Transcript desertification

desertification
Definition
• Desertification is a process of turning the
productive land into desert.
• A definition of desertification should recognize
that it is a land degradation process that involves
a continuum of change, from slight to very
severe degradation of the plant and soil
resource, and is due to man's activities.
• Desertification is also a situation on the desert
expansion. That means desert is continuously
expanding to the surrounding area.
Where?
• Sub-Saharan Africa, the Middle East,
western Asia, northern Mexico and southeastern South America, western United
States, prairies of Canada, and eastern
Australia. Scientists estimate that 60,000
square kilometers of new desert are now
annually created worldwide.
Causes on desertification
desertification
Climatic
change
Human factors
High pop.
+
Poor / poverty
Impropriate
irrigation
-salinization
Over
grazing
deforest
ation
Global
warming
Over
cropping
↓ Soil fertility ,↓ soil degradation &↓ Soil aridity
Less R”
Cause
Human factors:
High population
-Deforestation---∵demand
more
land and timber for cropping &
building, cutting down to tree
extensively
-Over cropping—-∵demand
for
food crops↑ & the cash crops demanded
by MCDs ↑, ↑shifting cultivation, ↓soil
fertility, secondary growth
Poverty / poor
-Over grazing---∵LDCs have a large international debts,
the cheap labours & the extensive land in LDCs used by MDCs,
in order to pay the debts, →the extensive is suitable for grazing
(i.e., cattle )
Cause
Impropriate irrigation
∴infiltration >E underground water table rises
salinization (鹽鹼化)
Climatic change
-Global warmingCO2↑, T ↑, ice cap melt, flooding in
coastal area , ↓ rainfall, drought , veg. die
-Less rainfalldrought , veg. die
“If the climatic factors are said to be the
main causes of desertification ,then
human activities are going to intensify it.”
Effects on desertification
desertification
Atmosphere
Hydrosphere
Lithosphere
Biosphere
-local climate
-water cycle
-loss of arable
breaks down
salinization
-extinction of
plants &
animals
↓R”
drought
-macro climate
-land intensify the
soil erosion
global warming
Upset the balance of ecosystem
-↓biodiversity
Effects
Atmosphere
1) Micro
(i)↓R”+↑T° ↑T in day time &↓ T in night
time↑ET/reflection ↑diurnal range of T°
(ii) ↑wind speed  ∵no veg cover / shelter
(iii) ↓relative humidity
2)Macro
(i)Global warming
(ii)Sandstormexpanding of desert
Effects
Lithosphere
1)loss of arable land
soil texture change to sandy  ↓cohesive
power (cannot hold water) not suitable for
veg growth
2)intensify the soil erosion
1.↑ deforestationno root to bind the soil
 ↑ soil erosion↑ silting
Effects
Hydrosphere
1)Water cycle breaks down
∵↓R” & ↑ evaporation(∵ no shelter)
 rivers and wells dried up
Biosphere
1)lower the bio-diversity
∵↓R” & unevenly dis.+deforestation
scattered veg. (veg. Is shorter, few
species, less luxuriant)extinction
Effects
Others
1)lower the income
∵R” ↓ crops productivity ↓,
2)use a large amt of $ for soil protection &
recovery
(i.e. UNCED us$1,060m per yr to recover the
deserted land)
How to solve???
LDCs
1.Control the pop. growth / natural increase
by using family planning, in order to
decrease the land use capacity
2.The number of grazing and the rate of
cultivation should not over the carrying
capacity of land
How to solve???
3. improve i)farming & ii)grazing methods,
in other to reduce soil erosion and
salinization
i) suitable timing and amount to carry out irrigation
plant the halophytes (which can adapt salty &
droughted soil) e.g, Chenopodiaceae
ii)sufficient fallowing period
Animal welfare (e.g, Kenya)
How to solve???
4.Legislation: band the deforestation and over
grazing, etc. , in order to balance the ecosystem
of desert.
5.afforestation i.e. plant the wind break trees &
drought resistant plants
6.stone lines (e.g, in Burkina Faso)
7. Building reservoir and canal , (e.g, The Indira
Gandhi Canal)
How to solve???
MDCs
1) international aid(e.g.,Green Peace)
technology, low interest rate of loan &
education
2) scientific research e.g World Association of Soil
and Water Conservation (WASWC)
How to solve???
Both citizens in MDCs & LDCs have
Responsibility
i) Don’t buy valuable halophytes (e.g,Fat choi)
ii) 5R(reuse, reduce, renew, recycle, rethink)
iii) Fund raising
Effectiveness
LDCs
1)Money? LDCs are so poor
2)International aid? lack of technology,efficient farming skill
& low education
3)Attitude? 
X family planning
MDCs
1)Exploitation? try to get more raw materials & resources
from LDCs
2)Human behaviour?? rapid ↑in living standard
& large amt of wastes are produced
Conclusion
The effectiveness of preventing desertification
is depended on the cooperation of MDCs &
LDCs.