Man- Environment Relationship

HO Pui-sing

Contents

Modification of LandformsModification of the AtmosphereModification of EcosystemTropical Rain Forest LandscapeTropical Desert Landscape

Modification of Landforms

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

DeforestationNatural vegetation

Regulator of natural erosionProtecting the ground from raindropAbsorbing runoff (Large infiltration capacity)Making the slope more cohesive

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

Deforestation – runoff and sedimentsLanduse 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

Urbanization

Modification of the AtmosphereSources:

Industrial RevolutionMining and quarryingUrbanizationFarming

Harmful effects:HealthPollution and Acid RainClimate changes

Harmful effects - health

Many pollutants are irritant to eyesEg. Smoke, Ozone, Suspended particles…

Dangerous to the respiratory systemEg. Lung Cancer

Harmful effects – Pollution

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

Harmful effects – climate changes

Change the composition of air

Increase CO2 Level (290ppm to 340ppm)

Gases %

N2 78.084O2 20.947Ar 0.934

CO2 0.03

Harmful effects – Climate changesCO2 from fossil fuels combustion

CO2 level increase, O2 level decreaseCO2 is greenhouse gasAffect global radiation and heat balancesGlobal temperature increaseAlter the rate of evapo-transpiration

UrbanizationAlter the surface nature & industrial activitiesHeat Island effect (micro-climate)

Modification of EcosystemAgriculture, Industries activities and Urbanization

Simplified ecosystemsDisrupted nutrient cyclingIntroduced alien speciesEliminated original speciespollution

Simplified ecosystemMonoculture

High energy and materials (fertilizers) inputDestroys major nutrient reservoirs (biomass and soil)

Eutrophication – excess fertilizers addedElimination species

Conscious - huntingUnconscious – disruption of habitats

Decline efficiency – ecological imbalance

Tropical Rain Forest Landscape

Where is Shifting Agriculture PracticedCharacteristics of Shifting CultivationThe Relationship between SC and Env.

Opportunities and constraints posed by Env.Response to the opportunities and constraints - Farm CycleConclusion

Shifting Cultivation is Ecologically Destructive

Distribution of Shifting cultivation

Amazon Basin

Congo Basin

South-east Asia

Characteristics of Shifting CultivationPrimitive peoples’ cultivation methodSubsistence farming with tuberous plants“Slash and Burn” for clearing forestLow man-land ratioPrimitive method with simple hand toolsRelatively low yields from crops supplementary with gatheringNo fertilizers and pesticides addedPeriodic migration leaving the clearing (2-3 years)Extensive farming

Relationship between SC and Env.Tropical climate – high temp. and high rainfallRapid and high level nutrition cycleHeavy leaching, Rapid chemical processes and bacterial activities litter and humus are quickly decompose infertile soilSoil fertility maintain by efficient nutrient cycle and most nutrients are locked in biomass

Relationship between SC and Env.Shifting cultivator disrupts an ecosystem equilibriumSC take the advantage of transient availability of nitrogen and carbon (nutrients)Destroyed the nutrient cycle by clearingDepleting effects are accelerated and soil becomes almost completely inorganicOxides layer of the soil expose to air becomes lateriteLateritic crusts are hard, compact and very difficult to cultivate and increase surface runoff and soil erosionExposure to air, loss of humus increase evaporation, raindrop effect and decrease field capacity soil structure change

Farm cycle – Response to the Env.Selecting siteClearing forestBurning off the dead materialsPlanting cropsWeeding and harvesting cropsAbandoning the clearing

Selecting site

Fertile soil and ease of clearingPrimeval forest fertile soilFew undergrowth under the dense canopy ease to clearSome tribes prefer secondary forest (former site)

Clearing forestClearing forest for having site for cultivationTime: end of rainy season to the beginning of dry seasonLianas, 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 downThe dead vegetation is piled into heaps and dry out for one or two months.

Burning off the dead vegetationLate 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 plantsAdvantages of burning:

Ashes are also fertility for soilPotash, phosphates and decrease in soil acidity.Break up the hard lateritic surfaceDry out the clay soil and develop large cracks into which the ashes accumulateBurning debris helps to reduce runoff and soil erosion.

Planting cropsPlanting is usually timed to take full advantage of rainy seasonMixed croppingAdvantage 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 HarvestingMinimal weedingAlmost no attention until harvestToo much cultivation increases soil erosion

Abandon and migration1 to 3 years, yields begin declineHumus and ashes are thoroughly used and leach out without any replenishmentWeeds and undergrowth encroach seriouslyAbandon the clearing and find another site for clearing and cropping.

Abandon and migration – cont’dSome tribes may plant tree crops (bananas and coconuts) before movingMore 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.

ConclusionShitting 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.

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 increaseIntroduce commercial concept – growing tree crops (rubber, coffee,….)for sellIntroduce European agricultural techniques and urban developmentMore lands for farmingField works are left to womenShorten the fallow (abandon) periodSerious soil depletion and soil erosion

Impacts of Shifting Cultivation

The atmosphereThe hydrosphereSoilVegetation and animals

The AtmosphereThe global climate

TRF is a natural filterIt absorb CO2 and produce O2 through photosynthesisClearance of TRF, increase CO2 (greenhouse gas) content and lead to temperature increase andAffect water budget: rainfall changes (increase or decrease)

Atmosphere – cont’dThe micro-climateNormal

Forest floor is moist, shade, temperature is relatively low (32oC), wind cannot penetrate and high humidity.

ClearanceSunshine reaches the floor, temperature and soil temp. increase (65oC), increase evaporation, decrease relative humidity and increase wind speed

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

SoilIncrease leaching

Desilication and accumulation of sesquioxides

LaterizationOxisol 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’dBreak down the nutrient cycle

Release large amount of nutrients from biomass to soil by burningLarge 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 accumulatedRunoff washes away the available nutrientsSoil become exhaustion and lead to soil erosion

Soil – cont’dSoil erosion

Ground become no protection for deforestationNo interception and rain drops directly on ground surface (rainsplash) to destroy soil structureDecrease infiltration capacity and increase surface runoff Rills, gullies to badlandIncrease river loads and lead to sedimentation in lower course and causes reservoir silting, obstruct navigate, poor irrigation and flooding.

Vegetation and animalsRain forest was cleared and abandoned by man, secondary forest occurs.The floristic and structure are very different from the virgin forestThe different depends on

Availability of seeds of primary forest treesLength of cultivation before abandonment

Primary Forest

Secondary Forest

Vegetation and animals – cont’dThe 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’dDisturbing the ecological systemRainforest 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 multiplyShifting agriculture becomes ecologically destructive.

Desert Landscape

Natural EnvironmentNomadic PastoralismProblem of Over-grazingImpacts of Over-grazingRemedies to Desertification

Global distribution of desert

Natural EnvironmentAnnual rainfall less than 250 mmRainfall is insufficientErraticUnpredictableVegetation is sparse and very localizedIt is a harsh EnvironmentIt is impossible for arable farming and very difficult to support domestic animals

Desert Environment

Human Activities in DesertDesert-dwellers engage many activitiesHunting and gatheringNomadic herdingOasis cultivationMiningOil industryTourismOthers: testing missiles, bombs and explosives

PastoralismThe practice of keeping animals for meat and milk, fibre and hidesIt is a traditional form of subsistence farmingTribal people wandering in semi-arid land in search for grazing landActivity of nomads shifts from one section of land to anotherFixed patterns of seasonal (rainfall) movementBy this grazing cycle, soil structure, soil fertility and carrying capacity of desert environment can be conserved

Case study 1: XinjiangLocation: Junggar PendiRainfall: 150-300 mmHerds: sheep, cattle, horse, camelsTypes of nomadic grazing

Aimless roaming (Kirghiz): ban by government policyTranshumance (Tian shan): encampments for summer (mountain) and winter (pediplain) pastures.

Case study 2: Sahara

Two types of Nomadic PastoralismTrue Nomadic PastoralismSemi-nomads

True Nomadic PastoralismTribes have to continuous on the moveScouts look for fresh pasture and animals are driven there immediately.They move once a month usually in constant routesThey 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

Semi-nomadsSouthern hills of the Mountain AtlasNorth and the coastal fringe of LibyaSouthern perimeter of the desertThey drive their flocks according to seasons and rain.They also carry out subsistence farming and grow barley, wheat and fruits.Ban for government policy.

ConclusionFor 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.

The problem of Over-grazingMobility, 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

Reasons of over-grazingMan-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 20th century in north AfricaPopulation 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’dProblems from population increase:Expand their herd size for living

Good climate - increase herd sizeDryness climate – unwilling to reduce the herd sizeGood 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’dGovernment PolicyMany 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 cultivateMore 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’dEconomic – Commercial grazingThe success of commercial grazing in North America and AustraliaMany African countries develop commercial grazing.Increase herds size for sale.Pre-requisite: Water supply is the main point to the success of this industry.

Savanna

Australia

Impacts of Over-grazing - Desertification

Destruction of vegetationOver-grazing excess the carrying capacity of pasture.

Sheep – grazing down to root levelGoat – destruction of trees and seedlingsLarge 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 soilDrill 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 coverSoil 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.

DesertificationDesertification 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 climateRemoval of vegetationIncrease 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’dRemoval of vegetationDecrease of a kind of bacteria which is a very efficient freezing / condensation nuclei.Reduce the probability of convective rainfallIncreasing surface albedo and reducing freezing nuclei, all which intensifies desertification.

Remedies to DesertificationIncrease 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