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Chapter 55

Conservation Biology and Restoration Ecology

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Overview: The Biodiversity Crisis

Conservation biology integrates the following fields to conserve biological diversity at all levels
Ecology
Evolutionary biology
Physiology
Molecular biology
Genetics
Behavioral ecology

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Restoration ecology applies ecological principles

In an effort to return degraded ecosystems to conditions as similar as possible to their natural state

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Figure 55.1

Tropical forests

Contain some of the greatest concentrations of species
Are being destroyed at an alarming rate

Figure 55.1

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Throughout the biosphere, human activities

Are altering ecosystem processes on which we and other species depend

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Concept 55.1: Human activities threaten Earth’s biodiversity
Rates of species extinction

Are difficult to determine under natural conditions

The current rate of species extinction is high

And is largely a result of ecosystem degradation by humans

Humans are threatening Earth’s biodiversity

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The Three Levels of Biodiversity

Biodiversity has three main components

Genetic diversity
Species diversity
Ecosystem diversity

Genetic diversity in a vole population

Species diversity in a coastal redwood ecosystem

Community and ecosystem diversity

across the landscape of an entire region

Figure 55.2

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Genetic Diversity

Genetic diversity comprises

The genetic variation within a population
The genetic variation between populations

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Species Diversity

Species diversity

Is the variety of species in an ecosystem or throughout the biosphere

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An endangered species

Is one that is in danger of becoming extinct throughout its range

Threatened species

Are those that are considered likely to become endangered in the foreseeable future

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Conservation biologists are concerned about species loss

Because of a number of alarming statistics regarding extinction and biodiversity

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(a) Philippine eagle

Harvard biologist E. O. Wilson has identified the Hundred Heartbeat Club

Species that number fewer than 100 individuals and are only that many heartbeats from extinction

(a) Philippine eagle

(b) Chinese river � dolphin

(c) Javan � rhinoceros

Figure 55.3a–c

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Ecosystem Diversity

Ecosystem diversity

Identifies the variety of ecosystems in the biosphere
Is being affected by human activity

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Biodiversity and Human Welfare

Human biophilia

Allows us to recognize the value of biodiversity for its own sake

Species diversity

Brings humans many practical benefits

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Benefits of Species and Genetic Diversity

Many pharmaceuticals

Contain substances originally derived from plants

Figure 55.4

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The loss of species

Also means the loss of genes and genetic diversity

The enormous genetic diversity of organisms on Earth

Has the potential for great human benefit

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Ecosystem Services

Ecosystem services encompass all the processes

Through which natural ecosystems and the species they contain help sustain human life on Earth

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Ecosystem services include

Purification of air and water
Detoxification and decomposition of wastes
Cycling of nutrients
Moderation of weather extremes
And many others

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Four Major Threats to Biodiversity

Most species loss can be traced to four major threats

Habitat destruction
Introduced species
Overexploitation
Disruption of “interaction networks”

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Habitat Destruction

Human alteration of habitat

Is the single greatest threat to biodiversity throughout the biosphere

Massive destruction of habitat

Has been brought about by many types of human activity

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Figure 55.5

Many natural landscapes have been broken up

Fragmenting habitat into small patches

Figure 55.5

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In almost all cases

Habitat fragmentation and destruction leads to loss of biodiversity

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Introduced Species

Introduced species

Are those that humans move from the species’ native locations to new geographic regions

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(a) Brown tree � snake, intro-� duced to Guam � in cargo

Introduced species that gain a foothold in a new habitat

Usually disrupt their adopted community

(a) Brown tree � snake, intro-� duced to Guam � in cargo

(b) Introduced kudzu thriving in South Carolina

Figure 55.6a, b

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Overexploitation

Overexploitation refers generally to the human harvesting of wild plants or animals

At rates exceeding the ability of populations of those species to rebound

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Figure 55.7

The fishing industry

Has caused significant reduction in populations of certain game fish

Figure 55.7

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Disruption of Interaction Networks

The extermination of keystone species by humans

Can lead to major changes in the structure of communities

Figure 55.8

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Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitat
Biologists focusing on conservation at the population and species levels

Follow two main approaches

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Small-Population Approach

Conservation biologists who adopt the small-population approach

Study the processes that can cause very small populations finally to become extinct

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The Extinction Vortex

A small population is prone to positive-feedback loops

That draw the population down an extinction vortex

Small

population

Inbreeding

Genetic

drift

Lower �reproduction

Higher �mortality

Loss of

genetic

variability

Reduction in

individual

fitness and

population

adaptability

Smaller

population

Figure 55.9

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The key factor driving the extinction vortex

Is the loss of the genetic variation necessary to enable evolutionary responses to environmental change

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Case Study: The Greater Prairie Chicken and the Extinction Vortex

Populations of the greater prairie chicken

Were fragmented by agriculture and later found to exhibit decreased fertility

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As a test of the extinction vortex hypothesis

Scientists imported genetic variation by transplanting birds from larger populations

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EXPRIMENT

The declining population rebounded

Confirming that it had been on its way down an extinction vortex

EXPRIMENT

Researchers observed that the population �collapse of the greater prairie chicken was mirrored in a reduction in �fertility, as measured by the hatching rate of eggs. Comparison of �DNA samples from the Jasper County, Illinois, population with DNA� from feathers in museum specimens showed that genetic variation �had declined in the study population. In 1992, researchers began �experimental translocations of prairie chickens from Minnesota, �Kansas, and Nebraska in an attempt to increase genetic variation.

RESULTS

After translocation (blue arrow), the viability of eggs rapidly improved, and the population rebounded.

CONCLUSION

The researchers concluded that lack of genetic � variation had started the Jasper County population of prairie� chickens down the extinction vortex.

Number of male birds

(a) Population dynamics

(b) Hatching rate

200

150

100

50

0

1970

1975

1980

1985

1990

1995

2000

Year

Eggs hatched (%)

100

90

80

70

60

50

40

30

1970-74

1975-79

1980-84

1985-89

1990

1993-97

Years

Figure 55.10

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Minimum Viable Population Size

The minimum viable population (MVP)

Is the minimum population size at which a species is able to sustain its numbers and survive

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A population viability analysis (PVA)

Predicts a population’s chances for survival over a particular time
Factors in the MVP of a population

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Effective Population Size

A meaningful estimate of MVP

Requires a researcher to determine the effective population size, which is based on the breeding size of a population

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Case Study: Analysis of Grizzly Bear Populations

One of the first population viability analyses

Was conducted as part of a long-term study of grizzly bears in Yellowstone National Park

Figure 55.11

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Number of individuals

This study has shown that the grizzly bear population

Has grown substantially in the past 20 years

Number of individuals

150

100

50

0

1973

1982

1991

2000

Females with cubs

Cubs

Year

Figure 55.12

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Declining-Population Approach

The declining-population approach

Focuses on threatened and endangered populations that show a downward trend, regardless of population size
Emphasizes the environmental factors that caused a population to decline in the first place

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Steps for Analysis and Intervention

The declining-population approach

Requires that population declines be evaluated on a case-by-case basis
Involves a step-by-step proactive conservation strategy

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Case Study: Decline of the Red-Cockaded Woodpecker

Red-cockaded woodpeckers

Require specific habitat factors for survival
Had been forced into decline by habitat destruction

(a) A red-cockaded woodpecker perches at the � entrance to its nest site in a longleaf pine.

(b) Forest that can � sustain red-cockaded � woodpeckers has � low undergrowth.

(c) Forest that cannot sustain red-cockaded � woodpeckers has high, dense undergrowth that � impacts the woodpeckers’ access to feeding grounds.

Figure 55.13a–c

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In a study where breeding cavities were constructed

New breeding groups formed only in these sites

On the basis of this experiment

A combination of habitat maintenance and excavation of new breeding cavities has enabled a once-endangered species to rebound

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Weighing Conflicting Demands

Conserving species often requires resolving conflicts

Between the habitat needs of endangered species and human demands

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Concept 55.3: Landscape and regional conservation aim to sustain entire biotas
In recent years, conservation biology

Has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes

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One goal of landscape ecology, of which ecosystem management is part

Is to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planning

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Landscape Structure and Biodiversity

The structure of a landscape

Can strongly influence biodiversity

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Fragmentation and Edges

The boundaries, or edges, between ecosystems

Are defining features of landscapes

(a) Natural edges. Grasslands give way to forest ecosystems in � Yellowstone National Park.

(b) Edges created by human activity. Pronounced edges (roads) � surround clear-cuts in this photograph of a heavily logged rain � forest in Malaysia.

Figure 55.14a, b

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As habitat fragmentation increases

And edges become more extensive, biodiversity tends to decrease

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Figure 55.15

Research on fragmented forests has led to the discovery of two groups of species

Those that live in forest edge habitats and those that live in the forest interior

Figure 55.15

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Corridors That Connect Habitat Fragments

A movement corridor

Is a narrow strip of quality habitat connecting otherwise isolated patches

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Figure 55.16

In areas of heavy human use

Artificial corridors are sometimes constructed

Figure 55.16

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Movement corridors

Promote dispersal and help sustain populations

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Establishing Protected Areas

Conservation biologists are applying their understanding of ecological dynamics

In establishing protected areas to slow the loss of biodiversity

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Much of the focus on establishing protected areas

Has been on hot spots of biological diversity

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Finding Biodiversity Hot Spots

A biodiversity hot spot is a relatively small area

With an exceptional concentration of endemic species and a large number of endangered and threatened species

Terrestrial �biodiversity �hot spots

Equator

Figure 55.17

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Biodiversity hot spots are obviously good choices for nature reserves

But identifying them is not always easy

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Philosophy of Nature Reserves

Nature reserves are biodiversity islands

In a sea of habitat degraded to varying degrees by human activity

One argument for extensive reserves

Is that large, far-ranging animals with low-density populations require extensive habitats

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Biotic boundary for

short-term survival;

MVP is 50 individuals.

In some cases

The size of reserves is smaller than the actual area needed to sustain a population

Biotic boundary for

short-term survival;

MVP is 50 individuals.

Biotic boundary for

long-term survival;

MVP is 500 individuals.

Grand Teton

National Park

Wyoming

Idaho

43

42

41

40

0

50

100

Kilometers

Snake R.

Yellowstone

National

Park

Shoshone R.

Montana

Wyoming

Montana

Idaho

Madison R.

Gallatin R.

Yellowstone R.

Figure 55.18

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Zoned Reserves

The zoned reserve model recognizes that conservation efforts

Often involve working in landscapes that are largely human dominated

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(a) Boundaries of the zoned reserves are indicated by black outlines.

Zoned reserves

Are often established as “conservation areas”

(a) Boundaries of the zoned reserves are indicated by black outlines.

(b) Local schoolchildren marvel at the diversity of life in one of � Costa Rica’s reserves.

Nicaragua

Costa

Rica

Panama

National park land

Buffer zone

PACIFIC OCEAN

CARIBBEAN SEA

Figure 55.19a, b

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Figure 55.20

Some zoned reserves in the Fiji islands are closed to fishing

Which actually helps to improve fishing success in nearby areas

Figure 55.20

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Concept 55.4: Restoration ecology attempts to restore degraded ecosystems to a more natural state
The larger the area disturbed

The longer the time that is required for recovery

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Recovery time (years)

(log scale)

Whether a disturbance is natural or caused by humans

Seems to make little difference in this size-time relationship

Recovery time (years)

(log scale)

10⁴

1,000

100

10

1

10^3

10^2

10^1

1

10

100

1,000

10⁴

Natural disasters

Human-caused disasters

Natural OR human-

caused disasters

Meteor

strike

Groundwater

exploitation

Industrial

pollution

Urbanization

Salination

Modern

agriculture

Flood

Volcanic

eruption

Acid

rain

Forest

fire

Nuclear

bomb

Tsunami

Oil

spill

Slash

& burn

Land-

slide

Tree

fall

Lightning

strike

Spatial scale (km²)

(log scale)

Figure 55.21

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One of the basic assumptions of restoration ecology

Is that most environmental damage is reversible

Two key strategies in restoration ecology

Are bioremediation and augmentation of ecosystem processes

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Bioremediation

Bioremediation

Is the use of living organisms to detoxify ecosystems

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Biological Augmentation

Biological augmentation

Uses organisms to add essential materials to a degraded ecosystem

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Exploring Restoration

The newness and complexity of restoration ecology

Require scientists to consider alternative solutions and adjust approaches based on experience

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Truckee River, Nevada.

Exploring restoration worldwide

Truckee River, Nevada.

Kissimmee River, Florida.

Equator

Figure 55.22

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Tropical dry forest, Costa Rica.

Succulent Karoo, South Africa.

Rhine River, Europe.

Coastal Japan.

Figure 55.22

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Concept 55.5: Sustainable development seeks to improve the human condition while conserving biodiversity
Facing increasing loss and fragmentation of habitats

How can we best manage Earth’s resources?

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Sustainable Biosphere Initiative

The goal of this initiative is to define and acquire the basic ecological information necessary

For the intelligent and responsible development, management, and conservation of Earth’s resources

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Case Study: Sustainable Development in Costa Rica

Costa Rica’s success in conserving tropical biodiversity

Has involved partnerships between the government, other organizations, and private citizens

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Infant mortality (per 1,000 live births)

Human living conditions in Costa Rica

Have improved along with ecological conservation

Infant mortality (per 1,000 live births)

200

150

100

50

0

1900

1950

2000

80

70

60

50

40

30

Year

Life expectancy

Infant mortality

Life expectancy (years)

Figure 55.23

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Biophilia and the Future of the Biosphere

Our modern lives

Are very different from those of early humans who hunted and gathered and painted on cave walls

(a) Detail of animals in a Paleolithic mural, Lascaux, France

Figure 55.24a

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(b) Biologist Carlos Rivera Gonzales examining a tiny tree frog in � Peru

But our behavior

Reflects remnants of our ancestral attachment to nature and the diversity of life, the concept of biophilia

(b) Biologist Carlos Rivera Gonzales examining a tiny tree frog in � Peru

Figure 55.24b

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Our innate sense of connection to nature

May eventually motivate a realignment of our environmental priorities