Agriculture Reference
In-Depth Information
al., 2003). Degraded rangeland already accounts for over 40 percent of
dryland on the Tibetan Plateau (Gao et al., 2003); and it is expanding at a
rate of 3 to 5 percent each year (Ma and Wang, 1999). Increases in evapo-
ration, reduction in snow cover, and fluctuations in precipitation are key
factors contributing to the degradation of dryland ecosystems.
The possibility of alterations in the overall albedo, water balance and
surface energy balance in high-altitude grasslands and the increasing
degradation and desertification of arid areas is causing concern. Signs of
the effects of climate change on grasslands have been documented in the
north-east Tibetan Plateau where
Kobresia
sedge and alpine turf commu-
nities are changing to semiarid alpine steppes, known as 'black bleaching'
(Ma and Wang, 1999; Miller, 2000). Upward movement of the tree line
and encroachment of woody vegetation on alpine meadows are reported
widely. In the eastern Himalayas, the tree line is rising at a rate of 5 to 10 m
per decade (Baker and Moseley, 2007). As temperature rises, species shift
their ranges to follow their principal habitats and climatic optima. Increas-
ing temperatures and water stress are expected to lead to a 30% decrease
in crop yields in Central and South Asia by the mid-twenty-first century
(UNDP, 2008). At high altitudes and latitudes, crop yields should increase
because of reductions in frost and cold damage. It will be possible to grow
rice and wheat at higher latitudes than is currently the case in China.
Irrigated lowland agriculture found in all of the large basins receiving
their runoff from the Hindu Kush-Himalayan system, is projected to suffer
negatively from lack of dry season water. Considering that the reported
or projected glacial melt water component amounts to, for example, 20
to 40% in rivers in Western China (Tao et al., 2005), 50% or more in
the Indus (Tarar, 1982) and 30% in the major rivers in Nepal during the
premonsoon season (Sharma, 1993), the implications of dry season wa-
ter stress are likely to be massive. In addition, an increase in agricultural
water demand by 6 to 10% or more is projected for every 1 °C rise in
temperature (IPCC, 2007a). As a result, the net cereal production in South
Asian countries is projected to decline by at least between 4 to 10% by
the end of this century, under the most conservative climate production
projections (IPCC, 2007a).
