(CNN) -- On the steep, dusty slopes of the Chacaltaya mountains, thousands of meters above sea level in the Bolivian Andes, the hardy farmers tending root crops or herding llamas have no need of scientists or climatologists to measure the impact of global warming.

For as long as anyone can remember, communities such as the village of Botijlaca have relied on melting ice flowing down from the Chacaltaya glacier as a source of drinking water, to irrigate their crops and water their animals.

Now the 18,000-year-old glacier -- once home to the world's highest ski resort -- has almost disappeared, reduced to a slither of snow and ice in the space of a few decades. Researchers say Chacaltaya has lost around 80 percent of its volume in just 20 years.

"There is less water now," says Leucadia Quispe, a 60-year-old mother, grandmother and potato farmer. Seven of her eight children have left the region, she says, because there is no way for them to make a living. Most of the men of the village have also gone, heading to the conjoined urban sprawl of nearby La Paz and El Alto in search of work, returning just once or twice a month to see their wives and families.

Each day Quispe spends hours hauling two five-litre containers of water by hand from a nearby river. "We used to be able to get water for irrigation from the streams that came down from the glacier. But the streams are no longer there, so now we supplement the water from a river further up in the valley," she explains.

Jaime Nadal, the United Nations Population Fund's (UNFPA) representative in Bolivia, said that Quispe's situation was far from unusual. "Young people tend to leave these areas. Old women are typically left in the community having to perform harder and harder tasks to keep up the household. We already see mostly old women in many of these communities."

In a report released on Wednesday, UNFPA warns that it is women in the developing world such as Quispe who are bearing the brunt of the worsening and accelerating impact of climate change.

"Women are on the front lines of many societies buffeted by climate change -- and research indicates they tend to be more vulnerable to these impacts," said the report's lead author, Robert Engelman.

According to the report, women in poorer societies are most at risk because they make up a larger share of the agricultural workforce and have fewer income-earning opportunities. They also shoulder the burden of caring for other family members and household management, limiting their mobility and trapping them in a cycle of deprivation, poverty and inequality.

"For many people, especially poor women in poor countries, climate change is here and now," said UNFPA Executive Director Thoraya Ahmed Obaid. "Poor women in poor countries are among the hardest hit by climate change even though they contributed the least to it."

Quispe and women like her may be at the sharp end of environmental change but they will not be suffering in isolation for long. In Bolivia, the disappearance of the glaciers -- the mountain's "white ponchos" in the words of President Evo Morales -- has profound implications for the Andean nation water and energy supplies.

Glacial melt provides 15 percent of La Paz's drinking water and 40 percent of the country's energy comes from hydroelectric sources, according to an Oxfam report released earlier this month. Yet in 2000, South America's poorest country contributed just 0.35 percent of the world's carbon emissions, Oxfam said.

"We are losing something that is a human right, a source of life -- water for drinking, for food, for the animals, for electricity," said Bolivian climate change expert Jose Gutierrez.

But if the world's poor -- and women in particular -- are already paying a disproportionate price for the vast quantities of carbon pumped into the atmosphere by industrialized societies, UNFPA argues that they can also play an important role in helping to mitigate the potentially "catastrophic" consequences of global warming.

According to the report, universal access to reproductive healthcare and family planning -- a UNFPA goal since 1994 -- in combination with improved education of girls and gender equality would lead to significant declines in fertility, stabilizing the population of the planet at a level far below estimates commonly used in scientific models of future climate change.

In turn, the argument goes, carbon emissions would also fall, reducing the risk of global warming reaching a "tipping point" and running out of control.

"Helping women to make their own decisions about family size would protect their health, make their lives easier, help put their countries on a sustainable path towards development -- and ensure lower greenhouse-gas emissions in the long run," said Obaid.

But critics said that conflating population control with efforts to tackle climate change was overly simplistic. Caroline Boin, an analyst at London-based think tank International Policy Network, also said the report was patronizing to women in the developing world.

"Whatever the problem, UNFPA repeats the same old mantra -- the culprit is population and the solution is condoms," she said. "Food scarcity, water shortages, and health problems in poor countries truly are threats for women. Population and climate control policies are not the solution, and if anything, will give governments an excuse to remain complacent in addressing poverty."

But Obaid said the debate over tackling climate change needed to take into consideration "how individual behavior can undermine or contribute to the global effort to cool our warming world," especially in the run-up to December's COP15 summit in Copenhagen.

"We cannot successfully confront climate change if we neglect the needs, rights and potential of half the people on our planet," she said.

"Women should be part of any agreement on climate change -- not as an afterthought or because it's politically correct, but because it's the right thing to do. Our future as humanity depends on unleashing the full potential of all human beings, and the full capacity of women, to bring about change."