places We Protect. the Humble Power of Oysters and Coconuts.” Accessed April 24. https://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/newjersey/placesweprotect/gandys-beach-living-shoreline-project-1.xml.

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ADDITIONAL BENEFITS

Photo credit: Flicker/UNC IMS

Livelihoods
Fisheries
Water quality
Biodiversity

Aside from shoreline stabilization and coastal defense, oyster reefs provide many ecosystem services including water filtration, food and habitat for many animals (e.g., fish, crabs, birds), and fisheries. For example:

Water quality. Artificial oyster reefs are already commonly used to reduce water pollution (e.g., nitrogen) via the oysters’ natural filtering abilities, thereby reducing dead zones and algal bloom. Oysters are filter feeders which strain microalgae and possibly dissolved organic matter from the water over their gills to feed. Additionally, they bioaccumulate some potential toxins and pollutants found in the water, and have been used to assess the environmental health of some areas. A single oyster may filter as much as 15 liters of water per hour, up to 1500 times its body volume.
Biodiversity. Many species, including commercially important fish, are dependent on oyster reefs at some point in their life cycle. Oyster reefs provide protective habitat for seagrasses, marshlands, and valuable habitat for fish, blue crabs and other marine animals.
Food supply, tourism, livelihoods. Reef functions such as fish habitat and water filtration can enhance tourism and recreation by improving adjacent water quality and sport fisheries. Fishery benefits alone from reef restoration in Mobile Alabama have a combined social return on investment (ROI) of 1.3 and 1.8 and a net present value of $1.17M and $3.23M, respectively, and produce over 3,100 kg of finfish and crab and 3,460 kg of oyster (meat) harvests per year.�

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References:

Hill, K. 2002. “Oyster Reef Habitats.” Smithsonian Marine Station. https://www.sms.si.edu/IRLSpec/Oyster_reef.htm.
Beck, Michael W., Robert D. Brumbaugh, Laura Airoldi, Alvar Carranza, Loren D. Coen, Christine Crawford, Omar Defeo, et al. 2011. “Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management.” BioScience 61 (2): 107–116. doi:10.1525/bio.2011.61.2.5.
TNC. 2013. Green Infrastructure Case Studies. https://www.nature.org/about-us/working-with-companies/case-studies-for-green-infrastructure.pdf.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Image: https://www.flickr.com/photos/uncims/14461319572/in/photolist-8NLAzV-pcmT4d-dW8M46-o2U3u5-5czuWD-fQeVp2-f6ELi2-dWerRq-aztAFK-oHWmcn-KdAryd-8QuPaV-dcJGLs-5PzEnq-o9fW2K-eC4gjL-azth3T-AJmvAa-2Ljnj-8NLB32-azvVwC-bSRBXP-8NPFvA-f6ELeF-aPntta-pZyBRr-qgNBbP-azvWn9-aPmEpM-nR9gYs-azweKu-prPxnY-B7Ee5w-aztghX-8NPFZh-23jJQ59-aPmUSp-bJC3tD-dWepDQ-4M5J5c-pkdQLi-dPgeC8-AJmrck-9dN3iH-aPnsWR-azvVRY-gFkZt9-naQLQM-SkVApN-f6FbK8

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CONSIDERATIONS FOR USING OYSTER REEFS AS COASTAL DEFENSE

Photo credit: Flickr/USACE NY

Effectively manage and protect existing reefs
Integrate reef restoration planning with other risk reduction strategies
Understand local site context for best site selection and restoration design
Incorporate valuation results into coastal planning and management decisions

Oysters reach sexual maturity in 1 year

When considering oyster reefs for disaster risk management objectives, there are a number of things to consider:

Reef longevity. Rates of oyster reef growth have been found comparable to rate of rising sea level, with intertidal oyster-reefs exhibiting the capacity for accelerated rates of accretion ahead of sea level rise. This has implications for the consideration of oyster reef restoration projects as tools for flooding and erosion mitigation.
Evaluate the physical habitat for site selection. Not all oyster reef restoration strategies work equally well across sites, and site selection is critical. Local hydrographic patterns as well as historical data on reef presence and success should be considered in selecting a site. Practitioners must consider tidal, hydrographic/current conditions, depth, bottom condition, and substrate type in development of restoration strategies.
Evaluate existing natural populations. As part of site selection, assess the area’s history of natural oyster population success (whether the site has ever supported a self-sustaining oyster population). Non-native shellfish can be introduced in areas where native species are declining, however incidence of disease is associated with transfers of nonnative oysters for aquaculture from ballast waters.
Integrated planning. Understand the interaction of reefs with neighboring ecosystems and other built structures or risk reduction measures. For example, if dikes are relied upon in the estuary, they can divert freshwater into oyster reef communities, significantly reducing salinity levels potentially making the environment unfavorable for reef growth.

Oysters are sexually mature by 1 year, and grow by approximately 30mm/year. A single female oyster produces 10-100 million eggs annually and a single male oyster produces about a billion sperm annually. The reef structure grows over time vertically and horizontally as younger animals settle onto the clean, fresh substrate created by older or dead oysters below.

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References:

Rodriguez, Antonio B., F. Joel Fodrie, Justin T. Ridge, Niels L. Lindquist, Ethan J. Theuerkauf, Sara E. Coleman, Jonathan H. Grabowski, et al. 2014. “Oyster Reefs Can Outpace Sea-Level Rise.” Nature Climate Change 4 (6): 493–497. doi:10.1038/nclimate2216.
Ridge, Justin T., Antonio B. Rodriguez, F. Joel Fodrie, Niels L. Lindquist, Michelle C. Brodeur, Sara E. Coleman, Jonathan H. Grabowski, and Ethan J. Theuerkauf. 2015. “Maximizing Oyster-Reef Growth Supports Green Infrastructure with Accelerating Sea-Level Rise.” Scientific Reports 5. doi:10.1038/srep14785
Baggett, L.P., S.P. Powers, R. Brumbaugh, L.D. Coen, B. DeAngelis, J. Greene, B. Hancock, and S. Morlock. 2014. Oyster Habitat Restoration Monitoring and Assessment Handbook. Arlington, VA, USA: The Nature Conservancy. https://www.conservationgateway.org/ConservationPractices/Marine/Documents/Oyster%20Habitat%20Restoration%20Monitoring%20and%20Assessment%20Handbook.pdf.
Beck, Michael W., Robert D. Brumbaugh, Laura Airoldi, Alvar Carranza, Loren D. Coen, Christine Crawford, Omar Defeo, et al. 2011. “Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management.” BioScience 61 (2): 107–116. doi:10.1525/bio.2011.61.2.5.
Virginia’s Oyster Reef Teaching Experience. n.d. Oyster Primer. Accessed April 29. http://www.vims.edu/research/units/centerspartners/map/education/resources/docs/OysterPrimer.pdf.
Image: https://www.flickr.com/photos/newyorkdistrict-usace/5058195060

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WHAT DO OYSTER REEFS COST?

Photo: Sarah Hall-Kirchner / Macdill Airforce Base

Source: Bayraktarove et al. 2015

Median oyster reef restoration cost estimate value is ~US$66,900/hectare

Costs of reef restoration measures have been found to be significantly less expensive than building tropical breakwaters

The cost of oyster reef restoration projects are cheaper than gray alternatives in initial costs. For example, the cost of constructing a tropical breakwater per linear foot is estimated to be US$5,000-10,000, whereas the cost of reef restoration is US$.23k - .24k/linear foot.
Median oyster reef restoration cost estimate value is US$66,821/hectare, according to Bayraktarove et al. 2015. Restoration cost is represented at US$ 2010/ha.
For coral reefs, seagrass, saltmarshes, and oyster reefs, only small‐scale restoration efforts of <1 ha have been documented.
Oyster reef restoration in Mobile, Alabama, discussed in the next slide, has costs estimated up to $625,000 per kilometer, or US$1 million per mile.

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References:

Bayraktarov Elisa, Saunders Megan I., Abdullah Sabah, Mills Morena, Beher Jutta, Possingham Hugh P., Mumby Peter J., and Lovelock Catherine E. 2015. “The Cost and Feasibility of Marine Coastal Restoration.” Ecological Applications 26 (4): 1055–1074. doi:10.1890/15-1077.
Gregalis, K. C., Powers, S. P., and JR, K. L. H., 2008, Restoration of Oyster Reefs along a Bio-physical Gradient in Mobile Bay, Alabama: Journal of Shellfish Research, v. 27, no. 5, p. 1163-1169.
TNC. 2013. Green Infrastructure Case Studies. https://www.nature.org/about-us/working-with-companies/case-studies-for-green-infrastructure.pdf.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund.
Image: http://www.macdill.af.mil/News/Article-Display/Article/765237/building-up-macdills-oceanic-ecosystem/

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DISASTER RISK MANAGEMENT WITH OYSTER REEF RESTORATION IN THE GULF OF MEXICO

Photo: Florida Sea Grant / Flickr

5.9 kilometers of restored oyster reefs in Mobile Bay, Alabama has:

Reduced wave height and energy: the average and top 10% of waves by 53-91% and 76-99%, respectively
Produced marine food supply: 3,100kg of finfish, crab and 3,460 kg of oyster meat/yr
Purified water: removing 1,888 kg of nitrogen/yr from surrounding nearshore waters

Project locations in Mobile Bay, �Gulf of Mexico.

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4. SANDY BEACHES AND VEGETATED DUNES

Photo: W & J / Flickr

Source: Schwartz 2006

Sandy beaches and dunes occur at all latitudes, covering ~34-40% of ice-free coastline

Approaches for implementation include:

Beach nourishment or replenishment through artificial replacement of sand to grow shoreline
Replenishing and protecting integrity of existing sand dunes
Constructing new sand dunes

Beaches occur where there is sufficient sediment for wave deposition above water level. Sandy beaches and dunes occur at all latitudes, on around 34-40% of the ice-free coastline.
This section covers beach nourishment and sand dunes, including with vegetation, as methods for risk reduction.
Beach nourishment or replenishment is the artificial placement of sand, or other sediment like pebbles, on an eroded shore to maintain the amount of sand present in the foundation of the coast. This compensates for natural erosion.

Sand for redistribution is mined or extracted from another location offshore, or imported, and placed on the destination beach or foreshore. It is then naturally distributed by wind, waves and currents in the beach system.

Sand dunes are ridges of sand either constructed or naturally created by wind along the coastline. Dunes that are vegetated provide greater resistance to erosion, and more durability.

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References:

US Army Corps of Engineers. 2013. Coastal Risk Reduction and Resilience. http://www.swg.usace.army.mil/Portals/26/docs/PAO/Coastal.pdf.
Schwartz, Maurice. 2006. Encyclopedia of Coastal Science. Springer Science & Business Media.
Barbier Edward B., Hacker Sally D., Kennedy Chris, Koch Evamaria W., Stier Adrian C., and Silliman Brian R. 2011. “The Value of Estuarine and Coastal Ecosystem Services.” Ecological Monographs 81 (2): 169–193. doi:10.1890/10-1510.1.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Image: https://www.flickr.com/photos/mentalwanderings/31915742233/in/photolist-QChweP-RoFZNJ-65JCfs-Yf5jdf-XDVC3W-UHcSw7-5xvCDF-Ymcag1-ShxjdX-T2Ukms-fbce1j-ddWmK1-oEkR65-22aTf2E-cjiV2N-22FT1rW-WCz3XS-dMvWU6-dNoDfa-T6ar4B-Vx2phe-dKh7C5-TwUStQ-SuipUo-CznErD-QsXqV5-ekchr1-jkJDm7-T1AFuf-TSupbW-VAjZ8s-jd7g8y-Rdz8zc-ek6yCF-evcqt1-TWg75C-VfpJkh-So2wfP-6vk8j5-WBpGwW-RUJXb9-YXzT7g-VLveV5-24VA8vD-6r8M2h-XpUToW-6RbqkR-6xpPLq-YAu8oe-e2RMwC

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RISK REDUCTION BENEFITS

Photo credit: Dave Gingrich / Flickr

Graphic credit: Ward 2015

Beaches:

Attenuate waves
Provide shoreline stability and erosion reduction

Deep water storm waves

Vegetated dunes:

Reduce wind speed
Act as barriers against waves, currents, storm surges

Beaches and sand dunes help to reduce shoreline erosion and prevent flooding by reducing the risk of storm surge-related wave attacks and flooding on barrier islands and the mainland. Wide beaches and high dunes are the most suitable for risk reduction.
Beaches provide benefits as the sloping nearshore bottom causes waves to break, dissipating wave energy over the surf zone. They break up offshore waves and attenuate wave energy; reduce storm surge induced flooding; protect shoreline stability through the prevention of new erosion inlets on the coastline; protect down drift of the beach through sand re-disbursement; and hinterland protection through dune reinforcement by redistributing beach sand to dunes.
Vegetated dunes perform more efficiently than non-vegetated dunes, ensuring stability, greater energy dissipation and resistance to erosion. They provide benefits like decreased wind speeds; wave energy attenuation as barriers against storm surges, currents and waves. The absorb water impact, preventing or delaying flooding of inland areas and damages to inland structures. As part of the beach system they can also transfer sand/sediment back to the beach.

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References:

NRC 2014, Reducing Coastal Risk on the East and Gulf Coasts, Washington, DC, The National Academies Press.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
US Army Corps of Engineers. 2013. Coastal Risk Reduction and Resilience. http://www.swg.usace.army.mil/Portals/26/docs/PAO/Coastal.pdf.
Ward, J. 2015. “Engineering the Recovery from Hurricane Sandy.” Www.Army.Mil. https://www.army.mil/article/143684/engineering_the_recovery_from_hurricane_sandy.
Image: https://www.flickr.com/photos/ndanger/368776554/in/photolist-yA5qs-bWjQ8v-ejWtW4-eboxgp-bvGswM-pt2y8C-8ED6zN-qjFv2R-pPEELa-a8hfNH-5McNZH-5dUn1m-bYNjMS-4khAKL-qKqCQp-8hbCGk-87JgU5-93JLsP-rAcH5b-5qfbw1-mV9FC-daRs3p-pcsXYF-h67LU-9jhWKo-4etW9j-pqUwTx-2CAZ9V-3KNmQz-8CfTsy-nEunET-fHGdHQ-HQTbS-anYFU8-9WGXYc-4wvvNf-9EFspY-PB4a-dkvQUa-4sehrx-6x7MN7-mPmCvB-8WHvBg-j3e7Zo-fmZsGn-kcjpee-awTWq1-ee6YDR-Jeqk8k-95bT7u

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ADDITIONAL BENEFITS

Tourism and recreation
Groundwater storage and supply
Biodiversity and wildlife

Photo credit: Flickr/Ian

Beyond their risk reduction benefits, sandy beaches and vegetated dunes also contribute to the attractiveness of coastlines for tourism and recreation, and their aesthetic and recreational values can contribute to increased property values for coastal area residents.

For example, coastal states in the United States receive about 85% of tourist-related revenues in the U.S. In 2007, U.S. beaches were estimated to yield an estimated $322 billion annually to the national economy.

Vegetated dunes and beaches also provide crucial habitat and food for birds and small mammals, and protection for other animals like sea turtles and crabs.
Dunes are not only nature reserves, but they also supply drinking water to coastal regions. For example, the Meijendel dunes are the largest coherent dune landscape in the southern Netherlands and provide drinking water to millions of people, with more than 3.5 million people living within 25 kilometers of the area.

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References:

Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Houston, James R. 2008. “The Economic Value of Beaches – A 2008 Update.” Shore & Beach 76. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.496.312&rep=rep1&type=pdf.
Durkin, C. 2010. Coastal Dune Management at Selected Sites in the Netherlands: South Holland and Zeeland. http://coast.hope.ac.uk/media/liverpoolhope/contentassets/documents/coast/media,25636,en.pdf.
Barbier Edward B., Hacker Sally D., Kennedy Chris, Koch Evamaria W., Stier Adrian C., and Silliman Brian R. 2011. “The Value of Estuarine and Coastal Ecosystem Services.” Ecological Monographs 81 (2): 169–193. doi:10.1890/10-1510.1.
Image: https://www.flickr.com/photos/ian-s/7023979133

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CONSIDERATIONS FOR USING SAND NOURISHMENT AND VEGETATED DUNES AS COASTAL DEFENSE

Photo: Patrick Bloodgood

Regional distinctions and site characteristics
Integrity of artificial dunes vs. preserving and reinforcing existing dunes
Different design vulnerabilities under same storm and wave characteristics
Incorporate valuation results into coastal planning and management decisions

Nourishment can be required every 3-5 years

Coastlines are vibrant and lively systems. When considering sand nourishment or vegetated dunes for coastal defense, design considerations include:

Regional distinctions and characteristics of the site. This includes the beach/dune slope, width, sediment grain size, natural dune vegetation and project / risk timeline. For example:

Timeline: if the area is an erosion hot spot, the lifetime of a beach nourishment project is often short and may need to be re-nourished frequently.
Grain size: coarser grains create steeper profile and wider beaches and is more stable in terms of longshore loss.
Vegetation: which species naturally thrive, and why (e.g., deep roots that sustain high-velocity flows).

The scale and location of nourishment operations. These will be affected by the risk objectives and site characteristics. High dunes are generally the most suitable, but dunes built in areas that would not be naturally sustainable are less likely to survive, and unnaturally high dunes can also fail. Location prospects include:

Beach nourishment: sand is spread over the beach where erosion is occurring to compensate shore erosion and restore the recreational value of the beach. Wind will then distribute the sand onshore and in the dunes.
Backshore nourishment: sand is stockpiled on the backshore (part of the beach above the foreshore, which is only exposed to waves under extreme events) to strengthen the dunes against erosion and breaching in case of storm. The sand may deplete greatly during storms.
Shoreface nourishment (the area between the mean low water mark and the fair weather wave base). The reduction of wave energy leads to enhanced accumulation at the beach. This can be combined with beach nourishment to strengthen the entire coastal profile.

Integrity of artificial dunes. Artificial dunes do not necessarily respond the same way to storm processes as natural dunes. Even when indigenous species are planted on artificial dunes, the roots may remain shallow, since plants did not grow while the dunes aggraded. Consequently, artificial dunes can be less resistant to wave attack and erosion than natural dunes, and as a result they may erode more rapidly.
Understanding there are different susceptibilities for designs under same storm and wave characteristics. For example, a new project may suffer a severe storm immediately upon completion, resulting in massive fill losses, or the beach fill may serve for many years without ever being exposed to design storm conditions. Or, for example, high vegetated dunes can preclude the penetration of storm surge, and simultaneously divert the high-velocity flow into adjacent low-lying areas that become washover conduits.
Once begun, regular nourishment operations can be required on intervals from every 3-5 years, depending naturally on coastal conditions including major erosion events like hurricanes or tsunamis. In the Netherlands, for example, where regular sand nourishment plays an active role in coastal protection, shorelines and beaches need sand replenishment every 4-5 years.

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References:

NRC 2014, Reducing Coastal Risk on the East and Gulf Coasts, Washington, DC, The National Academies Press.
Morton, R. A., 2002, Factors Controlling Storm Impacts on Coastal Barriers and Beaches: A Preliminary Basis for near Real-Time Forecasting: Journal of Coastal Research, v. 18, no. 3, p. 486-501.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Image: https://media.defense.gov/2017/Mar/01/2001705368/-1/-1/0/170227-A-OI229-013.JPG

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WHAT DO BEACHES AND DUNES COST?

Cost of beach nourishment has been found between US$2,000-5,000/linear ft. and vegetated dunes US$.03k-5,000/linear ft.

Photo: draconianimages / pixabay

Source: Cunniff and Schwartz 2015; NRDA 2012

Cost of constructing a tropical breakwater per linear foot is estimated to be US$5,000-10,000

Combined cost estimates for dune planting and beach nourishment operations have reached US$16 million/km. Median estimates for dune planting have reached $98,000 per kilometer, and $6.6 million per kilometer for beach nourishment. Cost estimates for both measures combined have reached $16 million per kilometer.
The cost of nourishment projects are comparable to gray alternatives in initial costs. For example, the cost of constructing a tropical breakwater per linear foot is estimated to be US$5,000-10,000, whereas the cost of nourishment is US$2,000-5,000/linear foot. Vegetated dune creation has ranged from US$.03k-5,000/linear foot.

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References:

Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
NRDA-Trustees, 2012, Florida (Pensacola Beach) Dune Restoration Project, Volume Phase I Early Restoration Plan.
Image: https://pixabay.com/en/beach-view-sand-bar-sea-tourist-2352667/

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DISASTER RISK MANAGEMENT WITH MEGA-SAND NOURISHMENT IN THE NETHERLANDS

Photo: Flickr/Anthony Tong Lee

Source: Rijkswaterstaat 2013; Tall et al. 2016

2011

2014

21.5 million m³ of sand deposited to build resilient shoreline as first line of defense
Cost: €70 million for nourishment operation
Expected outcome: fewer nourishment operations required over a 20-year time horizon, dune reinforcement, and less disturbance of coastal ecosystem

Sand nourishment projects have generally been used since 1920s in the United States and since the 1950s in Europe, but large-volume sand nourishment projects, or “mega-nourishments,” are a novel approach.
Sand nourishment and dunes are first lines of coastal defense in the Netherlands, where shorelines and beaches need sand replenishment every 4-5 years. Off the Defland Coast of the South Holland Province, an experimental mega nourishment project, known as the Sand Motor, is underway.
It was created in 2011 by the deposition of 21.5 million m³ of sand dredged from offshore deposits onto the foreshore in a peninsula designed in the shape of a hook with a lagoon. The first of its kind mega artificial sand nourishment project has been constructed to pilot whether its innovative sand nourishment design can maintain the coastal equilibrium of the Defland Coast, building primary defense dunes and requiring fewer regular nourishment operations on that coastline over a 20-year time horizon.
The project is estimated to benefit ecological and recreational uses, and protect the shoreline – but it has not yet been evaluated. Since original deposit, the sand has been distributed by natural wind, waves and currents. Evaluation from the first 4 years shows that dunes have grown slower than expected, but that the shoreline has been expanded both to the north and south of the original Sand Motor design.
The project area still contains an additional volume of sand equivalent to 95 percent of the volume deposited at construction. Tourism and biodiversity are also on the rise.

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References:

Bontje, Lotte E., and Jill H. Slinger. 2017. “A Narrative Method for Learning from Innovative Coastal Projects – Biographies of the Sand Engine.” Ocean & Coastal Management 142 (June): 186–197. doi:10.1016/j.ocecoaman.2017.03.008.
Rijkswaterstaat. 2013. “Sand Motor Fact Sheet: Pilot Project for Natural Coastal Protection.” http://www.dezandmotor.nl/uploads/2015/09/factsheet-zandmotor-delflandse-kust-eng-lr.pdf.
Taal, M.D., M.A.M. Loffler, C.T.M. Vertegaal, J.W.M. Wijsman, L. Van der Valk, and P.K. Tonnon. 2016. Development of the Sand Motor: Concise Report Describing the First Four Years of the Monitoring and Evaluation Programme (MEP). Deltares. http://www.dezandmotor.nl/uploads/2016/09/monitoring-and-evaluation-report-sand-motor-eng.pdf.
UNESCO/IOC. 2012. “Guide on Adaptation Options in Coastal Areas for Decision-Makers.” http://unesdoc.unesco.org/images/0021/002166/216603E.pdf.
Image: https://www.flickr.com/photos/atonglee/15963966391/in/photolist-qjFv2R-a8hfNH-5McNZH-eboxgp-5dUn1m-qixte7-pPEELa-bYNjMS-cqWu5u-8ED6zN-4khAKL-e2RMwC-qKqCQp-8hbCGk-rAcH5b-5qfbw1-mV9FC-bh1RRD-h67LU-jkJDm7-daRs3p-4etW9j-pqUwTx-87JgU5-pcsXYF-2CAZ9V-9jhWKo-93JLsP-pdeJZA-fHGdHQ-nEunET-8CfTsy-HQTbS-6WFdsN-nZ1K81-j3e7Zo-4wvvNf-fmZsGn-iHdjWs-ee6YDR-95bT7u-3KNmQz-Jeqk8k-fWpw5R-oQHbcX-pbjM9t-9WGXYc-7yvody-6kmqJv-anYFU8

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5. COASTAL WETLANDS

Photo credit: Flickr/USFWS

Salt marshes are located in the intertidal zone of sheltered marine and estuarine coastlines, commonly found at temperate and high latitudes, and comprise salt-tolerant plants like herbs, grasses and shrubs

Approaches for implementation include:

Conserving existing marshes
Rehabilitating a degraded marsh
Re-establishing a destroyed marsh

Two general categories of wetlands are typically recognized: coastal or tidal wetlands and inland or non-tidal wetlands. Tidal wetlands, and specifically saltmarshes—not mangrove swamps or forests—are the wetland ecosystem focused on in this section.
Salt marshes are ecosystems located in the intertidal zone of sheltered marine and estuarine coastlines. These ecosystems comprise brackish, shallow water with salt-tolerant plants such as herbs, grasses and shrubs, and are commonly found at temperate and high latitudes.
Wetland restoration rehabilitates a degraded wetland or reestablishes a wetland that has been destroyed. Restoration takes place on land that has been, or still is, a wetland. Coastal wetlands can often be restored by reducing pollution, replanting lost vegetation (either transplants from donor sites/labs or seed broadcasts) and/or repairing the natural flow of water.

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References:

Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes. Biodiversity Data Journal 5: e11764.
US EPA, OW. 2015. “What Is a Wetland?” Overviews and Factsheets. US EPA. https://www.epa.gov/wetlands/what-wetland.
Image: https://www.flickr.com/photos/usfwsnortheast/5187274473

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GLOBAL DISTRIBUTION OF COASTAL WETLANDS

Source: Mcowen et al. 2017

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RISK REDUCTION BENEFITS

Graphic Source: Ferdana et al. 2014

undamaged

damaged

Sediment stabilization facilitated by root systems
Wave energy dissipation and attenuation

Salt marshes are estimated to reduce non-storm wave heights by an avg. of 72% and wave energy by up to 60%

Salt marshes can provide coastal storm protection services through wave attenuation and sediment stabilization. For example:

Wave attenuation. The dense vegetation and shallow water depths within wetlands can slow the advance of storm surge and slightly reduce the surge landward of the wetland or slow its arrival time. Wetlands also dissipate wave energy, potentially reducing the amount of destructive wave energy propagating on top of the surge. However, it is possible the storm surge propagation in one area translates the movement of water toward another location, potentially causing a local storm surge increase elsewhere. Attenuation for wind waves is greater during low energy events than for storm surge events. On average, salt marshes reduce wave heights in their sheltered environments by 72% and non-storm wave energy by up to 60%.
Sediment stabilization. Coastal wetland vegetation modifies shorelines by accumulating soil and peat to increase shoreline integrity, providing lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. Vertical accretion rates are roughly 5mm/year, and can keep up with sea level rise so long as it does not outpace the rate of accretion.

In the United States, coastal wetlands provide US$23.2 billion/year in storm protection services. In 2012, wetlands avoided $625 Million in direct flood damages during Hurricane Sandy.
On average, coastal habitats reduce wave heights between 35% and 71%. Coral reefs reduce wave heights by 70% (95% CI: 54–81%), salt-marshes by 72% (95%CI: 62–79%), mangroves by 31% (95% CI: 25–37%) and seagrass/kelp beds by 36% (95% CI: 25–45%).

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References:

US Army Corps of Engineers. 2013. Coastal Risk Reduction and Resilience. http://www.swg.usace.army.mil/Portals/26/docs/PAO/Coastal.pdf.
Gedan, Keryn B., Matthew L. Kirwan, Eric Wolanski, Edward B. Barbier, and Brian R. Silliman. 2011. “The Present and Future Role of Coastal Wetland Vegetation in Protecting Shorelines: Answering Recent Challenges to the Paradigm.” Climatic Change 106 (1): 7–29. doi:10.1007/s10584-010-0003-7.
Sutton-Grier, A.E., K. Wowk, and H. Bamford. 2015. “Future of Our Coasts: The Potential for Natural and Hybrid Infrastructure to Enhance the Resilience of Our Coastal Communities, Economies and Ecosystems.” Environmental Science & Policy 51: 137–148.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.
Holmquist, J. R., L. N. Brown, and G. M. MacDonald. 2015. “Linking Historic Wetland Soil Accretion and Sea-Level Rise Data with Landcover Change in the US.” AGU Fall Meeting Abstracts 53: GC53A-1190.
Narayan, Siddharth, Michael W. Beck, Paul Wilson, Christopher J. Thomas, Alexandra Guerrero, Christine C. Shepard, Borja G. Reguero, Guillermo Franco, Jane Carter Ingram, and Dania Trespalacios. 2017. “The Value of Coastal Wetlands for Flood Damage Reduction in the Northeastern USA.” Scientific Reports 7 (1): 9463. doi:10.1038/s41598-017-09269-z.
Ferdana, Z., TNC, G. Raber, and U. So. Miss. 2014. “GIS Helps Integrate Coastal Hazard Risk and Sea Level Rise.” ArcNews. http://www.esri.com/esri-news/arcnews/summer14articles/gis-helps-integrate-coastal-hazard-risk-and-sea-level-rise.

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ADDITIONAL BENEFITS

Photo credit: Flickr/ Bureau of Land Management

Livelihoods
Water quality
Carbon sequestration
Biodiversity and habitat

Aside from coastal defense, wetlands also provide a range of additional benefits and ecosystem services, including:

Biodiversity and habitats. Saltmarshes are of ecological importance as they underpin the estuarine food web. Saltmarshes serve as nesting, nursery and feeding grounds for numerous species of birds, fish, mollusks and crustaceans, including commercially important fish species like herring. The shallow water and vegetation provides hiding places and abundant food for juvenile fish and various invertebrate species. Larger predators cannot enter these areas, making them a temporary safe haven while the fish have a chance to grow. Saltmarshes are also a particularly important breeding, foraging, overwintering and migration stop off points for many waterfowl species.
Nutrient cycling, water filtration, immobilization of pollutants and carbon sequestration. Saltmarshes are one of three key coastal carbon habitats, recognized for their ability to store carbon within above- and below-ground biomass and sediments. With an average annual carbon sequestration rate of 6 to 8 tonnes of CO2 equivalent per hectare, saltmarshes sequester carbon at a rate two to four times greater than that recorded for mature tropical forests. They also protect water quality by filtering terrestrial and river runoff and metabolizing excess nutrients, resulting in sedimentation, increased nutrient uptake by grasses, and better water quality for associated ecosystems like seagrass beds. Because of wetlands, wastewater treatment in southern Louisiana saves around US$1,940- US$37,050/ha in conventional treatment costs.
Livelihoods. Wetlands produce shrimp, oysters, clams and fish. For example, ~75% of U.S. commercial fish use salt marshes as spawning ground and nursery, and salt marshes in the Gulf of Mexico account for 66% of U.S. shrimp production.

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References:

Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes. Biodiversity Data Journal 5: e11764.
Barbier Edward B., Hacker Sally D., Kennedy Chris, Koch Evamaria W., Stier Adrian C., and Silliman Brian R. 2011. “The Value of Estuarine and Coastal Ecosystem Services.” Ecological Monographs 81 (2): 169–193. doi:10.1890/10-1510.1.
Image: https://www.flickr.com/photos/blmoregon/15410101260/

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CONSIDERATIONS FOR USING WETLANDS AS COASTAL DEFENSE

Photo credit: Flickr/ Alaska USFWS

Adaptive nature can keep pace with sea level rise and recover from weather events
Integrated coastal management strategies
Focus on local species with preferable vegetation characteristics
Incorporate valuation results into coastal planning and management decisions

Considerations for using salt marshes for coastal risk reduction include:

Adaptive abilities. With sufficient sediment and nutrient load, wetlands can self-adapt to gradual hazards, such as sea-level rise, and can self-recover from moderate damage due to, for example, storm events or ice cover. Salt marshes may also be able to maintain the coastline relative to sea level rise by accreting sediment at a level comparable to or even higher than sea level rise providing a further reduction in vulnerability to hazards and climate change.
Integrated coastal management strategies. Salt marshes have lost 25-50% of their global historical coverage, and the current rate of loss is 1-2%/year. Over longer time scales, projections of sea level rise suggest that wetlands will require management and intervention to preserve their ability to reduce risks and provide ecosystem services. Water logged marshes may not provide same wave attenuation benefits, and could potentially increase wave energy. Even though salt marshes are adaptive and have the capacity to migrate landward to survive sea level rise, their ability to do so and continue to accrete shoreline can be prohibited by physical obstacles that not only prevent them from adjusting, but affect the tidal flows and general protective health of the system.
Target interventions toward local species with preferable vegetation characteristics. This includes factors associated with wave attenuation such as marsh width and vegetation height, stem stiffness, and stand density. Stiffer, short-stemmed vegetation is preferred in denser communities, as near-emergent vegetation is most effective for wave reduction.

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References:

Hale, L. Z., Meliane, I., Davidson, S., Sandwith, T., Beck, M., Hoekstra, J., Spalding, M., Murawski, S., Cyr, N., Osgood, K., Hatziolos, M., Eijk, P. V., Davidson, N., Eichbaum, W., Dreus, C., Obura, D., Tamelander, J., Herr, D., McClennen, C., and Marshall, P., 2009, Ecosystem-based Adaptation in Marine and Coastal Ecosystems: Renewable Resources Journal, v. 25, no. 4, p. 21-28.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes. Biodiversity Data Journal 5: e11764.
Arcadis, Tech., S. I. o., TNC, Parks, N., Architects, M. N. L., and Landscape, S., 2014, Coastal Green Infrastructure Research Plan for New York City.
Image: https://www.flickr.com/photos/usfws_alaska/6728425873/in/photolist-bfyWAD-8aPJL6-dQBioc-6Pd2Yg-p735Dp-ofgyhg-8rX5hD-9Us1jb-9W93zR-9UsaHL-oBVboC-9JMXaY-71XzB4-CokVnR-9UsC8W-9UsKgA-21Z624j-9RjzU7-4jqRb7-9TRQUa-8kWVzL-fjq7WS-ajwTqV-pVqAb6-naoohT-YbYmEd-V4mzAR-6Pd2Ug-ZiA4Cv-9W98fK-YbYh8C-Teu12r-fgyXjx-pDe5L8-6PhbLW-XSzjgy-biaeiM-pDaEUt-6Phd3q-Yg7N3x-RC9G8b-ZWxQ8A-6Pd4d2-9W965K-dPxMbZ-6PhcF5-21Z5Y89-EHHjDE-pD753d-6PhaDo

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WHAT DO COASTAL WETLANDS COST?

Photo credit: Flickr/ Chesapeake Bay Program

Source: Narayan et al. 2016; Bayraktarove et al. 2015

Wetland restoration can be 2-5x cheaper than submerged breakwaters for equivalent wave heights up to half a meter

Median salt marsh restoration cost estimate value is ~USS$67,100/hectare

The cost range of salt marsh restoration projects is estimated to be between US$.01-33/m². Compared to the costs of submerged breakwaters, this can be 2-5 times cheaper for equivalent wave heights up to half a meter.
Median salt marsh restoration cost estimate value is US$67,128/hectare, according to Bayraktarove et al. 2015. Restoration cost is represented at US$ 2010/ha.
For coral reefs, seagrass, saltmarshes, and oyster reefs, only small‐scale restoration efforts of <1 ha have been documented. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, is highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%).

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References:

Bayraktarov Elisa, Saunders Megan I., Abdullah Sabah, Mills Morena, Beher Jutta, Possingham Hugh P., Mumby Peter J., and Lovelock Catherine E. 2015. “The Cost and Feasibility of Marine Coastal Restoration.” Ecological Applications 26 (4): 1055–1074. doi:10.1890/15-1077.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.
Image: https://www.flickr.com/photos/29388462@N06/

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DISASTER RISK MANAGEMENT WITH SALT MARSH RESTORATION IN NARRAGANSETT BAY

Photos: Save the Bay Project (1996-2002)

200 acres under restoration
Expected outcome: Improving tidal flow, water quality, and reinvigorating high and low marsh plants to restore ecosystem services and adaptive protective benefits

Since 1999, the Save the Bay project in Narragansett Bay, Rhode Island has worked with communities to restore nearly 200 acres of salt marsh. Many projects are still underway, but some have been completed and are deemed successful.
The projects work toward improving water flow in and out of the marsh, treatment of storm water and planting of vegetation buffers to improve water quality and planting of high and low marsh plants. Restricted water flow resulting from the nearby built structures and nutrient levels from terrestrial runoffs were creating favorable environments for invasive species, affecting the plant diversity and habitat value, as well as the habitat’s ability to migrate landward and sustain sea level rise.
The projects are additionally benefiting 63 fish species using the salt marshes as nurseries, as well as a host of egrets, herons, osprey and other migratory birds that frequent the habitat each year.

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References:

Save the Bay. 2008. “Salt Marsh Restoration Fact Sheet.” http://www.savebay.org/file/web-site-pdfs/Salt_Marsh_Fact_Sheet_FINAL.pdf

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6. SEAGRASS BEDS

Photo credit: Flickr/Dugong Seagrass

Seagrasses are dominant forms of shallow sub-tidal vegetation found across the world, from tropical to arctic latitudes

Approaches for implementation include:

Protecting existing seagrass beds
Enabling water quality and protective conditions for natural regeneration
Transplanting or broadcasting seeds from laboratories or plants from donor sites

Seagrasses are a unique group of flowering plants that grow in the shallow coastal waters of most continents. Seagrasses can form vast aggregations, or meadows and have evolved the ability to grow completely submerged by seawater in part thanks to their underwater pollination system. They are able to cope with saline water, and have rooting structures which allow them to withstand the movement of water.
Seagrasses grow in salty and brackish (semi-salty) waters around the world, typically along gently sloping, protected coastlines. Because they depend on light for photosynthesis, they are most commonly found in shallow depths where light levels are high, they colonize soft substrates such as mud, sand
They can be restored by encouraging natural recolonization in areas that have experienced improvements in surface water quality; transplanting of individual seagrasses taken from healthy donor beds; or seedlings reared under laboratory conditions. In some cases seeds can be planted or broadcast. Seeding can be used alone, or in concert with transplant techniques.

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References:

NRC 2014, Reducing Coastal Risk on the East and Gulf Coasts, Washington, DC, The National Academies Press.
UNEP-WCMC, Short FT (2017). Global distribution of seagrasses (version 5.0). Fourth update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. URL: http://data.unep-wcmc.org/datasets/7
Short, F., T. Carruthers, W. Dennison, and M. Waycott. 2007. “Global Seagrass Distribution and Diversity: A Bioregional Model.” Journal of Experimental Marine Biology and Ecology, The Biology and Ecology of Seagrasses, 350 (1): 3–20. doi:10.1016/j.jembe.2007.06.012.
Fonseca, M.S., W.J. Kenworthy, and G.W. Thayer. 1998. Guidelines for the conservation and restoration of seagrasses in the United States and adjacent waters. NOAA Coastal Ocean Program Decision Analysis Series No. 12. NOAA Coastal Ocean Office, Silver Spring, Maryland.
Image: https://www.flickr.com/photos/dugongproject/33181720970/in/photolist-Sy9ZBq-f7TTRL-oC61P-SWCJtc-RU3FjX-9ocL2f-RU3D4K-cv69Md-WxxxjV-T5qGuJ-6yYrTR-aN5izM-3k7mPq-RU3E8Z-nH67n1-V6qjyL-4nccBQ-3cwb1G-aCKxf8-fHu2Dg-RRtMsC-RU3DEz-7hzu4b-5N3BNF-ehAe9y-Xbq8B1-RtqC7E-LiGWXp-V4h6TL-LvD1k1-4MLdhh-RU3Cnp-atyXAG-7SXFn9-RU3FSk-W1Csfd-Gez1aR-RU3DZx-J1xbts-QuReTW-UZ9xV3-bWsVxt-TtmNA9-UfcZAu-XakFXp-cMpFEf-62xaTY-WPBd9R-2MHp1w-jf7BGA

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GLOBAL DISTRIBUTION OF SEAGRASS

Graphic source: UNEP 2017

Source: Short et al. 2007

Less than 60 species of seagrass exist, but species have ranges that can extend for thousands of kilometers of coastline

Seagrasses are broadly distributed in most of the world’s oceans and seas, including the Black and Caspian Seas. The global distribution of seagrasses extends up within the Arctic Circle, where they are present in northern Russia, Norway and Alaska. Seagrass has also been recorded as far south as New Zealand.
Strong wave action, nutrient concentration, ice scouring, depth and water turbidity are some of the limiting factors to the distribution of seagrasses.
Seagrasses have been disappearing at a rate of 110km²/yr since 1980, a rate of decline of 7% annually.

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References:

Short, F., T. Carruthers, W. Dennison, and M. Waycott. 2007. “Global Seagrass Distribution and Diversity: A Bioregional Model.” Journal of Experimental Marine Biology and Ecology, The Biology and Ecology of Seagrasses, 350 (1): 3–20. doi:10.1016/j.jembe.2007.06.012.
Waycott, Michelle, Carlos M. Duarte, Tim J. B. Carruthers, Robert J. Orth, William C. Dennison, Suzanne Olyarnik, Ainsley Calladine, et al. 2009. “Accelerating Loss of Seagrasses across the Globe Threatens Coastal Ecosystems.” Proceedings of the National Academy of Sciences 106 (30): 12377–12381. doi:10.1073/pnas.0905620106.
UNEP-WCMC, Short FT (2017). Global distribution of seagrasses (version 5.0). Fourth update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. URL: http://data.unep-wcmc.org/datasets/7

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RISK REDUCTION BENEFITS

Photo credit: Flickr/budak

Graphic credit: Guannel et al 2016

Wave attenuation
Shoreline stabilization through sediment retention and deposition

Seagrass

Seagrasses are estimated to reduce wave heights by an average of 36%

Seagrass modulate water flow and currents, contribute to wave attenuation and retain and stabilize sediments in shallow coastal areas. For example:

Seagrasses are estimated to reduce wave height by an average of 36%. Their attenuation effect is highest when plants occupy the entire water column such as with low tide. The dissipation of wave energy plays a role in reducing erosion of coastlines.
Seagrass habitats help stabilize the marine sediment and provide a framework for the accumulation of more sediment and other materials. Such sediment retention can lead to sediment accretion and reduced water turbidity.

Seagrass help mitigate erosive waves and stabilize shorelines, but their frictional forces are quickly reduced by higher water levels associated with storm surge or flooding during extreme storm events. Continued sea level rise could render the wave attenuation protective properties of seagrasses ineffective.
Together, live corals, seagrasses, and mangroves supply more protection services than any individual habitat or any combination of two habitats.
On average, coastal habitats reduce wave heights between 35% and 71%. Coral reefs reduce wave heights by 70% (95% CI: 54–81%), salt-marshes by 72% (95%CI: 62–79%), mangroves by 31% (95% CI: 25–37%) and seagrass/kelp beds by 36% (95% CI: 25–45%).

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References:

Short, Frederick, Beth Polidoro, Suzanne Livingstone, Kent E. Carpenter, Bandeira Salomao, Japar Sidik Bujang, Hilconida P. Calumpong, et al. 2011. “Extinction Risk Assessment of the World’s Seagrass Species.” Biological Conservation 144: 1961–1971. doi:10.1016/j.biocon.2011.04.010.
NRC 2014, Reducing Coastal Risk on the East and Gulf Coasts, Washington, DC, The National Academies Press.
Narayan, Siddharth, Michael W. Beck, Borja G. Reguero, Iñigo J. Losada, Bregje van Wesenbeeck, Nigel Pontee, James N. Sanchirico, Jane Carter Ingram, Glenn-Marie Lange, and Kelly A. Burks-Copes. 2016. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PLOS ONE 11 (5): e0154735. doi:10.1371/journal.pone.0154735.
Barbier Edward B., Hacker Sally D., Kennedy Chris, Koch Evamaria W., Stier Adrian C., and Silliman Brian R. 2011. “The Value of Estuarine and Coastal Ecosystem Services.” Ecological Monographs 81 (2): 169–193. doi:10.1890/10-1510.1.
Guannel, Greg, Katie Arkema, Peter Ruggiero, and Gregory Verutes. 2016. “The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience.” PLOS ONE 11 (7): e0158094. doi:10.1371/journal.pone.0158094.
Image: https://www.flickr.com/photos/wildsingapore/6197098412/in/photolist-arBKsm-UJag7x-bzVmqG-dLp3Bt-GYdCF-5MLSc3-8Etnxy-5MGBUc-7vCjZk-aaAq76-5ApRc8-8ssyXN-fjYsvF-6F1Zob-8EtnMJ-fHNemY-9hi4sG-8EqdDR-FhZRA-fkdAkb-abTb6H-8ssz8U-oKn45v-fHNeuC-arBK81-e8gifT-f5WzLZ-6BfMAa-kq6oV8-LYgi33-LYetir-LYgipq-dLuzm7-RzZ8Am-7cPr19-dQEgQ9-4LYR2s-SkwU9D-Dh1au-ftuDbw-7VEibv-Wsmx3K-7ZY9ZK-f5WzJx-26b4mBq-5tycY8-e68Tii-fHNfeq-6Ux2S-RRQSNH/

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ADDITIONAL BENEFITS

Photo: Jayhem / Flickr

Livelihoods
Fisheries
Water quality
Carbon sequestration
Biodiversity

Seagrass provide an estimated US$1.9 trillion/yr in the form of nutrient cycling

Beyond providing resilience to strong waves and erosion, seagrasses provide a number of ecosystem benefits valued at US$34,000 per hectare per year, including:

Fisheries. Seagrass are habitat for fish, scallops, shrimps and crabs and other species. For example, in the Bohol Marine Triangle, Philippines, annual net revenue from seagrass-associated species ranges from roughly US$12-200 per hectare. In Australia, the seagrass associated fish, shrimp and crab yield is valued at US$1,400 per hectare.
Water quality and nutrient cycling. The benefits provided by a healthy seagrass meadow extends beyond the local area, through exporting key nutrients (e.g. nitrogen and phosphate) and organic carbon to other parts of the oceans, including some to the deep-sea where they provide a critical supply of organic matter in an extremely food-limited environment. Seagrass provide an estimated US$1.9 trillion per year in the form of nutrient cycling.
Carbon sequestration. Much of the excess organic carbon produced is buried within the seagrass sediments, making seagrass habitat an important carbon sink. Seagrass occupy less than .2% of the area of the world’s ocean, but are estimated to bury 27.4Tg of carbon per year, equivalent to roughly 10% of the yearly estimated organic carbon burial in the oceans.
Biodiversity and food web structure of the local environment. 70% of all marine life depend on seagrass; they cover large areas and provide a complex structure which allow them to support thousands of other species, including microalgae, algae, small invertebrates to sharks, mollusks and crustaceans. Seagrass enhance coral reef productivity, provide essential habitats (e.g. spawning, nursery, refuge and foraging areas) for commercially and recreationally important fish species, and provide food for a range of large herbivores like sea turtles and manatees.

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References:

UNEP-WCMC, Short FT (2017). Global distribution of seagrasses (version 5.0). Fourth update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. URL: http://data.unep-wcmc.org/datasets/7
Waycott, Michelle, Carlos M. Duarte, Tim J. B. Carruthers, Robert J. Orth, William C. Dennison, Suzanne Olyarnik, Ainsley Calladine, et al. 2009. “Accelerating Loss of Seagrasses across the Globe Threatens Coastal Ecosystems.” Proceedings of the National Academy of Sciences 106 (30): 12377–12381. doi:10.1073/pnas.0905620106.
Short, Frederick, Beth Polidoro, Suzanne Livingstone, Kent E. Carpenter, Bandeira Salomao, Japar Sidik Bujang, Hilconida P. Calumpong, et al. 2011. “Extinction Risk Assessment of the World’s Seagrass Species.” Biological Conservation 144: 1961–1971. doi:10.1016/j.biocon.2011.04.010.
Barbier Edward B., Hacker Sally D., Kennedy Chris, Koch Evamaria W., Stier Adrian C., and Silliman Brian R. 2011. “The Value of Estuarine and Coastal Ecosystem Services.” Ecological Monographs 81 (2): 169–193. doi:10.1890/10-1510.1.
Fourqurean, James W., Carlos M. Duarte, Hilary Kennedy, Núria Marbà, Marianne Holmer, Miguel Angel Mateo, Eugenia T. Apostolaki, et al. 2012. “Seagrass Ecosystems as a Globally Significant Carbon Stock.” Nature Geoscience 5 (7): 505–509. doi:10.1038/ngeo1477.
Image: https://www.flickr.com/photos/flseagrant/29215096422/in/photolist-LvD1k1-4MLdhh-RU3Cnp-atyXAG-7SXFn9-RU3FSk-W1Csfd-Gez1aR-RU3DZx-J1xbts-QuReTW-UZ9xV3-bWsVxt-TtmNA9-UfcZAu-XakFXp-cMpFEf-62xaTY-WPBd9R-2MHp1w-jf7BGA-qateBD-YMohve-UbAgTF-5MZY3-dUivzH-q32F9D-4YRG5P-9sdefY-a54sui-o4V1p7-pKXSaU-MdzR1P-UKSfSg-Gq2sm-e4mCgQ-VgUEmf-m66wTB-MdzQTp-ftsodq-a57iXm-SWXiCS-MdzQPr-Gswiv-rQShWx-RU3ztP-fkSpaN-n4ThPN-fkCGrr-iGKNTd

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CONSIDERATIONS FOR USING SEAGRASS AS COASTAL DEFENSE

Photo credit: Flickr/Dugong Sea Grass

Susceptibility to sea level rise
Enhanced risk mitigation when combined with other ecosystem strategies
Targeted value for high-frequency, smaller scale events
Incorporate valuation results into coastal planning and management decisions

Considerations for using seagrass as risk mitigation strategy include:

Susceptibility to sea level rise. Areas where land subsidence and sea level rise are rapidly changing are least suitable conditions for this ecosystem as a defense mechanism. Because seagrass canopies are relatively short, along the lines of less than 20 inches or 50 centimeters tall, and flexible grasses, they are most effective in shallow water depths of gently sloping coastlines, areas with low boat traffic, and high-density stands.
Targeted value for high-frequency, smaller scale events. Because seagrasses are subtidal, frictional forces are quickly reduced by higher water levels associated with storm surge and flooding during extreme storm events.
Enhanced risk mitigation when combined with other ecosystem strategies. Seagrasses, together with live corals and mangroves, can supply more protection services than any individual habitat or any combination of the two habitats, according to simulation studies.

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References:

Spalding, M. D., McIvor, A. L., Beck, M. W., Koch, E. W., Möller, I., Reed, D. J., Rubinoff, P., Spencer, T., Tolhurst, T. J., Wamsley, T. V., van Wesenbeeck, B. K., Wolanski, E., and Woodroffe, C. D., 2014, Coastal Ecosystems: A Critical Element of Risk Reduction: Conservation Letters, v. 7, no. 3, p. 293-301.
Guannel, Greg, Katie Arkema, Peter Ruggiero, and Gregory Verutes. 2016. “The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience.” PLOS ONE 11 (7): e0158094. doi:10.1371/journal.pone.0158094.
Cunniff, Shannon, and Aaron Schwartz. 2015. Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features. Environmental Defense Fund. https://www.edf.org/sites/default/files/summary_ni_literature_compilation_0.pdf.
Image: https://www.flickr.com/photos/dugongproject/32750442273/in/photolist-RU3ztP-fkSpaN-n4ThPN-fkCGrr-iGKNTd-snvUFm-8jAiz1-aCQimm-UR2z2K-RRtKos-WubG37-bqmo8M-d6mgeN-iGKPdb-iGFUBz-bqUtsq-24Sf8yx-ajTUkS-fd62z5-fHM77G-558v7G-bNQgt2-RRAzAq-atyXEm-RP8KYt-bzVPTY-Rh8uFW-ar4pTT-fHLjBo-fuY8y1-4upicr-ehutAV-D2v3s-bzVPPY-9MUa8L-dBb8GJ-Xyv71d-m8Yx3S-9a6QrK-fsAYi4-2Pnz63-Sy9YtJ-aaAqd6-iGH4NX-EVo4U4-8vUPSV-foi1ma-7agXuu-fsRihq-8Mba1g

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WHAT DO SEAGRASS BEDS COST?

Photo credit: Elisa Alonso Aller

Source: Bayraktarove et al. 2015

Median seagrass restoration cost estimate value is ~US$106,800/hectare

Median seagrass restoration cost estimate value is US$106,782/hectare, according to Bayraktarove et al. 2015. Restoration cost is represented at US$ 2010/ha.
Compared with other ecosystems, coral reefs and seagrass are among the most expensive ecosystems to restore. For coral reefs, seagrass, saltmarshes, and oyster reefs, only small‐scale restoration efforts of <1 ha have been documented. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, is highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%).

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References:

Bayraktarov Elisa, Saunders Megan I., Abdullah Sabah, Mills Morena, Beher Jutta, Possingham Hugh P., Mumby Peter J., and Lovelock Catherine E. 2015. “The Cost and Feasibility of Marine Coastal Restoration.” Ecological Applications 26 (4): 1055–1074. doi:10.1890/15-1077.
Image source: https://www.flickr.com/photos/elisalonso_aller/15040418458/in/photolist-oV55pC-GazgvV-8U1pA1-79hrN-cAtjPC-p2z21d-6541fF-5JxeMA-98MA8N-p2AXFB-Sy9ZBq-jKbrSz-RU3D4K-oZz2ZU-RRtKos-6PFcnb-9ya7ht-5hWLiL-T5qGuJ-7E2HkX-aN5izM-aNDnSt-gR3yin-7hzu4b-WFywFR-75g7wu-MdzR1P-RU3FjX-2Pnz63-Uiqh2C-at3NLP-RRtMsC-RtqC7E-G8hjaj-oYvgsy-WRKomx-RU3FSk-cXjbJu-VMiQ7Y-MdzQPr-asKG1f-Gswiv-WsXkN9-o4FDtt-6J1PHa-qsC1K-6sNdfJ-UD4TEk-ar74Kj-fQbqk1

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DISASTER RISK MANAGEMENT WITH SEAGRASS RESTORATION IN TAMPA BAY

Images: Smithsonian Ocean Portal, Tampa Bay Estuary Program

Annual Report 2016

40,000 acres were successfully restored
Expected outcome: bring water quality improvements, buffer against erosion waves

Increase in Tampa Bay Seagrass Habitat

In Tampa Bay, Florida, the extent of seagrass declined dramatically due to pollution, algae and dredging until, by the 1980s, coverage was only half of what it was in the 1950s.
In 1991, the Tampa Bay Estuary Program was established with the goal of restoring 38,000 acres of seagrass beds. By 2015, efforts had exceeded this goal and 40,000 acres had been created.
Active planting of seagrasses restored the expanse of 3 species: turtle grass, manatee grass and shoal grass. As depicted on the slide, the progress is clear.
Other efforts in combination with the seagrass restoration include:

Water quality improvements through land-use planning and pollution management, as well as newly created oyster reefs and propagation of other filtering species and salt marshes.
Establishment of the Tampa Bay Nitrogen Management Consortium to tackle land-use and runoff management–a public private cooperation spanning more than 40 cities and counties, as well as key industries.

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References:

TBEP. 2018. “Bay Mini-Grants - Tampa Bay Estuary Program.” http://www.tbep.org/index.html.

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THANK YOU

Photo credit: Flickr/Stuart Hamilton

For more information, contact:

Denis Jordy: djordy@worldbank.org

Brenden Jongman: bjongman@worldbank.org

Brenden Van Zanten: bvanzanten@worldbank.org

This knowledge product was created by Gretchen Ellison (WRI), Stefanie Kaupa (GFDRR/World Bank), Suzanne Ozment (WRI), Leah Schleifer (WRI), Brenden Jongman (GFDRR/World Bank), and Todd Gartner (WRI) in April 2018 on behalf of the Global Facility for Disaster Reduction and Recovery, World Bank, and World Resources Institute.
We thank Lauretta Burke (WRI), Gene Clark (UW Sea Grant Institute), Annie Turek (Illinois Department of Natural Resources), and Rich Waite (WRI) for their review and comments on early drafts of this knowledge product.

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References:

Image source: https://www.flickr.com/photos/stuandgravy/2907172/in/photolist-fUcE-h8zmVC-gbqbrM-h8zsFo-h8Amje-h8zbye-h8HHHm-h8Je58-4rBWEV-h8zpbY-h8ztZ5-4fZ1Qf-4rG2s3-gbryJ3-4rBZwg-9yURw6-4NgACu-h8HFBh-h8JKgZ-h8KoZV-4NgxLC-oPrZ6-aDicVL-4NgBiw-51dkZ7-oPs9A-h8zmMQ-3adHmy-h8AqxA-oEctK-9D7jAp-oPs5f-h8zqmq-h8A8bR-sYZ4x-4ipAz7-h8HDc7-65JL5j-h8zoGm-h8Af2H-h8zFRb-h8z81o-h8KoGF-h8Axhe-ikGrh7-h8zwLh-h8zoEQ-h8zsEd-h8znSs-h8ztjj