Page 165 - Encyclopedia Of World History

desertification 515

A Mauri writing in the sand
the old name of Chinguetty:
Arbweir. This city was
founded in the tenth century
and is considered the seventh
holy city of Islam. Now the
city is completely buried by
sand.

ter estimates of its extent and rate of
increase can be made on the basis
of actual measurements” (Grainger
1990, 145).
The United Nations Environment
Programme (UNEP) has played a piv-
otal role in the promotion of deserti-
fication as an environmental issue, as
measured by reduced productivity of desirable plants, is made evident by this statement by Tolba and El-
undesirable alterations in the biomass [the amount of liv- Kholy: “Desertification is the main environmental prob-
ing matter] and the diversity of the micro and macro fauna lem of arid lands, which occupy more than 40 per cent
and flora, accelerated soil deterioration, and increased of the total global land area. At present, desertification
hazards for human occupancy” (Dregne 1986, 6–7). threatens about 3.6 billion hectares—70 percent of
Other experts admit the possible importance of natu- potentially dry lands, or nearly one-quarter of the total
ral climatic controls but give them a relatively lesser role. land area of the world. These figures exclude natural
Sabadell and associates define desertification as “the sus- hyper-arid deserts. About one sixth of the world’s pop-
tained decline and/or destruction of the biological pro- ulation is affected” (Tolba and El-Kholy 1992, 134).
ductivity of arid and semi arid lands caused by man made However, Thomas and Middleton have been critical
stresses, sometimes in conjunction with natural extreme of UNEP’s views on the amount of land that is deserti-
events. Such stresses, if continued or unchecked, over the fied. They state: “The bases for such data are at best
long term may lead to ecological degradation and ulti- inaccurate and at worst centered on nothing better
mately to desert-like conditions” (Sabadell, Risley, Jor- than guesswork. The advancing desert concept may
gensen, and Thornton 1982, 7). have been useful as a publicity tool but it is not one that
Other experts are more even-handed with respect to represents the real nature of desertification processes”
the balance of anthropogenic and natural causes.Warren (Thomas and Middleton 1994, 160).
and Maizels say: “A simple and graphic meaning of the
word ‘desertification’ is the development of desert like Rates of Desertification
landscapes in areas which were once green. Its practical Experts have conducted relatively few reliable studies of
meaning . . . is a sustained decline in the yield of useful the rate of desert advance. In 1975, Hugh Lamprey
crops from a dry area accompanying certain kinds of attempted to measure the shift of vegetation zones in the
environmental change, both natural and induced” (War- Sudan in Africa and concluded that that portion of the
ren and Maizels 1976, 1). Sahara Desert had advanced by 90 to 100 kilometers
Experts are not sure how extensive desertification is between 1958 and 1975, with an average rate of about
or how fast it is progressing. The lack of agreement on 5.5 kilometers per year. However, on the basis of analy-
the former process makes determining the latter diffi- sis of remotely sensed data and ground observations,
cult. As Grainger has remarked, “Desertification will Helldén (1984) found limited evidence that this ad-
remain an ephemeral concept to many people until bet- vance had taken place. One problem is that substantial