The Fall of the Water

Intensified land use impacts water resources Intensified land use associated with exploitation, im- migration, population growth and resettlement along road corridors has major impacts on the water resources and their biodiversity (Dudgeon, 1992; 1995; 2000; Malmqvist and Rundle, 2002; Dudgeon, 2002). The processes are however very variable.

road corridors (Dudgeon, 1992; 1995; Zong and Chen, 2000; Du et al., 2001). This is particularly true also for abandoned agricultural terraces that are extremely sus- ceptible to erosion unlike well-managed terraces. This leads to increased waste and run-off into drainages and major rivers, including reduced capacity of watersheds to manage monsoon floods (Dudgeon, 1992; 1995; Col- lins and Jenkins, 1996; Zong and Chen, 2000; Du et al., 2001). The silt content increase and water quality becomes seriously reduced. Infrastructure development also facilitates increased im- migration. Growing land and population pressures lead to increasing settlement in flood-risk areas along lakes, behind former flood dikes, in drained wetlands and partly on steep slopes subject to land slides and erosion. Hence, when upland ability to retain floods is reduced and people simultaneously settle in flood prone areas, the human and environmental impacts of severe or even natural fluctuations in floods become serious. This is well known from the flooding of the Yangtze river which in part was attributed to deforestation and settlement patterns (Dudgeon, 1995; Zong and Chen, 2000; Du et al., 2001; Lu et al., 2003). China has invested large and also successful efforts in reducing deforestation in some of the catchments. Yet, as land use still intensifies in many regions, the high silt content resulting from erosion and the increasing water consumption for ir- rigation still remains a growing threat that will require further attention.

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Overexploitation of limited water resources is a grow- ing problem that is not easily solved in interior Asia. If climate change will result in less precipitation as snow or glacial recession, the impacts both on wildlife and human populations may become disastrous. Indeed, as more people have settled in areas prone to desertification even with natural cycles of expansion and contraction of the Taklamakan and Gobi deserts, the result is none the less critical for these people. However, also here human land use seems to play a primary role in aggravating the impacts of such cycles on both people and biodiversity (Liu and Sun, 2002; Lu et al., 2003)). Dust storms and blown sand represent an increasing problem for com- munication, health and transport in the region (Sun et al., 2000; Xuan and Sokolik, 2002). Vegetated hills, slopes, wetlands and forests are vital catchments for most rivers, and help purify water and reduce silt content in rivers by natural protection from erosion. With intensified land use along road corridors, forests are cut for firewood or intensified grazing results in overgrazing, deforestation and subsequent increase in erosion, flashfloods and land slides particularly along