Man- Environment Relationship

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 • Deforestation • Small infiltration capacity, more surface runoff, soil erosion in upper courses, increase sedimentation and floods in lower courses

5. Deforestation – runoff and sediments

6. Urbanization

7. Modification of the Atmosphere • Sources: • Industrial Revolution • Mining and quarrying • Urbanization • Farming • Harmful effects: • Health • Pollution and Acid Rain • Climate changes

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 • Urbanization • Alter the surface nature & industrial activities • Heat Island effect (micro-climate)

12. Modification of Ecosystem • Agriculture, Industries activities and Urbanization • Simplified ecosystems • Disrupted nutrient cycling • Introduced alien species • Eliminated original species • pollution

13. 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

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 • Conclusion • Shifting Cultivation is Ecologically Destructive

15. Distribution of Shifting cultivation Congo Basin Amazon Basin South-east Asia

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) • Extensive farming

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 activitieslitter and humus are quickly decomposeinfertile 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 humusincrease evaporation, raindrop effect and decrease field capacitysoil structure change

19. Farm cycle – Response to the Env. • Selecting site • Clearing forest • Burning off the dead materials • Planting crops • 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 • 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. • Insuranceagainst 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 ashesare 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 fallowno 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 • The hydrosphere • Soil • 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 • 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

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 • Laterization • Oxisolexpose 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 andstructure 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 becomesecologically destructive.

47. Desert Landscape • Natural Environment • Nomadic Pastoralism • Problem of Over-grazing • Impacts of Over-grazing • Remedies to Desertification

48. Global distribution of desert

49. Natural Environment • Annual rainfallless than250 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

50. Desert Environment