Man- Environment Relationship

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Man- Environment Relationship

• HO Pui-sing

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Contents

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

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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

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Deforestation runoff and sediments
Landuse type Average annual rainfall (cm) Average annual run-off (cm) Average annual sediment yield (ton/hectare)
Open land
Cultivated 132 40 50
Pasture 129 38 36
Forest Land
Abandoned fields 129 18 0.29
Depleted hardwoods 129 13 0.22
Pine Plantations 137 2.5 0.045
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Urbanization
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Modification of the Atmosphere

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

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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
• Increase CO2 Level (290ppm to 340ppm)

Gases
N2 78.084
O2 20.947
Ar 0.934
CO2 0.03
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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)

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Modification of Ecosystem

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

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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
Congo Basin
Amazon Basin
South-east Asia
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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

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Farm cycle Response to the Env.

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

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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)

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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.

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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.

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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

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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.

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Abandon and migration contd

• 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

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Conclusion contd

• 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

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Impacts of Shifting Cultivation

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

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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)

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Atmosphere contd

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

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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

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Soil contd

• 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 contd

• 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

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Primary Forest
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Secondary Forest
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Vegetation and animals contd

• 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

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Vegetation and animals contd

• 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.

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Desert Landscape

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

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Global distribution of desert
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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

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Desert Environment
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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

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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

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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.

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Case study 2 Sahara

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

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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.

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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 19th
  century in South Africa

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Reasons of over-grazing

• Man-herds Ratio
• Cattle (115), Camel (120), Sheep (130)
• Traditional Culture
• Number of herds is a sign of wealth.
• Population increase in six-fold since the
  beginning of 20th 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

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Reasons of over-grazing contd

• 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)

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Reasons of over-grazing contd

• Government Policy
• Many independence countries establish after
  1950s 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.

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Reasons of overgrazing contd

• 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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Australia
Savanna
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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

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Impacts of Over-grazing Desertification (contd)

• 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

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Impacts of Over-grazing Desertification (contd)

• 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.

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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.

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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

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Impacts on desert climate contd

• 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.

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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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