Perched in the centre of Asia’s ‘solid water reservoir’, Nepal is already feeling the effects and counting the costs of a changing environment. It’s a scene straight out of a tourist brochure: villagers in traditional dress walking down mountain paths between stone houses and ancient Buddhist stupas. Prayer flags flutter in the early autumn breeze. Behind, the Himalayas stretch to Tibet, their snowcapped peaks shining in the afternoon sun. But this scene is at the heart of one of the greatest environmental catastrophes of our time.

The Himalayan glaciers are melting faster than any others in the world. One is retreating by as much as 74 metres a year. Ten rivers, including the Mekong, Yangtze and Ganges, depend on the annual runoff from these snowcaps. Some scientists predict that a staggering number of people – 1.3 billion throughout Asia – will be affected as the rivers lose half their water flow over the next 30 years.

People in the postcard-perfect villages of the Himalayas are already feeling the impact. Global warming is playing havoc with weather patterns and traditional growing seasons. Farmers such as Wangal Tamang can no longer grow enough food. This year the father of 10 was able to harvest only enough to feed his family for two months.

The 2008-2009 growing season was one of the worst and driest in Nepal’s history. In a report last August, Oxfam International asked for food aid for 3.4m people. The organisation’s environmental assessment found that “the results were remarkably consistent with regional climate change projections, and deeply worrying”.

Poor crop yields, water shortages and extreme temperatures featured in the litany of problems. Average annual mean temperatures in Nepal increased by 0.06C between 1977 and 2000. According to the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD), by 2030 that will increase by an average of 1.4 degrees. Temperature increases are most pronounced high up in the Himalayas, where they are predicted to rise by 2 degrees.

In Dunche, community leader Lakpa Tamang explains how global warming is being felt in even the most mundane of ways. “Twenty years ago, this place was very cold,” he says. “Early in the morning we could not wash our face and we could not wash our body. But now, early in the morning the water is not as cold as before.”

Some villages face more immediate threats. Melted glaciers form lakes that burst their banks and cause massive and sudden floods. One of the worst incidents occurred on August 4, 1985, when the lake at the foot of the Langmoche glacier washed away a nearby village, along with bridges and a hydropower station. Five people died.

Some survivors moved to another valley, but their homes are now threatened by the Imja glacier, says Samjwal Bajracharya, a scientist at ICIMOD, which is melting at a faster rate than any other glacier it is monitoring. The earliest satellite photo was taken in 1962 and shows four “ponds” at the glacier’s foot, he says, adding that he makes the five-day trek there at least once a year to witness the phenomenon. With the Imja glacier retreating at 70 metres each year, scientists and villagers worry that the fast-growing lake could flood and wipe out communities in its path.

The expanding lake is one of 200 identified by ICIMOD as future dangers. The Nepalese government, Bajracharya adds, cannot afford “mitigation work” – namely, strengthening embankments to prevent them from overflowing. It’s an example of the bitter irony that global warming has brought to many developing countries –  it has one of the lowest carbon emission rates in the world, but is among the nations most affected by climate change.

“We need climate justice. There has been climate injustice from the developed countries to Nepal,” says Ganesh Shah, its former environment minister. “If you are making more emissions, you have to pay money for that and we can use it for adaptation, resettlement and new technology.”

For Nepal and other Himalayan countries, the threat posed by global warming has already become a reality. But as the glaciers continue to melt, other communities from Afghanistan to India, China to Cambodia will be forced to deal with the crisis.

Bajracharya calls the Himalayas a “solid water reservoir” for the people who depend on the rivers fed by the annual snowmelt for drinking, irrigating their fields and a multitude of other uses. Even in the face of such daunting data, he insists on being an optimist. “We have to face the problem and we should find the solution. We have to think about other aspects, too. This is a living planet, so in a living planet there is adaptation and new invention. We will always have some solution in the future.”

ICIMOD recommendations are aimed at water conservation and management, soil conservation and renewable energy, but they are costly and require richer countries to commit much more than they have offered to date. December’s Copenhagen Accord included a paltry $30 billion over the next three years to help developing nations reduce emissions and respond to global warming. It’s not enough.