Reducing rainfalls as well as general rising temperatures are increasing evaporation rates and thus releasing more carbon into the air. Wetlands only cover about 6% of the earth’s surface in terms of land but store an estimated 20% of the carbon.

More than 700 scientists are gathering at a major conference organised by the UN university and Brazil’s Universidade Federal de Mato Grosso to develop an action plan to protect the world’s wetlands.

Konrad Osterwalder, rector of the UN University, said that people in the past had viewed the habitats as a problem, which led to many being drained.

“Yet wetlands are essential to the planet’s health,” he explained. “With hindsight, the problems in reality have turned out to be the draining of wetlands and other ’solutions’ we humans devised.”

The conference will hear that global warming could be compounded if the draining of wetlands continues and release more carbon into the atmosphere. It’s estimated a drained swamp will release 40 tonnes of carbon each year per hectare drained and that in the past 100 years 60% of wetlands have been destroyed to provide fields for agriculture use.

“Wetlands act as sponges and their role as sources, reservoirs and regulators of water is largely underappreciated,” Professor Wolfgang Junk from the Max Planck Institute for Evolutionary Biology, Germany says.

“They also cleanse water of organic pollutants, prevent downstream flood inundations, protect river banks and seashores from erosion, recycle nutrients and capture sediment.”

The G5 countries made up of Mexico, Brazil, China, India and South Africa challenged the Group of Eight countries to cut their greenhouse gas emissions by more than 80% by 2050. The joint statement from the G5 developing nations said: “It is essential that developed countries take the lead in achieving ambitious and absolute greenhouse gas emission reductions.”

Environmental organisations have also called the 50% target “pathetic” and said more needs to be done to tackle climate change. The five nations also urged developed countries to commit to an interim target of a 25-40% cut below 1990 levels by 2020.

South Africa said the G8 statement was a “regression”, criticising the lack of firm targets to achieve sufficient cuts in emissions.

The G8 also voiced concern about soaring oil and food prices, and Zimbabwe, and pledged to speed up aid to Africa. But climate change has been one of the stickiest issues tackled at the summit in Toyako, northern Japan.

The five-page communique by the G8 – Britain, Canada, France, Germany, Italy, Japan, Russia and the US – repeats last year’s “vision” to reach the target of cutting emissions by at least 50% by 2050.

The EU had wanted the G8 to confirm that the 50% cut would be measured from 1990 levels of CO2 – as agreed under the Kyoto climate protocol.

But when the question was raised in a press conference Japanese Prime Minister Yasuo Fukuda said the cuts would be measured from “current levels”.