The Hindu Kush Himalayas – an arc of mountains stretching from Afghanistan, through Pakistan, China, India, Nepal, Bhutan, and Bangladesh, clear to Myanmar – are a gift to Asia, and the world. They are a well-known destination for those seeking adventure, spirituality, recreation, and biological and cultural diversity. However, as the source of ten major Asian rivers, the Hindu Kush Himalayas also act as the water towers of Asia, supplying vital water resources to over 1.3 billion people. These rivers not only provide freshwater to the region, they also feed the demands of a rapidly growing Asian population for energy and food. The plains of these great rivers – the breadbasket of Asia – feed over three billion people. Sustainably tapping the region's huge hydropower potential as a source of clean energy will also be increasingly important to fuel growing economies. However, there are disturbing signals coming from the mountains. And given Asia's high dependence on the mountains for water, energy, and food, there is reason for concern. Melting glaciers are a major signal of climate change in the Himalayas, as in other parts of the world. Mountain glaciers are shrinking, some quite rapidly in recent decades. Air pollution from the plains is finding its way up to the high mountains, leaving soot on white snowfields, causing increased melt in addition to affecting the health of local residents along its path. Given the importance of water to the region, knowing what will happen to glaciers and water supply is of critical importance. There are about 56,000 glaciers in the region containing about 6,000km 3 of water stored as ice – enough water to feed global annual irrigation water needs about two times over. The story of these glaciers, which has important implications for future water availability, is beginning to unfold as we collect more data. However, we still have large knowledge gaps to fill. Mountains also play a role in regulating monsoon patterns. With changes in temperature, how will monsoon patterns change, and what does this mean for future food and energy security? And how will people adapt to such changes? Initial research results suggest that over the next decades the amount of water reaching rivers will increase because of enhanced glacier and snow melt. However, after that the contribution from snow and glaciers will decrease, affecting communities in parts of the region, like the Indus River basin, that are heavily dependent on snow and glacier melt. Climate models also project an increase in annual precipitation and, in balance, the annual amount of flow may not change dramatically in other basins. In addition to uncertainty about future water availability, mountain communities are also experiencing trends of more intense rains and more drought periods, which may be of greater concern and require more immediate, short-term action than melting glaciers.
