The turning into a desert is a natural phenomenon or not which originates in of the climatic variations and/or the consequences of human activities. This word describes a local aridification, or the projection of the Désert towards the nondesert grounds before.
It is a process of impoverishment of the soil which can take place outside a desert; in zones Arid S, semi-arid and subhumides dry.
This phenomenon represents one of the Natural disaster in the long run. The turning into a desert is amplified by the warming of the planet and by the Surpâturage (with the the Sahel in particular).
The turning into a desert as recognized for one half-century has become extensive increasing and considered to be rather worrying so that UNO at the Top of the ground of RIO in June 1992 (Conference of the United Nations on the environment and the development (Cnued)) considered to be useful to propose a world convention on the fight against the turning into a desert. For lack of agreement of the elected officials on his contents, it became a declaration of intent.
The turning into a desert is an obstacle with the development of agriculture, and the rise in the standard of living of the populations of the zones concerned.
Difficulty of measurement
According to calculations, the percentages of surfaces touched by the turning into a desert in the arid regions vary from 19,5% (if one measures only the impoverishment of the soil) with 69,5% (by measuring the degradation of the vegetation).
Figures, and areas of the world touched
UNESCO estimates that a third of emerged surfaces of planet is threatened by this phenomenon.CIRAD estimates, him, that 40% (or 5,2 billion hectares on 13 billion) of the emerged grounds are it). The width of the damage is more visible in the countries of the South, but locally of the phenomena of turning into a desert are noted in north of the Mediterranean and in Central Asia. 37% of the arid regions are African, 33% are Asian and 14% relate to Australia. The southernmost America and fringes (Spain, Italy, Crete, Greece, etc) undergo also phenomena of aridifications local but serious. For the CIRAD, in the year 2000,3,6 billion hectares (70%) of the arid grounds was already in the course of turning into a desert, 93% was or is still grazed, against 6% cultivated without Irrigation and 1% with irrigation.
For IUCN, it is with the beginning of the year 2000,70% of the arid grounds undergo a process of turning into a desert (25%de emerged grounds, and 1/6 of the world population; that is to say 900 million people living in 90 countries).
Africa and the Sahara
Certain desert areas of the the Sahara were green and wet only a few millenia ago, this is attested by cave paintings.Many efforts carried out since the years 1970 to install a green belt to block the projection of the Sahara towards north and the south showed failures. Various efforts specifically related to Africa, with
- in 1968: the Convention of Algiers is adopted by the Member States of the O.U.A (Organization of African Unity).
- in 1974: General meeting of the United Nations.
- in 1984: a Conference of the United Nations is devoted to the turning into a desert (Nairobi, Kenya) and creates an action plan to fight the turning into a desert (P.A.C.D)
- 1984: The Lome Convention (Togo).
- 1994: a “international convention on the fight against the turning into a desert” meets in Paris.
Australia
The turning into a desert threatens several areas of the center of Autralie: the extensive breeding of sheep and bovines poses problem during the years of dryness. It causes the overgrazing and the disappearance of the grounds. The erosion tends consequently to increase: the turning into a desert in Australia is the product of factors anthropic and natural
Mongolia
The turning into a desert touches 140.000 km ² in Mongolia. It is estimated that 683 rivers were drained recently and precipitations show a fall of 10% compared to the average of the Années 1940
See too
To see
The World Atlas off Turning into a desert (1992), prepared by the PNUE, draws up an assessment of the intensity and the extent of the turning into a desert in the World. The World atlas off turning into a desert of 1997 (2nd edition UNEP), of Middleton, Oct. 1997,192p. 27.5x37 produced an update confirming the projection of the deserts and the turning into a desert.
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