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).
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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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