age would be greatly diminished in the Himalayas–Hindu Kush
78
. a rise in elevation of the snowline will lead to drying out of vil-
The extent and amount of snow will also decrease as tempera- lage grazing areas, eroding the basis of villagers’ livelihoods
tures increase and the snow line moves to higher elevations. by reducing the carrying capacity of their surrounding lands.
Given that some of the rivers, such as the Amu Darya and the Even slight increases in severity and frequency of land slides
Indus, receive nearly 90 per cent of their total water discharge and flash floods may significantly reduce the ability of herders
from upper mountain catchments including glaciers and snow
76
, to move and transport their livestock between grazing areas
the water flow in the rivers could decline perhaps by as much and to towns for sale.
as 70 per cent if the glaciers disappear. In some cases, like in
the Tien Shan, the rivers could become seasonal. Reduced water The hydrological role of mountains, glaciers and snow is par-
flow in the dry seasons will lead to more and longer periods with ticularly significant for the Tarim, Syr Darya, Amu Darya, Indus,
critical shortages of water for transportation, drinking water and Ganges, Brahmaputra, Yangtze and Huang He (Yellow) riv-
irrigation, with consequences for trade, small and large-scale ag- ers
74,76,81
(Table 1). With increases in seasonal floods and sig-
riculture
74
and with increased potential for disputes over sectoral nificantly reduced overall water flow, especially during critical
and regional allocations of this diminishing resource. times of low rainfall, about 1.3 billion people could be exposed
to risk of increased water shortages:
The impacts are not evenly distributed geographically or social- in China up to 516 million people;
ly. High proportions of impoverished populations in the region in India and Bangladesh approximately 526 million people;
are mountain and foothill dwellers
74,79,80
. Impoverished popula- in central Asia, including the Xinjiang province of China,
tions have also largely settled in areas with high flood risk, such about 49 million people;
as low-lying urban areas and deltas – because there is often in Northern India and Pakistan as many as 178 million people.
no alternative
74
. The impacts are aggravated by the methods of
meeting energy demands – traditional fuel sources such as fuel This only includes the populations living in the watersheds, not
wood and animal dung account for 94 per cent of energy supply those affected by reduced crop production from failure to se-
in some mountain areas in Nepal and Tibet
79
. Because of this cure water for irrigation, or those affected more generally from
dependence on fuel wood and livestock, most watersheds have impacts on regional and national economies
82
. The result of
experienced deforestation and overgrazing, making the hill- glacier loss is therefore not only direct threats to lives, but also
sides much more vulnerable to land slides, either during peak great risks of increased poverty, reduced trade and economic
snowmelt or in relation to tectonic activity
75
. Only 3 per cent of decline. This poses major political, environmental and social
watersheds in the region are protected. High in the mountains, challenge in the coming decades.
Basin Total % % % basin Hydrological significance of
River km
2
population cropland forest protected glaciers and snow for rivers
Tarim 1 152 000 8 067 000 2 <1 21 Very high
Syr Darya 763 000 20 591 000 22 2.4 1.0 Very high
Amu Darya 535 000 20 855 000 22 0.1 0.7 Very high
Indus 1 082 000 178 483 000 30 0.4 4.4 Very high
Ganges 1 016 000 407 466 000 72 4.2 5.6 High
Brahmaputra 651 000 118 543 000 29 19 3.7 High
Yangtze 1 722 000 368 549 000 48 6.3 1.7 High
Huang He (Yellow river) 945 000 147 415 000 30 1.5 1.3 High
Salween 272 000 5 982 000 6 43 2.2 Moderate
Mekong 806 000 57 198 000 38 42 5.4 Moderate
Table 1: An overview of the major rivers in the Himalayas-Hindu Kush-Tien Shan-Tibet region.
Source: Viviroli and others 2003
76
; IUCN/WRI 2003
81
; UNEP 2004
74
CHAPTER 6B GLACIERS AND ICE CAPS 131