Thousands of species could be lost if action is not taken to halt global warming, a conservation charity warns.
Emissions must be cut to save wildlife, the RSPB says.
John Lanchbery, of the Royal Society for the Protection of Birds, says wildlife is already being affected.
It will take very little further climate change to "catastrophically" affect other species, he will tell an Exeter scientific conference.
Action must be taken to cut the greenhouse gases which cause air and sea temperatures to rise, he says.
Mr Lanchbery is to address delegates at the three-day Avoiding Dangerous Climate Change conference, which opens on Tuesday.
He will tell them: "It is not a question of whether but how, we tackle climate change if we care at all about our health, our food and water supplies and our wildlife."
RSPB research scientists have previously warned that 25% of land-based species have no future if temperatures rise as climate experts predict.
Despite this warning, greenhouse gas levels are still rising, Mr Lanchbery says.
The RSPB says global temperature rise must be limited to less than 2C above that in pre-industrial times.
That means global emissions must start to fall in the next decade.
Although developed countries, particularly the US, must take the lead in cutting emissions, the large, rapidly industrialising countries should limit their emissions too, it says.
Developed countries need to cut their emissions by at least 60% by 2050 but even that reduction may be too small to save many species.
The charity says 2004 was the worst for breeding seabirds on UK shores, probably due to the movement of plankton from warming coastal waters.
It says climate change has also probably caused the extinction of the golden toad of Costa Rica and threatens to do the same to the Scottish crossbill bird.
"If we lose it now, we will never get back the wealth of wildlife this planet boasts," Mr Lanchbery says.
Friends of the Earth is also calling for more action to cut greenhouse gases as the conference opens.
It says carbon dioxide levels in the UK have not fallen since Labour came to power in 1997 and is calling on Prime Minister Tony Blair to act.
The government has pledged to cut carbon dioxide levels to 20% below 1990 levels by 2010.
Last week Mr Blair called for international action to tackle climate change in a speech at the World Economic Forum in Davos, Switzerland.