Geoscience Reference
In-Depth Information
24
Desertification: causes, consequences and solutions
The wind grew stronger. The rain crust broke and the dust lifted up
out of the fields and drove gray plumes into the air like sluggish
smoke. . . . The finest dust did not settle back to earth now, but
disappeared into the darkening sky.
All day the dust sifted down from the sky, and the next day it sifted
down. An even blanket covered the earth. It settled on the corn,
piled up on top of fence posts, piled up on the wires; it settled
on roofs, blanketed the weeds and trees.
John Steinbeck (1902-1968)
The Grapes of Wrath
(1939)
24.1 Introduction
In the quotation cited at the head of
Chapter 23
, Aldo Leopold (
1949
) commented
that: 'The effort to control the health of land has not been very successful. It is now
generally understood that when soil loses fertility, or washes away faster than it forms,
and when water systems exhibit abnormal floods and shortages, the land is sick'. He
was referring very clearly to what we now call desertification. He went on to argue
that 'the fallacy the economic determinists have tied around our collective neck, and
which we now need to cast off, is the belief that economics determines
all
land use'.
Desertification is an elusive concept and has proved very hard to define. The pro-
cesses leading to desertification have been widely debated, often without satisfactory
resolution. One reason for this lack of accord has been a polarisation of the debate,
with one side claiming human activities as
the
cause of desertification and the other
claiming that climate was the primary cause of desert expansion into hitherto unaf-
fected areas. In order to understand the reasons behind the international adoption of the
current definition, it will be useful to examine the history of this debate (Grove,
1974
;
Darkoh,
1989
; Warren and Khogali,
1992
; Mainguet,
1994
; Thomas and Middleton,
473
