In Asia, more than 200 million people live in mountain and upland areas. The Himalayas contain the world’s third largest ice mass after Antarctica and Greenland. A 2003 study of glaciers and glacial lakes in Nepal and Bhutan by the International Centre for Integrated Mountain Development (ICIMOD) and UNEP identified 20 glacial lakes in Nepal and 24 glacial lakes in Bhutan as potentially dangerous in the event of a ‘glacial lake outburst flood’ (ICIMOD 2003). The formation of many glacial lakes on the glacier terminus is very likely the result of the remarkable retreat since the middle of the 20th century of glaciers in the Hindu Kush-Himalayan region, which may be related to climate change (UNEP RRC.AP 2003a) (see also GEO Indicators section). Nine glacial lakes in the Astor River basin in Pakistan and 24 in the Pumqu Basin of China Himalaya were also classified as potentially dangerous. Though no outburst has been recorded in the past decade, it is important to monitor the glacier lakes regularly in order to identify and design appropriate early warning and mitigation and response measures (ICIMOD 2003).