Land Use, Land-Use Change and Forestry

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2.2.5.6. Degradation and Aggradation of Agricultural Lands

Prevention of degradation and restoration of degraded lands and soils are potentially important activities under the Protocol. Human-induced land and soil degradation occur in various types and degrees, as indicated by the United Nations Environment Programme's Global Assessment of Soil Degradation (GLASOD), a provisional geographical database and international scheme (Oldeman et al., 1991). This database-though based on country-level expert opinion only-has been used to conduct a global assessment of desertification (defined as land degradation-by human action or climate change-in arid, semi-arid, and dry subhumid areas) and is increasingly being applied and adapted for use at the national and regional levels (ASSOD, 1995, for Southeast Asia; Stolbovoi and Fischer, 1998, for the Russian Federation).

The GLASOD schema lists a variety of degradation processes, including water erosion (loss of topsoil, terrain deformation/ mass movement); wind erosion (loss of topsoil, terrain deformation, overblowing); chemical deterioration (loss of nutrients and/or organic matter, salinization, acidification, pollution with hydrocarbons or heavy metals); and physical deterioration (soil compaction, sealing, and crusting; water logging; subsidence of organic soils). Avoidance or amelioration of these processes has potential as Kyoto activities. Bergsma et al. (1996) provide detailed definitions of these degradation types, as well as measures for their control and reclamation. The degree of degradation is given in four classes: "light," "moderate," "strong," and "extreme." Reclamation of SOC content is relatively easy for the first two classes (see Section 4.4).

Soil improvement (aggradation) has taken place in many parts of the world. The World Overview of Soil Conservation Approaches and Technologies (WOCAT) (Liniger et al., 1988) gives spatial information on human-induced soil and land improvements for more sustainable agricultural land use, as well as the technologies applied. Restoration of SOM-depleted agricultural soils to near their original level appears to be a realistic opportunity, especially when terrain conditions permit mechanization of adapted cultivation practices (see Figure 2-4; Lal et al., 1998; Paustian et al., 1998; Batjes, 1999). Improvement of agricultural soils beyond the original level of soil organic matter, as a form of land and soil aggradation, may also be possible (Sombroek et al., 1993; Sandor and Eash, 1995; Bridges and de Bakker, 1997; Blume et al., 1998; Batjes, 1999; Gläser et al., 1999; McCann et al., 1999). The extra costs of such soil aggradation can become a feasible capital investment if collateral environmental and socioeconomic benefits are taken into account (e.g., control of desertification; increased security of food production; more sustainable agricultural settlement).

Figure 2-4: Conceptual model changes in ecosystem carbon stocks following disturbance or degradation, and mitigation through reclamation: (A) stabilization at lower stocks than original, (B) stabilization at original stocks, and (C) stabilization at higher stocks (after Johnson, 1995).



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