Andean glaciers are melting so fast that some are expected to disappear within 15-25 years, denying major cities water supplies and putting populations and food supplies at risk in Colombia, Peru, Chile, Venezuela, Ecuador, Argentina and Bolivia.

The Chacaltaya glacier in Bolivia, the source of fresh water for the cities of La Paz and El Alto, is expected to completely melt within 15 years if present trends continue. Mount Huascarán, Peru's most famous mountain, has lost 1,280 hectares (3,163 acres) of ice, around 40% of the area it covered only 30 years ago. The O'Higgins glacier in Chile has shrunk by nine miles in 100 years and Argentina's Upsala glacier is losing 14 metres (46ft) a year.

Although a few glaciers in southern Patagonia are increasing in size, almost all near the tropics are in rapid retreat. Some glaciers in Colombia are now less than 20% of the mass recorded in 1850 and Ecuador could lose half its most important glaciers within 20 years.

The rate of glacier retreat has shocked scientists, says a report on the effects of global warming in Latin America by 20 UK-based environment and development groups who have drawn on national scientific assessments. Their study says climate change is accelerating the deglaciation phenomenon.

"The speeding up of the ... process is a catastrophic danger," says Carmen Felipe, president of Peru's water management institute. In the short term, the president says, it could cause overflows of reservoirs and trigger mudslides, and in the longer term cut water supplies.

According to the Colombian institute of hydrology, back in 1983 the five major glaciers in El Cocuy national park were expected to last at least 300 years, but measurements taken last year suggest that they may all disappear within 25 years. Meanwhile, the ice sheet on the Ecuadorean volcano Cotopaxi and its glacier has shrunk by 30% since 1976.

"The [drastic melt] forces people to farm at higher altitudes to grow their crops, adding to deforestation, which in turn undermines water sources and leads to soil erosion and putting the survival of Andean cultures at risk," says the report by the Working Group on Climate Change and Development, which includes the International Institute for Environment and Development, Christian Aid, Cafod, WWF, Greenpeace and Progressio.

Their report, Up in Smoke, says snow and rainfall patterns in South America and the Caribbean are becoming less predictable and more extreme. "East of the Andes, rainfall has been increasing since about 1970, accompanied by more destructive, sudden deluges. Meanwhile, the last two hurricane seasons in the Caribbean rim have caused $12bn (£6.3bn) damage to countries other than the US. Tropical storms are expected to become more destructive as climate change intensifies. Climate change models predict more rainfall in eastern South America and less in central and southern Chile with a likelihood of greater and opposite extremes. The 2005 drought in the Amazon basin was probably the worst since records began."

Rises in sea level are expected to be especially severe in the region over the next 50 years, with 60 of Latin America's 77 largest cities located on the coast. The first hurricanes have recently hit south of the equator line in Brazil. "The net effect ... is to reduce the capacity of natural ecosystems to act as buffers against extreme weather."

"What we are seeing are many more negative and cumulative impacts. The larger the rate of [climate] change, the more the adverse effects predominate. Climate change is set to turn an already rough ride into an impossible one," says the report, which adds that the impact of climate change is "hugely" magnified by existing environmental abuse.

It proposes that Latin American governments do not repeat the mistakes made by past and present North American and European governments. Several countries in the region are proposing a new generation of mega dams which would displace thousands more people and destroy vast areas of the Brazilian Amazon. The new importance of soya, both as a food and biofuel crop, could also devastate the environment, leading to a battle for land between companies.

Large-scale coal, oil, and copper mining not only threaten fragile environments, says the report, but in some cases can physically endanger remaining glaciers and greatly increase climate changing emissions. "The Pascua Lama project on the borders of Chile and Argentina intends to move three glaciers that cover gold, silver and copper deposits. The glaciers sustain the mountain and valley ecosystems and there are fears that toxic wastes used in the mining will contaminate land and water," says the report.

Yesterday, the groups called on rich countries to urgently reduce greenhouse gas emissions and proposed that Latin America and the Caribbean governments be helped to reduce their vulnerability to extreme weather.

"The only option we have, apart from demanding that developed countries take responsibility for the damages that climate change is causing, is to try to neutralise the adverse impacts that are [already] upon us. It is time to rethink the model of international aid," said Juan Maldonado, former Colombian environment minister and president of the UN convention on biological diversity.

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"With each new flood, drought or hurricane in Latin America, precious gains in poverty reduction are lost. Extreme weather is set to cause massive loss of life in developing countries throughout the region. The international community must invest more in helping poor communities cope with the effect of climate change," said Paul Cook, head of policy for Tearfund.

The world's many thousands of glaciers have been stable or in slow retreat for more than 100 years but since around 1980 they have mostly been retreating drastically. The fastest decline is in the Himalayas, the Arctic, the Alps, the Rockies and the tropics. Most glaciologists believe this natural phenomenon is being accelerated by global warming. The effects of glacier melt are expected to be severe. Hundreds of millions of people in Asia and Latin America are dependent on glacier water. A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows to keep dams and reservoirs replenished. In Norway, the Alps, and the Pacific north-west, glacier runoff is important for hydropower. If all the ice on the polar icecaps were to melt, the oceans would rise an estimated 70 metres (230ft). But even a small melt will affect coastal life.