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1. Man- Environment Relationship HO Pui-sing
2. Contents Modification of Landforms
Modification of the Atmosphere
Modification of Ecosystem
Tropical Rain Forest Landscape
Tropical Desert Landscape
3. 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
4. Deforestation Natural vegetation
Regulator of natural erosion
Protecting the ground from raindrop
Absorbing runoff (Large infiltration capacity)
Making the slope more cohesive
Small infiltration capacity, more surface runoff, soil erosion in upper courses, increase sedimentation and floods in lower courses
5. Deforestation ? runoff and sediments
7. Modification of the Atmosphere Sources:
Mining and quarrying
Pollution and Acid Rain
8. Harmful effects - health Many pollutants are irritant to eyes
Eg. Smoke, Ozone, Suspended particles?
Dangerous to the respiratory system
Eg. Lung Cancer
9. 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)?..
10. Harmful effects ? climate changes Change the composition of air
Increase CO2 Level (290ppm to 340ppm)
11. 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
Alter the surface nature & industrial activities
Heat Island effect (micro-climate)
12. Modification of Ecosystem Agriculture, Industries activities and Urbanization
Disrupted nutrient cycling
Introduced alien species
Eliminated original species
13. Simplified ecosystem Monoculture
High energy and materials (fertilizers) input
Destroys major nutrient reservoirs (biomass and soil)
Eutrophication ? excess fertilizers added
Conscious - hunting
Unconscious ? disruption of habitats
Decline efficiency ? ecological imbalance
14. 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
Shifting Cultivation is Ecologically Destructive
15. Distribution of Shifting cultivation
16. 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)
17. 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
18. 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
19. Farm cycle ? Response to the Env. Selecting site
Burning off the dead materials
Weeding and harvesting crops
Abandoning the clearing
20. 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)
21. 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.
24. 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.
25. Planting crops Planting is usually timed to take full advantage of rainy season
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
27. Weeding and Harvesting Minimal weeding
Almost no attention until harvest
Too much cultivation increases soil erosion
28. 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.
30. 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.
32. 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
33. 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.
34. 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
35. Impacts of Shifting Cultivation The atmosphere
Vegetation and animals
36. 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)
37. Atmosphere ? cont?d The micro-climate
Forest floor is moist, shade, temperature is relatively low (32oC), wind cannot penetrate and high humidity.
Sunshine reaches the floor, temperature and soil temp. increase (65oC), increase evaporation, decrease relative humidity and increase wind speed
38. 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)
39. Soil Increase leaching
Desilication and accumulation of sesquioxides
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
40. 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
41. 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.
42. 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
43. Primary Forest
44. Secondary Forest
45. 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
46. 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.
47. Desert Landscape Natural Environment
Problem of Over-grazing
Impacts of Over-grazing
Remedies to Desertification
48. Global distribution of desert
49. Natural Environment Annual rainfall less than 250 mm
Rainfall is insufficient
Vegetation is sparse and very localized
It is a harsh Environment
It is impossible for arable farming and very difficult to support domestic animals
50. Desert Environment
54. Human Activities in Desert Desert-dwellers engage many activities
Hunting and gathering
Others: testing missiles, bombs and explosives
55. 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
60. 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.
62. Case study 2: Sahara Two types of Nomadic Pastoralism
True Nomadic Pastoralism
63. 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.
Within the Sahara (Western Sahara)
Out of the Sahara during the driest season (Northern Sahara): Summer in mountains and back to Sahara in winter
64. 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.
65. 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.
66. 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
67. Reasons of over-grazing Man-herds Ratio:
Cattle (1:15), Camel (1:20), Sheep (1:30)
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
68. 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)
69. 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.
70. 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.
72. 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
73. 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
74. 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.
75. 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.
76. 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
79. 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.
80. 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