Agriculture Reference
In-Depth Information
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the Food and Agriculture Organization (FAO) of the United Nations de-
veloped a methodology for assessing soil degradation with detailed criteria
for each type of biophysical degradation. Subsequently, FAO conducted a
Global Assessment of Progress on Desertification in 1984 and 1992. The
global estimate of land degradation or desertification ranged from 2001
million ha in 1984 to 3475 million ha in 1992 (i.e., 13-23% of the earth's
surface; FAO, 1979, 1995).
G lobal Assessment
In 1987 the United Nations Environment Programme (UNEP) requested
an expert panel to produce, in the shortest time possible, a scientifically
credible method to assess soil degradation at the global scale. The first
Global Assessment of Soil Degradation (GLASOD) in the early 1990s
provided a systematic qualitative assessment of the extent and severity of
land degradation, and its results formed the basis for the World Atlas of
Desertification at a scale of 1:10 million (UNEP, 1992, 1997). This map is
based on input from more than 250 soil scientists in the 21 regions dividing
the world. This expert assessment method used a mapping base, a set of
semiquantitative definitions for soil degradation, case studies, and a team
of national and international experts.
GLASOD is criticized today as inaccurate, subjective, and not appro-
priate for assessing soil degradation at the country level. Most of the indi-
cators used in the GLASOD were biophysical and not socioeconomic and
therefore did not include the institutional and policy driving forces of land
degradation. Despite these drawbacks, GLASOD remains the only global
database on the status of human-induced soil degradation, and no other
data set comes as close to defining the extent of desertification at the global
scale (UNEP, 1997). In another approach, Dregne et al. (1991) used results
of vegetation degradation estimates for comparison with soil degradation.
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A ssessment of South and Southeast Asia
In response to requests for more detailed information on soil degradation,
in 1993 the Asia Network on Problem Soils (www.isric.nl) recommended
preparation of a soil degradation assessment for South and Southeast Asia
(ASSOD) at a scale of 1:5 million. The methodology of this assessment
reflects comments from the peer review of GLASOD. As a result, ASSOD
has a more objective cartographic base and uses the internationally en-
dorsed World Soils and Terrain Digital Database (SOTER) to delineate
mapping units (Oldeman, 1988; see also www.isric.nl). Like GLASOD,
ASSOD focuses on displacement of soil material by water or wind and in
situ deterioration of soil by physical, chemical, and biological processes.
ASSOD, however, places more emphasis on trends of degradation and the
effects of degradation on productivity.
Although an improvement over GLASOD, ASSOD is not without prob-
 
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