Transcript Advance desertification_Lecture 3x

Desertification phenomenon
“Desertification is one of the world’s most alarming
processes of environmental degradation”
“For most drylands dwellers, life is hard and the future
often precarious. They live on the ecological, economic
and social margins. It is essential that we do not
neglect them or the fragile habitats on which they
depend,”
Kofi Annan _Former UN secretary general
International Year of Desert and Desertification, 2006
 Drylands cover more than 40 per cent of the earth's
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surface.
There are nearly 2 billion drylands dwellers.
It affects one third of the earth’s surface and over a billion
people.
More than 110 countries, particularly in Africa, Asia and
Latin America, have drylands that are potentially
threatened by desertification.
24 billion tons of fertile soil disappear annually.
Each year, desertification and drought cause an estimated
$42 billion in lost agricultural production.
The middle east hold up to 93% of drylands, while two
thirds of the African continent is desert or drylands.
Desert name
location
Area (km2)
Antarctic desert
Antarctica
13,829,430
Arctic
Alaska, Canada, Finland,
Greenland(Denmark), Iceland,
Norway, Russia and Sweden
13,726,937
Sahara
Algeria, Chad, Egypt, Eritrea, Libya, M
ali, Mauritania, Morocco, Niger, Sudan
, Tunisia and Western Sahara
900,000
Arabian Desert
Iraq, Jordan, Kuwait, Oman, Qatar, Sa
udi Arabia, United Arab Emirates
and Yemen
2,330,000
Gobi Desert
China and Mongolia
1,300,000
Kalahari Desert
Angola, Botswana, Namibia and South
Africa
900,000
Patagonian Desert
Argentina and Chile
670,000
Great Victoria Desert
Australia
647,000
Syrian Desert
Iraq, Jordan and Syria
520,000
 Deserts of Saudi Arabia are originated from the vast
northern desert (border of Syria, Iraq and Jordon)
 Desert are formed as a result of sand dune movement
from the northern and north western side of the
peninsula especially in summer.
 Major deserts are Alnofod, Aldahna, Alsaman and The
empty quarter.
 Desertification is simply the processes that results in
the degradation of the environment and ecosystems
(i.e. low ground water levels, Stalinization of top soil
and water, low vegetation cover, soil erosion)
 All these process would increase the total area of the
desert replacing vegetation.
 The Desertification term was first used by the French
botanist Aubreville in 1949, to refer to the
transformation of productive agricultural land into a
desert-like condition.
 Desertification term has since been widely used as
human been started to sense the scope of the problem,
desert lands were increasing as human population
along with food demands increase.
 This of course was much more noticed and significant
in arid and semi arid lands where food and water
resources scarce. (thus any minimal changes in the
fragile ecosystem can result in a disaster).
 For example, in 1963, the eastern coast of Africa (the
southern border of the Sahara desert) containing Lake
Chand has suffered continuous drought for almost 4
decades.
 This prolong drought has decreased the size of the
lake to 1/3 its original size and resulted in the drying of
the whole land extending to the borders of the Sahara
desert in the north.
1963
1987
1973
1997
Lake Chad is located on the border of 4 African countries : Chad, Nigeria, Niger, Cameroon
was one day the sixth largest lake in the world and as a result of successive droughts since
 Desertification definition: “a process by which natural
or artificial degradation of land resources occur under
the effect of extreme drought in climate and soil”.
UNCED, 1992
 Kassas (1995):
Desertification: degradation and corrosion of land
resources due to natural and human factors.
Drought: the retention of rain resulting in land
aridity.
1.
Human causes: overgrazing, Farming of Average
Land, Destruction of Plants in Dry Regions,
Incorrect Irrigation, increased population, poverty,
policy and instrumental shortcomings.
2.
Natural causes: Climate change (drought/rain
retention, increased wind/ high evapotranspiration)
1.
Overgrazing: was not as large of a problem long ago
because animals would move in response to rainfall,
people would move with the animals so it prevented
overgrazing in such areas. Now, humans have a steady
food supply so they do not have to move about.
Therefore, people use fences to keep their animals in
one place which causes overgrazing.
•Around the 1950’s, people
settled into the Sahel region, in
areas where there was water.
•Overgrazing rate increased
overtime resulting in the
destruction of perennial shrubs
and replaced with annuals.
•Annual shrubs were also
overgrazed leaving bare soil
vulnerable to degradation.
• top soil was washed away exposing the bed rocks
and thus plants were not able to grow because their
roots could not penetrate hard clay layers.
2.
Farming of Average Land: is causing desertification
worldwide. Farmers are clearing average land, and
using it reducing the fertility and richness of the soil.
People should let the average land replenish itself
before farming.
3.
Destruction of Plants in Dry Regions: is causing
desertification via cutting down tress to use as a
source of fuel. Trees has a major role in soil protection
and cutting them down would dry the bare soil and
get blown away by wind.
4.
Incorrect irrigation in arid regions: causes a build up
of salt on the soil surface. This irrigation method is
commonly used in poor areas in which farmers uses
canal irrigation and other poor techniques because of
water shortage.
 Soil becomes less usable and easily be lost via erosion,
nutrients in the soil can be removed by wind or water, salt
can build up in the soil which makes it harder for plant
growth.
 Vegetation is Lacked or Damaged due to soil loss and
overgrazing.
 Famine: Places that have war and poverty are most likely to
have famine. Drought and poor land management
contribute to famine spreading.
 Food Loss: soil is not suited for growing food;
therefore the amount of food being made will decline.
If the population is growing, this will cause economic
problems and starvation.
 People near Affected Areas: Desertification can cause
flooding, poor water quality, dust storms, and
pollution. All of these effects can harm people living
near an affected region.