The warning by the global conservation group on Monday comes as WWF releases a new report which it said exposes the rate of retreat of Himalayan glaciers accelerating as global warming increases.
  
The report indicates glaciers in the region - which represent the greatest concentration of ice on the planet after the Arctic poles - are now receding at an average rate of 10 to 15 metres per year.
  
"The rapid melting of Himalayan glaciers will first increase the volume of water in rivers, causing widespread flooding," Jennifer Morgan, director of the World Wide Fund for Nature's Global Climate Change Programme, said in a statement.
  
She added: "But in a few decades this situation will change and the water level in rivers will decline, meaning massive economic and environmental problems for people in western China, Nepal and northern India."
  
Climate change

Himalayan glaciers feed into seven of Asia's greatest rivers - the Ganges, Indus, Brahmaputra, Salween, Mekong, Yangtze and Yellow rivers - ensuring a year-round water supply to hundreds of millions of people in the Indian subcontinent and China. 
  

Seven of Asia's greatest rivers
feed off Himalayan glaciers

The WWF report was published in the run-up to two meetings in London on climate change organised by Britain as current head of the G8 group of industrialised nations.
  
The gatherings, a ministerial roundtable of the 20 largest energy using economies in the world, and then a G8 meeting of development and environment ministers focusing on climate change, take place from 15-18 March.
  
In a letter sent to participating ministers, WWF stressed the need to recognise climate change as an issue that seriously threatens security and development.
  
"Ministers should realise now that the world faces an economic and development catastrophe if the rate of global warming isn't reduced," Morgan said. 
  
Study details

A study commissioned by WWF shows that dangerous levels of climate change could be reached in just over 20 years and that if nothing is done, the earth will have warmed by two degrees Celsius above pre-industrial levels by some time between 2026 and 2060.
  
"All countries must understand that crossing the two degree Celsius ceiling is truly dangerous," Morgan said. 
  

"Water level in rivers will decline, meaning massive economic and environmental problems for people in western China, Nepal and northern India"

Jennifer Morgan,
Director of the World Wide Fund for Nature's Global Climate Change Programme

As glacier water flows dwindle, the energy potential of hydroelectric power will decrease, causing problems for industry, as well as agriculture, as reduced irrigation means lower crop yields, WWF said.
  
The environmental watchdog's report shows that three of Nepal's snow-fed rivers have shown declining discharge. Nepal has an annual average temperature rise of 0.06 degree Celsius per year.
  
In northwest China, the Qinghai Plateau's wetlands have seen declining lake water levels, lake shrinkage, an absence of water flow in rivers and streams, and a degradation of swamp wetlands, according to the report.
  
India's Gangotri glacier, which supports one of India's largest river basins, is likewise receding at an average rate of 23 metres per year.