The Economics of Desertification, Land Degradation, and Drought

that the yields of salt-tolerant wheat, barley, and sorghum varieties could be 50 percent
higher than the yields of conventional varieties (Ranjbar et al. 2008).
3. Use of halophytic plants for economic purposes: Related to (ii), the use of halophytic, or
salt-loving, plants (such as date, palm, barley, and cotton) could help reduce salinity
(Natchergaele et al. 2010). Areas with saline soils could be used to grow halophytic crops
and fodder (Toderich et al. 2009).
4. Remediation of saline soils by leaching soluble salts below the root zone: This practice
(Qadir et al. 2006) requires a large amount of water and may not be amenable to areas
with limited irrigation water—a common phenomenon in dry areas, where salinity is
common. The practice also requires soils with good porosity and a deeper water table to
allow efficient leaching. In areas with poor porosity or a shallow water table, soaking the
soils and later draining saline water out of the farming area has been done. Mechanical
removal of salt crusts has also been used; however, this practice is limited, because it can
only remove the crusts on the surface.
Past studies have compared two leaching methods: continuous ponding and intermittent
ponding (Qadir et al. 2006). Intermittent ponding (leaching) reduces the water requirement by about
one-third the amount required for continuous ponding to remove about 70 percent of soluble salts
(Hoffman 1986); however, leaching requires more labor than continuous ponding (Oster 1972). In
addition, intermittent leaching combined with mulching reduced evapotranspiration and further
improved salt (Carter et al. 1964).
Compaction
Compaction is a major problem in areas with high livestock population density and in areas where
heavy machinery is used for cultivation. Compaction due to livestock pressure is a severe problem in
the Sahelian region, the horn of Africa, Central Asia, northeastern Australia, Pakistan, and
Afghanistan (Nachtergaele et al. 2010). Compaction due to the use of heavy machinery is severe in
the United States, Europe, South America, India, and China (Nachtergaele et al. 2010).
An experiment in Pakistan showed that soil compaction reduced up to 38 percent of wheat
yield, largely due to its impact on water and nutrient use efficiencies (Ishaq et al. 2001). Practices
used to address compaction include periodic deep tillage and the recently popular conservation
agriculture, which uses minimum or zero tillage, control of soil erosion, and water and moisture
conservation through the use of crop residues such as mulch, cover crops, and crop rotation (Hobbs
2007). The adoption rate of conservation agriculture is estimated to be about 95 million hectares,
which is about 6 percent of the global crop area of 1,527 million hectares (FAOSTAT 2008).
However, adoption of conservation agriculture remains limited in developing countries. The United
States, Brazil, and Argentina account for 71 percent of the total land area under conservation
agriculture (Derpsch 2005).
Reduction of livestock density is one of the methods used to address this problem; however, it
has not been successful due to the top-down approach used to implement it (Mwangi and Ostrom
2009; Nori et al. 2008). Therefore, appropriate measures, such as periodic deep plowing, controlled
traffic, conservation tillage, and the incorporation of crops with deep tap root systems into the rotation
cycle, are necessary to minimize the risks of subsoil compaction.
Loss of Biodiversity
A recent study on The Economics of Ecosystems and Biodiversity (TEEB) showed that the share of
mean species abundance (MSA) in 2000 was below 60 percent of its potential in much of India,
northeastern and midwestern United States, northeastern Brazil, India, China, Europe, the Sahelian
zone, and Central Asia (TEEB 2010). TEEB predicted that by 2050, the total global loss of MSA
would be 15 percent of its 2000 level and that other losses would largely results from managed
forests, agricultural areas, natural areas, and grazing areas (Figure 5.1). These losses would mainly
result from climate change, infrastructure development, pollution, expansion of agricultural areas, and
fragmentation (Figure 5.2).
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