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8/14/2019 -University of Alexandria Faculty of Agriculture Saba-Pasha

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byby::

Jamal suliman elgosniJamal suliman elgosni

Under supervision of. Prof. Dr: Maher George NasseemUnder supervision of. Prof. Dr: Maher George Nasseem

University of AlexandriaUniversity of Alexandria--

Faculty of agricultureFaculty of agriculture

Saba-pashaSaba-pasha


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IntroductionLand degradation and desertification are

major environmental issues and a globalenvironmental problem it will remain animportant global issue for the 21st Centurybecause of its adverse impact on ruralproductivity and the environment, and itseffect on food security and the quality of life.Land degradation is a serious economic,

social problem related to environment, whichfaces many nations in the Region.


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DesertificationDesertification isisland degradation inland degradation in

arid, semi-arid and dry sub-humid areasarid, semi-arid and dry sub-humid areas

resulting from various factors, includingresulting from various factors, includingclimate variation and human activities"climate variation and human activities"

(UNCCD 1995)(UNCCD 1995)

What mean byDesertificationDesertification?

Desertification can be described as theBiological or Economic Loss ofProductivity and Complexity in

Croplands, Pastures and Woodland.


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WHAT MEANS LAND DEGRADATION? " land degradation" means reduction or loss, in

arid, semi-arid and dry sub-humid areas, of the

biological or economic productivity andcomplexity of rain fed cropland, irrigated cropland, or range , pasture, forest and woodlandsresulting from land uses or from a process orcombination of processes, including processesarising from human activities and habitation

patterns, such as:

i) soil erosion caused by wind and/or water;ii) deterioration of the physical, chemical andbiological or economic properties of soil; and

iii) long-term loss of natural vegetation


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Aridity Map

UNEP World Atlas of Desertification, 1997

Hyper-arid

Arid

Semi-aridDry sub-humid


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Desertification worldwide: Desertification affects over 40% of total land

area of the world:1.Africa: Two thirds of the continent is dry

lands. 73 % of its dry lands are moderately orseverely affected.

2.Asia: The largest amount of land affectedabout 1.7 B hectares. One third of the entirearea is dry lands 71% of its dry lands are

affected, All Pacific islands states face landdegradation deforestation, soil erosion,botany degradation, drought disasterand

fresh water shortage


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3. North America has the highest proportion of dry land 74%

4.Five of European Unions countries areaffected;

5.110countries have dry lands that arepotentially at risk.

Desertification costs annually the worldUS$42 Billion;

Over 250 million 250 million people aredirectly affected and one billion are underthreats or at risk.


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Causes of Desertification

Overgrazing

Deforestation

Precarious agriculture

Uncertain rainfall

River flooding

Depletion of surface waterDepletion of ground water


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too many livestock on too little land; removal ofcropresidues for feed/construction use; deforestationfor fuel wood and construction materials; andinappropriate irrigation practices that lead tosalinity.

DroughtThe threat ofdroughtconstantlylooms over dry land agriculture. Droughtdepletes vegetative cover and may lead tohuman actions, such as overgrazingandthe expansion of farmlands, that propel dry

lands more rapidly towards a desert likecondition. Increasing agricultural pressureon the land due topopulation growth alsoaggravates this downward spiral (Akhtar-Schuster et al. 2000).


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Climate changeis a major new threat (Hilleland Rosenzweig 2002). Modeling results

suggest that dry areas could become hotterand drier, especially semi-arid Africa andSouth Asia (Parry 2002). If climate changeincreases the frequency and/or intensity ofdroughts, it would aggravate desertification.Given the uncertainty in the models, otheroutcomes are also possible; recent

observations suggest that the Sahel is re-greening (UNEP 2003), although the reasonsare not understood and it appears that more

factors than just rainfall are involved.


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ore peop e cause more ry andegradation

some researchers are finding that

increasing populations lead to landrehabilitation if conditions are right.theynoted that as populations increase, thedemand for food also increases - creatingmore remunerative opportunities for

productive agriculture - and thereforeincentives for farmers to invest more in their

lands. Tiffen (2002) and Kabor and Reij(2004) describe cases where this ideaseems to be working, in places such asMachakos, Kenya, Gombe, Nigeria and

the Central Plateau of Burkina Faso.
http://www.oasisglobal.net/mar_kenya.htmhttp://www.oasisglobal.net/gombe.htmhttp://www.oasisglobal.net/burkina.htmhttp://www.oasisglobal.net/burkina.htmhttp://www.oasisglobal.net/gombe.htmhttp://www.oasisglobal.net/mar_kenya.htm


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Arid index,desertified land, human population andsheep number for last 5 decades in Northern China


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Wind tunnel experimental simulations on win

erosion rates


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Cleaver and Schreiber (1994) hypothesizedthat poverty, overpopulation and landdegradation create a self-reinforcing

downward spiral leading to ever-greatermisery and land degradation. Farmers maybe 'mining' their soils of nutrients andvegetative cover without replacing them,triggering soil erosion and productivitydecline - although the extent and importance

ofsoil mining is still an issue of debate.

Poverty and desertification
http://www.oasisglobal.net/soilmine.htmhttp://www.oasisglobal.net/soilmine.htm


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Approaches for CombatingDesertification

1.Weather forecast & early warning2.Water resources development/

management

3.Reforestation/afforestation

4.Land rehabilitation/soil

improvement5.Soil and water conservation


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Summary Desertification is a growing worldwide

problem that impacts a hugepercentage of the worlds population.

The economic cost of desertification is

in the many hundreds of billions ofdollars.

Desertification can be slowed and even

reversed by re -vegetation, waterconservation, livestock management andwise agricultural methods.


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Desertification in Algeria


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Desertification in Algeria

Desertification in Libya


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Desertification in Libya

Desertification in China


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Desertification in China


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