The Economics of Desertification, Land Degradation, and Drought

those that affect economic plant yields, similar to those used for the 1983 assessment. Results indicate
70 percent land degradation of the assessed land. Although estimates are considerably better than the
1983 estimates, the database and information upon which calculations were made were still poor, with
an upward bias.
Global Assessment of Human-Induced Soil Degradation by the International Soil
Reference and Information Centre (1987–1990)
The Global Assessment of Human-Induced Land Degradation (GLASOD) study, which was carried
out by the World Soil Information Center and commissioned by the United Nations Environment
Program (UNEP) between 1987 and 1995, was the first major global assessment of soil degradation.
The project represented “the basis of the most recent UN studies of global land degradation and
desertification” (Thomas and Middleton 1996: 119). Within three years (by 1990), GLASOD
developed a world map of human-induced soil degradation (Oldeman, Hakkeling, and Sombroek
1991b). The approach defines soil degradation as “human-induced phenomena, which lower the
current and/or future capacity of the soil to support human life” (UNEP 1997b). The map was
originally produced for the United Nations Conference on Environment and Development (UNCED)
in 1992.
The GLASOD project was conducted using expert opinions of about 250 experts drawn from
21 regions of the world (Nachtergaele et al. 2010). Soil degradation was mapped by types and by
country using the following degradation attributes: soil erosion by wind and water, chemical soil
deterioration, and physical soil deterioration (for further explanation of types of degradation, see
“Types of Land Degradation” in Section 3). The authors then identified different degrees as light,
moderate, severe, and very severe land degradation (Oldeman, Hakkeling, and Sombroek 1991a). The
study observed that 38 percent of the global land area affected by human-induced land degradation
was lightly degraded, 46 percent was moderately degraded and 15 percent was strongly degraded
Oldeman 1998). Water erosion was identified as the most important form of soil degradation,
followed by wind erosion, both of which accounted for about 84 percent of land area degraded (Table
2.1 and Figure 2.1). The most degraded area was Europe (25 percent), followed by Asia (18 percent)
and Africa (16 percent); North America reported the smallest area degraded.
Table 2.1—GLASOD (1991) extent of human-induced soil degradation (in million hectares)
Type of land
degradation World Asia
West
Asia Africa
Latin
American
Countries
13
North
America
Australia
and
Pacific Europe
% of
total
Water erosion 1,094 440 84 227 169 60 83 115 55.70
Wind erosion
Nutrient
548 222 145 187 47 35 16 42 27.90
depletion 135 15 6 45 72 - + 3 6.87
Salinity 76 53 47 15 4 - 1 4 3.87
Contamination 22 2 + + + - - 19 1.12
Physical 79 12 4 18 13 1 2 36 4.02
Other 10 3 1 2 1 - 1 2 0.51
Total 1,964 747
38.0
287 494 306 96 103 218 100.00
% of total
3 14.61 25.15 15.58 4.89 5.24 11.10
Source: Oldeman, Hakkeling, and Sombroek 1991a.
Notes: + means increasing land degradation; - means decreasing land degradation.
The GLASOD study was useful in formulating a number of global conventions and
international and national land management development programs. GLASOD has also been quite
useful in raising the attention of the extent and severity of soil degradation.