World’s Soil Resources

Figure 10.2 Threats to soils in the Asia region by country.
10.3 | General threats to soils in the region
10.3.1 | Erosion by wind and water
Soil erosion is the most important threat to soil in Asia. Water erosion by rainfall and surface water flow is
dominant in humid regions with torrential rains, as in South and East Asia. In drier or desert areas, wind is the
driving force inducing soil erosion. This threat is discussed below in Section 10.4.1 in detail.
10.3.2 | Soil organic carbon change
Data for evaluating soil organic carbon (SOC) change in Asian countries are limited because countries do
not generally monitor SOC stock and changes. However, data from available literature show that where there
are increases in crop yield in croplands of East and Southeast Asia, SOC is retained. SOC has also been shown
to accumulate in forest areas. However, in South Asia SOC is decreasing. This is because crop residues are
widely used as fuel and fodder and are not returned to the soil. In Indonesia, three anthropogenic activities
– deforestation, poor land management, and intensive cropping – contribute to SOC change in mineral and
peat soils (Section 10.5.2). Throughout the region, the degradation of grassland has generally caused great
losses of SOC stock. This threat is discussed in detail below in Section 10.4.2.
10.3.3 | Soil contamination
Sources of contamination of arable land in most Asian countries include (i) parent material, (ii) mining,
(iii) smelting, (iv) agrochemicals and sewage sludge applications, and (v) livestock manure uses (Luo et
al., 2009). There is an urgent need to reduce hazardous chemical concentrations of Cd, As, Pb, Cu and Zn,
especially in paddy soil and rice grains. In many regions of Southeast Asia (Bangladesh, India, China, Vietnam,
Taiwan - Province of China, Thailand and Nepal), arsenic is naturally present in groundwater and represents
a threat to sustainable agriculture (Smedley, 2003; Brammer and Ravenscroft, 2009). This enrichment is
Status of the World’s Soil Resources | Main Report Regional Assessment of Soil Changes
291
in Asia