Glaciers are shrinking fastest in Alaska and Patagonia in South America states a new report from the UN Environment Programme (UNEP), thinning by 35 and 25 m since 1960. Almost half the world's population depends on rivers that originate in glaciers and snow.

Communities living in dry areas of the world that depend on seasonal glacial meltwater will be affected first. Countries in Central Asia, Chile, Argentina and Peru all have low rainfall and precipitation and depend on glaciers for vital drinking water. Glaciers may take centuries to melt fully, but lower lying, smaller glaciers, many of which are critical water sources are disappearing fastest. Warmer average temperatures due to climate change are the main reason for the increased melting, though black soot deposits on ice is probably also contributing through increased absorption of heat. Glacial melt is expected to contribute between 40mm and 150mm (depends on the model used) to sea level rise by the end of the century.

"When glaciers disappear, people, livestock, birds and animals will be forced to move," says Christian Nellemann of the UNEP/GRID-Arendal research centre in Norway. "But ironically, a lot of people die in deserts also from drowning, when increasingly unpredictable rains cause flash floods." Other hazards are Glacial Lake Outburst Floods where trapped meltwater breaks out catastrophically, releasing up to millions of tonnes of water into rivers and valleys below. Following increased glacial melting since 1980, these floods are on the increase in South America, China, Nepal and Bhutan. Five major events took place in Patagonia alone in 2008 and 2009, releasing 200 million tonnes of water each time into the Colonia river killing livestock and damaging farms.

Not all glaciers are shrinking worldwide, a few are growing due to changes in snow and rainfall patterns, those in Western Norway and on the South Island of New Zealand are benefitting.

Coincident with the release of the report, the Norwegian environment minister Erik Solheim announced 12 million dollar funding over five years to help communities in India, Pakistan and China adapt to the changes in the glaciers on which they depend.