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
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
Landuse type
Average
annual rainfall
(cm)
Average annual
run-off (cm)
Average annual
sediment yield
(ton/hectare)
Cultivated
132
40
50
Pasture
129
38
36
Abandoned fields
129
18
0.29
Depleted hardwoods
129
13
0.22
Pine Plantations
137
2.5
0.045
Open land
Forest Land
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
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)…..
Harmful effects – climate changes
Change the composition of air
Gases
N2
O2
Ar
CO2
%
78.084
20.947
0.934
0.03
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
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
Distribution of Shifting cultivation
Congo Basin
Amazon 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
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
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
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.
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.
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 (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
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
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.
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
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.
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
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
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
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 overtrampling 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.
Australia
Savanna
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