Soil Management for Sustaining Ecosystem Services - Principles of Sustainable Soil Management in Agroecosystems - page 524

by arid and semiarid climate, soil erosion by water is a serious problem during the
rainy season. Meshesha et al. (2012) analyzed soil erosion rates from 1973 to 2006.
Because of the decline in vegetation cover and deforestation, soil erosion rates
were 31 Mg/ha/year in 1973, 38 Mg/ha/year in 1985, and 56 Mg/ha/year in 2006.
Restoring degraded lands by installing exclosures and planted vegetation, and con-
structing stone bunds in cropland reduced erosion by 12.6% and 63.8%, respectively.
Identifying hot spots (erosion rate >20 Mg/ha/year) by integrated management is a
conservation-effective approach (Meshesha et al. 2012).
Projected climate change may lead to a more vigorous hydrological cycle and to
an increase in climatic erosivity of wind, rain, and runoff. An increase in frequency
of extreme events caused by the climate change is another factor. A simulation study
conducted in the Midwestern region of the United States indicated that relative to
1990-1999 as the baseline, erosion-related risks will increase by +10% to +310% for
runoff and +33% to +277% for soil loss (O'Neal et al. 2005). Wherever the rainfall
increases, erosion and runoff will increase drastically in the order of 1:1.7 (Nearing
et al. 2004). Reduction in vegetative cover in case of a decrease in rainfall would also
exacerbate soil erosion hazard in an uncertain and changing climate.
In addition to the adverse impacts on agronomic productivity and food security,
soil degradation by erosion also reduces biodiversity. Gilroy et al. (2008) linked
soil penetrability and SOC concentration (compaction) to the abundance of yellow
wagtails ( Motacilla flava) ) in arable fields. This link was the strongest during the lat-
ter part of the breeding season and indicated a significant relationship between soil
degradation and population decline. Soil erosion also affects the C dynamics and
the global C cycle (Lal 2005). It can be a major source of CO 2 and CH 4 , depending
on the site-specific pathways of C transported by erosion (Van Oost et al. 2007; Lal
2003).
There also exists a strong link between erosion and desertization. Removal of veg-
etative cover of trees by deforestation can affect water and energy balance. Further,
runoff harvesting practices become less effective with an increase in a site's aridity
(Safriel et al. 2011). Thus, effective erosion control through appropriate land use and
judicious soil management is essential to sustaining ESs.
19.4 SOIL DEGRADATION AND ESS
Principal global challenges facing humanity are food insecurity, abrupt climate
change with a high frequency of extreme events (e.g., drought in the United States
in 2012), scarcity of freshwater resources, and high energy demands for a rapidly
expanding world population. Soil degradation affects ESs both directly and indi-
rectly ( Figure 19.2 ). Direct effects include those on provisional, regulatory, and
aesthetical ESs. Indirect changes include adverse effects on water security, food
security, energy security, and soil security (Figure 19.2).
Food insecurity remains to be a major concern, especially in developing countries
of sub-Saharan Africa (SSA) and South Asia (SA). China is also facing a great chal-
lenge of increasing agronomic production. In China, the annual cereal production
must be increased to 600 Tg (Tg = 1 million Mg) by 2030 on a shrinking cropland
area and limited water resources (Miao et al. 2011). In SSA, 28% to 30% of the