THERESA THOMPSON hears some of the world's experts debate the threats to the world's ecosystems - from the polar regions to the wetlands of Oxfordshire

Despite a poll showing that nearly a quarter of British adults were bored with eco news', Oxford-based environmental charity Earthwatch combats any idea of fatigue with lively and engaging discussion full of up-to-the-minute facts. This is the formula used in its annual public debates at the Royal Geographical Society in London. The latest, its seventh, chaired by Alistair Fothergill, co-director of the newly released film Earth, was called Precious Resources, Multiple Threats.

Five UK scientists, all leaders in their field, competed to win the 700-strong audience vote for which of the earth's ecosystems - forest, mountain, freshwater, marine or polar regions - is most under threat and urgently needs protection. It was hypothetical, of course, as was the trillion-dollar prize money up for grabs.

Prof Yadvinder Malhi, from the Oxford University Centre for the Environment, stated the case for forests. An expert in ecosystem science, he has worked in Oxford for three years on how forests, especially tropical, interact with the global climate.

"Forests are vastly important," said Prof Malhi. A half of all living species on the planet live in forest regions, especially the tropical rainforest. Forests absorb carbon dioxide and regulate the water cycles of the world. The canopy, the largest part of it, is so far mostly unexplored.

Prof Malhi believes them important for their spiritual value too.

"Whether tropical or the small wood on the edge of town, the size and immensity of trees affect us all - they are mystical, humbling," he continued, suggesting we each go into a wood that weekend, listen to its sounds, the birds, the leaves and learn to appreciate our woodlands.

In his view, climate change is not the major threat to forests - destruction is. He declared: "Destruction directly contributes to climate change. It's a cliché that deforestation is driven by poverty; much is driven by the large institutions, the palm oil plantations in Malaysia and Borneo for example, mechanised agriculture."

The real challenge is which is worth more? The soya bean pasture - or any other agriculture - or the rainforest? One is quantifiable and thus makes sense in our in global economy, one not. Slowing down the rate of deforestation can slow the rate of climate change, he argued. We also need CO2 emissions trading schemes, - a global carbon market, he argued.

"It is conceivable that we can get through the climate change crisis," Prof Malhi concluded. "Doing something about forests may be our most enduring legacy."

But what about local woodlands, vestiges of the great wildwood that once covered much of Britain? Wytham Woods, near Oxford, for instance. Prof Malhi is a Principal Investigator with Earthwatch on their climate change research project at Wytham Woods, and will be involved next year when a new field centre is launched there in March.

He said that Wytham is an important example of a fragment' of woodland, and that "these fragments are real reservoirs of biodiversity". One of the challenges is how they will persist once the effects of warming kick in, how less drought-tolerant species will cope and the hedges that serve as links between 'fragments'.

Next under discussion were wetlands, of which Oxfordshire has many since much of the county is on a floodplain plus some of the best examples of wetland habitat in the country.

Head of Wetland Conservation for the Wildfowl and Wetlands Trust, Slimbridge, Rob McInnes, who lives in Faringdon, began by reminding us how precious freshwater, "the lifeblood of the planet", is. Only 2.5 per cent of the water on earth is fresh water, most is locked up in polar snow and ice, and less than 1 per cent is an available resource for humans. This amounts to less than 0.01 per cent of total water on planet Earth.

Rob told us the degradation and loss of wetlands - lakes, rivers, ponds, marshes, swamps, peat bogs, wet woodlands, all dependent on freshwater - is even more rapid than for any other ecosystem. While freshwater habitats may cover only 0.8 per cent of the surface of the earth, their richness in species is greater than any other. Also the recharging of groundwater often comes from freshwater ecosystems.

He said wildlife and people depend on it. The economic value of undrained freshwater wetlands is often greater than drained. Economic security and fresh water wetland protection are inextricably linked, whether it is fresh water fisheries providing life-sustaining sources of animal protein such as the inland lakes in Malawi or seasonal floodplains in India, or grazing livestock on wet grassland in Oxfordshire.

We must try to get the message over, he said, to start appreciating our fragile wetlands - not just a free resource that is there to be drained and used, but for what they do for us and wildlife.

Dr Matt Frost, of the Marine Biological Association, put the case for oceans, and Prof Martin Price, from the Centre for Mountain Studies, Perth, for mountains.

But the polar regions won the audience over with the humorous, incisive presentation by Prof Lloyd Peck, of the British Antarctic Survey, though cuddly polar bear pictures possibly helped. He said: "If my other arguments don't work maybe this will."

It did. There was no sign of fatigue in the audience that night.

Earthwatch's website is www.earthwatch.org