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The Changing Himalayas
Rice terraces in China: water from the mountains irrigates agricultural land and contributes to increased food production
several more decades” (Barnett et al. 2005). Flooding may example, in the past three decades, on the Central Tibetan
also arise as a major development issue. It is projected that Plateau in the Kekexeli Wildland Area, the lower limit of
more variable, and increasingly direct, rainfall runoff will permafrost has risen by approximately 71 m, while the
also lead to more downstream flooding. sustained thickness has decreased by at least 20 cm (Wu et
al. 2001). Meanwhile, the extent of seasonal thawing has
intensified over large areas of permafrost causing increased
Permafrost
ground instability and erosion (Zhao et al. 2004), with
Areas in the high mountains and on the high plateaus
consequences such as the activation of the soil carbon pool
not covered in perennial snow and ice are underlain by
and northward expansion of shrubs and forests (Lawrence
permafrost. Permafrost areas will be sensitive to degradation
and Slater 2005). The disappearance of permafrost and
with climate warming. Recent studies show that the extent
expansion of non-permafrost will accelerate desertification
of permafrost is shrinking and that the active layer thickness
on the Tibetan Plateau (Ni 2000). Notwithstanding, there is
(the upper portion of soil that thaws each summer) is
almost no information about the full extent and behaviour of
increasing, and, further, that this has altered the hydrological
high mountain permafrost areas in the region.
cycle, vegetation composition, and carbon dioxide and
methane fluxes that appear linked to permafrost degradation
Water Related Hazards
(Lawrence and Slater 2005). The areas covered by
permafrost are much larger than those covered by glaciers According to the United Nations International Strategy
or perennial snow, especially in China. Permafrost plays for Disaster Reduction (UNISDR), in 2008, as in 2007,
a critical role in ecology, slope stability and erosion seven of the top ten natural disasters by number of deaths
processes, and surface water hydrology. On the Tibetan occurred in ICIMOD member countries (Afghanistan, China,
Plateau, the recent warming has been associated with India, Myanmar in 2008, Bangladesh, China, India,
decreasing areas of permafrost and a rise in the elevation Pakistan in 2007), accounting for 99% of the total deaths
of its lower altitude, as well as progressive thinning. For (82% in 2007). This indicates not only the prevalence of
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