Man- Environment Relationship

HO Pui-sing

Contents

• Modification of Landforms
• Modification of the Atmosphere
• Modification of Ecosystem
• Tropical Rain Forest Landscape
• Tropical Desert Landscape

Modification of Landforms

• Mining, Quarrying, Deforestation, introduce new plants and animals
• Direct affect on the shape of landforms: Excavating, reclaiming land…
• Deforestation for agriculture and urbanization

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Deforestation

• Natural vegetation
• Regulator of natural erosion
• Protecting the ground from raindrop
• Absorbing runoff (Large infiltration capacity)
• Making the slope more cohesive
• Deforestation
• Small infiltration capacity, more surface runoff, soil erosion in upper courses, increase sedimentation and floods in lower courses

Deforestation – runoff and sediments

Urbanization

Modification of the Atmosphere

• Sources:
• Industrial Revolution
• Mining and quarrying
• Urbanization
• Farming
• Harmful effects:
• Health
• Pollution and Acid Rain
• Climate changes

Harmful effects - health

• Many pollutants are irritant to eyes
• Eg. Smoke, Ozone, Suspended particles…
• Dangerous to the respiratory system
• Eg. Lung Cancer

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Harmful effects – Pollution

• Pollutants:
• Solid: Smoke, Total suspended particles (TSP)
• Liquid: Acid rain
• Gaseous: sulphur dioxide (SO2), Carbon monoxide (CO), Oxides of nitrogen (NOx – NO, NO2)…..

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Harmful effects – climate changes

• Change the composition of air

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• Increase CO2 Level (290ppm to 340ppm)

Harmful effects – Climate changes

• CO2 from fossil fuels combustion
• CO2 level increase, O2 level decrease
• CO2 is greenhouse gas
• Affect global radiation and heat balances
• Global temperature increase
• Alter the rate of evapo-transpiration
• Urbanization
• Alter the surface nature & industrial activities
• Heat Island effect (micro-climate)

Modification of Ecosystem

• Agriculture, Industries activities and Urbanization
• Simplified ecosystems
• Disrupted nutrient cycling
• Introduced alien species
• Eliminated original species
• pollution

Simplified ecosystem

• Monoculture
• High energy and materials (fertilizers) input
• Destroys major nutrient reservoirs (biomass and soil)
• Eutrophication – excess fertilizers added
• Elimination species
• Conscious - hunting
• Unconscious – disruption of habitats
• Decline efficiency – ecological imbalance

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Tropical Rain Forest Landscape

• Where is Shifting Agriculture Practiced
• Characteristics of Shifting Cultivation
• The Relationship between SC and Env.
• Opportunities and constraints posed by Env.
• Response to the opportunities and constraints - Farm Cycle
• Conclusion
• Shifting Cultivation is Ecologically Destructive

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Distribution of Shifting cultivation

Amazon Basin

Congo Basin

South-east Asia

Characteristics of Shifting Cultivation

• Primitive peoples’ cultivation method
• Subsistence farming with tuberous plants
• “Slash and Burn” for clearing forest
• Low man-land ratio
• Primitive method with simple hand tools
• Relatively low yields from crops supplementary with gathering
• No fertilizers and pesticides added
• Periodic migration leaving the clearing (2-3 years)
• Extensive farming

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Relationship between SC and Env.

• Tropical climate – high temp. and high rainfall
• Rapid and high level nutrition cycle
• Heavy leaching, Rapid chemical processes and bacterial activities litter and humus are quickly decompose infertile soil
• Soil fertility maintain by efficient nutrient cycle and most nutrients are locked in biomass

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Relationship between SC and Env.

• Shifting cultivator disrupts an ecosystem equilibrium
• SC take the advantage of transient availability of nitrogen and carbon (nutrients)
• Destroyed the nutrient cycle by clearing
• Depleting effects are accelerated and soil becomes almost completely inorganic
• Oxides layer of the soil expose to air becomes laterite
• Lateritic crusts are hard, compact and very difficult to cultivate and increase surface runoff and soil erosion
• Exposure to air, loss of humus increase evaporation, raindrop effect and decrease field capacity soil structure change

Farm cycle – Response to the Env.

• Selecting site
• Clearing forest
• Burning off the dead materials
• Planting crops
• Weeding and harvesting crops
• Abandoning the clearing

Selecting site

• Fertile soil and ease of clearing
• Primeval forest fertile soil
• Few undergrowth under the dense canopy ease to clear
• Some tribes prefer secondary forest (former site)

Clearing forest

• Clearing forest for having site for cultivation
• Time: end of rainy season to the beginning of dry season
• Lianas, undergrowth and sapling are hacked down. Trees are cut above buttress roots.
• The largest trees may be spared for against soil erosion and they are hard to cut down
• The dead vegetation is piled into heaps and dry out for one or two months.

Burning off the dead vegetation

• Late dry season will set on a fire to burn them off.
• Fire is the easiest way to clear the site.
• The largest trees left for shading for young plants
• Advantages of burning:
• Ashes are also fertility for soil
• Potash, phosphates and decrease in soil acidity.
• Break up the hard lateritic surface
• Dry out the clay soil and develop large cracks into which the ashes accumulate
• Burning debris helps to reduce runoff and soil erosion.

Planting crops

• Planting is usually timed to take full advantage of rainy season
• Mixed cropping
• Advantage of mixed cropping
• maximum return and minimum effort.
• Mixture of crops prevent weeds growth.
• Different growth habits, root systems, demand on soil nutrient.
• Insurance against the failure of any one crop.
• Practice crop rotation for more than one growing season

Weeding and Harvesting

• Minimal weeding
• Almost no attention until harvest
• Too much cultivation increases soil erosion

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Abandon and migration

• 1 to 3 years, yields begin decline
• Humus and ashes are thoroughly used and leach out without any replenishment
• Weeds and undergrowth encroach seriously
• Abandon the clearing and find another site for clearing and cropping.

Abandon and migration – cont’d

• Some tribes may plant tree crops (bananas and coconuts) before moving
• More primitive peoples build only temporary villages for always moving.
• The land will recover the fertility after a long period of time (about 20 years)
• Clearing and migration are conservational measure to restore fertility to depleted soils.

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Conclusion

• Shitting cultivation is a response to the harsh environment.
• Subsistence farming with growing wide range of crops (tuberous plant)
• It is a miniaturized tropical forest
• ‘Slash and burn’ is a method to transfer the stored nutrients from biomass to soil.
• Short period of cultivation and long period of fallow no permanent damage to the environment

Conclusion – cont’d

• Effective means of using rain forest env. and minimize the problems (soil erosion, soil fertility deterioration and vegetation degradation)
• Pre-requisite: primitive technology, small population and sparse distribution.

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Case study

• Note p.14-16 “Shifting Cultivation is ecologically destructive”
• Main points (destroy old balance between man and nature)
• Population increase demand of food increase
• Introduce commercial concept – growing tree crops (rubber, coffee,….)for sell
• Introduce European agricultural techniques and urban development
• More lands for farming
• Field works are left to women
• Shorten the fallow (abandon) period
• Serious soil depletion and soil erosion

Impacts of Shifting Cultivation

• The atmosphere
• The hydrosphere
• Soil
• Vegetation and animals

The Atmosphere

• The global climate
• TRF is a natural filter
• It absorb CO2 and produce O2 through photosynthesis
• Clearance of TRF, increase CO2 (greenhouse gas) content and lead to temperature increase and
• Affect water budget: rainfall changes (increase or decrease)

Atmosphere – cont’d

• The micro-climate
• Normal
• Forest floor is moist, shade, temperature is relatively low (32^oC), wind cannot penetrate and high humidity.
• Clearance
• Sunshine reaches the floor, temperature and soil temp. increase (65^oC), increase evaporation, decrease relative humidity and increase wind speed

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The hydrosphere

• Reduce interception and organic debris supply
• Decrease infiltration capacity and increase surface runoff
• River flow increase (volume, speed and silt load)
• Water chemistry (increase solution load)
• Shape and size of river channels (flooding and sedimentation)

Soil

• Increase leaching
• Desilication and accumulation of sesquioxides
• Laterization
• Oxisol expose to air and through desiccation to become harden layer – latertie.
• Mechanism to check laterization in TRF
• Trees supply plenty of organic matter
• Slows down evaporation from soil

Soil – cont’d

• Break down the nutrient cycle
• Release large amount of nutrients from biomass to soil by burning
• Large amount of nutrients will be transform to ash which is loss by volatilization, wind deflation and water erosion.
• Increase temperature lead to increase rate of decomposition and no humus can be accumulated
• Runoff washes away the available nutrients
• Soil become exhaustion and lead to soil erosion

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Soil – cont’d

• Soil erosion
• Ground become no protection for deforestation
• No interception and rain drops directly on ground surface (rainsplash) to destroy soil structure
• Decrease infiltration capacity and increase surface runoff
• Rills, gullies to badland
• Increase river loads and lead to sedimentation in lower course and causes reservoir silting, obstruct navigate, poor irrigation and flooding.

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Vegetation and animals

• Rain forest was cleared and abandoned by man, secondary forest occurs.
• The floristic and structure are very different from the virgin forest
• The different depends on
• Availability of seeds of primary forest trees
• Length of cultivation before abandonment

Primary Forest

Secondary Forest

Vegetation and animals – cont’d

• The different between secondary forest and primary forest
• Secondary forest is lower and consists of trees of smaller average dimensions.
• Very young secondary forest is remarkably regular and uniform structure (abundance of small climbers and young saplings)
• Poorer in species (one or a small number)
• Secondary forest vegetation is light demanding and intolerant of shade.
• Growing very fast
• Short-live, mature and reproduce early
• Wood has a soft texture and low density

Vegetation and animals – cont’d

• Disturbing the ecological system
• Rainforest lost: West Africa –72%, South east-Asia: 63.5%
• TRF is the centre of the plant evolution of the world. Deforestation may change the future course of plant evolution.
• Knowledge of plant physiology and ecology has been gained from studies in tropics.
• Forest to agricultural, complex food web to simple food chain, encourage certain animals and insects species to multiply
• Shifting agriculture becomes ecologically destructive.

Desert Landscape

• Natural Environment
• Nomadic Pastoralism
• Problem of Over-grazing
• Impacts of Over-grazing
• Remedies to Desertification

Global distribution of desert

Natural Environment

• Annual rainfall less than 250 mm
• Rainfall is insufficient
• Erratic
• Unpredictable
• Vegetation is sparse and very localized
• It is a harsh Environment
• It is impossible for arable farming and very difficult to support domestic animals

Desert Environment

Human Activities in Desert

• Desert-dwellers engage many activities
• Hunting and gathering
• Nomadic herding
• Oasis cultivation
• Mining
• Oil industry
• Tourism
• Others: testing missiles, bombs and explosives

Pastoralism

• The practice of keeping animals for meat and milk, fibre and hides
• It is a traditional form of subsistence farming
• Tribal people wandering in semi-arid land in search for grazing land
• Activity of nomads shifts from one section of land to another
• Fixed patterns of seasonal (rainfall) movement
• By this grazing cycle, soil structure, soil fertility and carrying capacity of desert environment can be conserved

Case study 1: Xinjiang

• Location: Junggar Pendi
• Rainfall: 150-300 mm
• Herds: sheep, cattle, horse, camels
• Types of nomadic grazing
• Aimless roaming (Kirghiz): ban by government policy
• Transhumance (Tian shan): encampments for summer (mountain) and winter (pediplain) pastures.

Case study 2: Sahara

• Two types of Nomadic Pastoralism
• True Nomadic Pastoralism
• Semi-nomads

True Nomadic Pastoralism

• Tribes have to continuous on the move
• Scouts look for fresh pasture and animals are driven there immediately.
• They move once a month usually in constant routes
• They are in small family groups with minimum baggage for easy to move.
• Movements
• Within the Sahara (Western Sahara)
• Out of the Sahara during the driest season (Northern Sahara): Summer in mountains and back to Sahara in winter

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Semi-nomads

• Southern hills of the Mountain Atlas
• North and the coastal fringe of Libya
• Southern perimeter of the desert
• They drive their flocks according to seasons and rain.
• They also carry out subsistence farming and grow barley, wheat and fruits.
• Ban for government policy.

Conclusion

• For thousand of years, nomadic Pastoralism is a flexible and efficient form of livelihood in deserts.
• It is well adapted to the harsh environment with low carrying capacity.
• Equilibrium can be maintained by this rotating cycle.
• Soil and vegetation can be regenerated and recovered.
• It is one of the best adaptation to harsh conditions.
• Pre-requisite: limited human and animal population which are not excess the carrying capacity.

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The problem of Over-grazing

• Mobility, shorter life expectancies, low human and animal populations that make ecological equilibrium possible.
• Grazing system could only support a small population.
• This equilibrium maintain thousands of year until last century.
• Eg. Semi-arid area increase 50% during 19^th century in South Africa

Reasons of over-grazing

• Man-herds Ratio:
• Cattle (1:15), Camel (1:20), Sheep (1:30)
• Traditional Culture:
• Number of herds is a sign of wealth.
• Population increase in six-fold since the beginning of 20^th century in north Africa
• Population explosion for following reasons:
• Improving medical services
• decrease death rate
• International aid programmes
• reduce level of starvation by supplying food from outside
• Improving law enforcement and tribal settling programmes
• reduce number of deaths caused by warfare

Reasons of over-grazing – cont’d

• Problems from population increase:
• Expand their herd size for living
• Good climate - increase herd size
• Dryness climate – unwilling to reduce the herd size
• Good climate return – restock herd size more quickly.
• Nomads are forced to go back to the fallow graze land more frequently, shorter fallow period, shorter recover period (both soil and vegetation).
• Nomads are forced to expand into the marginal semi-arid area (desertification)

Reasons of over-grazing – cont’d

• Government Policy
• Many independence countries establish after 1950’s in the world and political boundaries form
• Restricted movement of people and animals for population control, revenue collection and resources exploitation.
• Nomads cannot follow the rain pattern to move freely
• Tribesmen are encouraged to settle and cultivate
• More herds are concentrated on a smaller area, that means greater concentration of grazing pressure on poor vegetation and greater danger of over-trampling of soil by animals.

Reasons of overgrazing – cont’d

• Economic – Commercial grazing
• The success of commercial grazing in North America and Australia
• Many African countries develop commercial grazing.
• Increase herds size for sale.
• Pre-requisite: Water supply is the main point to the success of this industry.

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Savanna

Australia

Impacts of Over-grazing - Desertification

• Destruction of vegetation
• Over-grazing excess the carrying capacity of pasture.
• Sheep – grazing down to root level
• Goat – destruction of trees and seedlings
• Large herds size – serve to destroy the plant cover
• Palatable species were replaced by non-palatable grasses or a loss of regeneration capacity, desiccation of land, destruction of soil structure and soil erosion

Impacts of Over-grazing – Desertification (cont’d)

• Destruction of soil
• Drill new wells to provide water for herds.
• Concentration of the livestock around fixed points.
• Vegetation in the surrounding areas was totally denuded.
• Severe trampling results in destruction of soil structure

Impacts of Over-grazing – Desertification (cont’d)

• Removal of vegetation cover
• Soil directly exposed to the desiccation effect of the sun and wind erosion.
• Soil erosion is irreversible and vegetation may be eliminated forever.
• Nomads are forced to migrate into less arid areas, and so the cycle of environmental degradation is repeated continuously and in a self-accelerating process - Desertification.

Desertification

• Desertification is the diminution or destruction of the biological potential of the land, and can lead ultimately to desert-like conditions.
• It is an aspect of the widespread deterioration of ecosystems, and has diminished or destroyed the biological potential,
• i.e. plant and animal production, for multiple use purposes at a time when increased productivity is needed to support growing populations in quest of development.

Impacts on desert climate

• Removal of vegetation
• Increase surface albedo leads to a decrease of absorbing in incoming radiation of the land surface.
• Increase in the radioactive cooling of the air.
• Air would sink to land surface to maintain thermal equilibrium by adiabatic compression; convection and rainfall would be suppressed.
• Lower rainfall lead to further decrease in plant cover

Impacts on desert climate – cont’d

• Removal of vegetation
• Decrease of a kind of bacteria which is a very efficient freezing / condensation nuclei.
• Reduce the probability of convective rainfall
• Increasing surface albedo and reducing freezing nuclei, all which intensifies desertification.

Remedies to Desertification

• Increase the production of meat by keeping camels instead of sheep, goats and cattle.
• Plant prickly pear as a source of animal fed.
• Transfer people to other areas or activities, forcing migration, providing education and control over the use of land and water.
• Afforestation. Provide a green belt to stop the expansion of desert. Eg. Calophyllum inophyllum
• Use drip irrigation

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