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The Changing Himalayas
The Imja lake lies at 5100 masl in the Khumbu region of Nepal. It formed and developed very rapidly in the second part of the 20
th
century
as the glacier retreated at a very high rate (maximum more than 70 m per year). Glacial lakes of this type need to be monitored closely as
the moraine dams can be unstable, and if they break can lead to an outburst flood.
might enjoy increases in net primary productivity (NPP), alpine steppes, known as ‘black bleaching’ (Ma and Wang
locally, the greatest confidence is in predicting implications 1999; Miller 2000). Qinghai Province in China alone has
for vegetation production, with lesser confidence in more than 20,000 km
2
of degraded rangeland.
implications for vegetation composition, animal production,
Upward movement of the tree line and encroachment of
and adaptation options (Campbell and Stafford Smith
woody vegetation on alpine meadows are reported widely.
2000). Climate change has been reported to impact on
In the eastern Himalayas, the tree line is rising at a rate
grassland productivity, ecosystems, and the distribution
of 5 to 10 m per decade (Baker and Moseley 2007). As
and composition of plant communities (Wilkes 2008).
temperature rises, species shift their ranges to follow their
Some rangelands might suffer from degradation due to the
principal habitats and climatic optima.
warmer and drier climate (Dirnbock et al. 2003). Degraded
rangeland already accounts for over 40% of dryland on
Increasing temperatures and water stress are expected
the Tibetan Plateau (Zhong et al. 2003; Gao et al. 2005);
to lead to a 30% decrease in crop yields in Central and
and it is expanding at a rate of 3 to 5% each year (Ma
South Asia by the mid-21
st
Century (UNDP 2006). At high
and Wang 1999). Increases in evaporation, reduction in
altitudes and latitudes, crop yields should increase because
snow cover, and fluctuations in precipitation are key factors
of reductions in frost and cold damage. It will be possible to
contributing to the degradation of dryland ecosystems.
grow rice and wheat at higher latitudes than is currently the
case in China.
The possibility of alterations in the overall albedo,
water balance, and surface energy balance in high-
Irrigated lowland agriculture, found in all of the large
altitude grasslands and the increasing degradation and
basins receiving their runoff from the Hindu Kush-Himalayan
desertification of arid areas is causing concern. Signs of
system, is projected to suffer negatively from lack of dry
the effects of climate change on grasslands have been
season water. Considering that the reported or projected
documented in the northeast Tibetan Plateau where Kobresia
glacial meltwater component amounts to, for example, 20
sedge and alpine turf communities are changing to semi-arid
to 40% in rivers in Western China (Tao et al. 2005), 50%
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