"Biodiversity is being destroyed irreversibly by human activities," said the appeal, made by leading biologists and environmentalists at the start of a conference in Paris on wildlife loss.

The proposal won the immediate endorsement of French President Jacques Chirac, who pledged to promote it at the UN Convention on Biological Diversity (CBD), an offshoot of the landmark 1992 Earth Summit in Rio de Janeiro.

The fate of humanity was intertwined with the fate of the environment, the scientists warned.

They said the millions of different species on Earth are the product of more than three billion years of evolution, "a natural heritage and a vital resource upon which humankind depends in so many different ways."

Almost everywhere, animals and plants are under threat from loss or degradation of habitat, from pollution of the soil, water and the air, from the exhaustion of soils, water tables and rivers by over-exploitation, "and, more recently, signs of long-term climate damage."

The signatories called for an intergovernmental panel, which would compile "reliable, scientifically validated" information for "public and private decision makers."

The appeal was launched at the first day of a conference gathering 1,200 experts and policymakers on species loss. The proposal is expected to be endorsed by the forum when it wraps up on Friday.

Sources said the panel's format would mirror that of a highly successful scientific committee on global warming set up in 1988.

That committee, the Intergovernmental Panel on Climate Change (IPCC), has had an enormous impact on the political agenda because its reports are detailed and take a neutral, science-based approach.

The task of the Paris conference is to focus on action on combating the planet's alarming loss of biodiversity, as wild species are battered by habitat loss and climate change.

The graphic opinion of some scientists is that the world is facing its biggest mass extinction in 65 million years, when the dinosaurs were wiped out by climate change inflicted by an asteroid impact.

Of the estimated 10-30 million species on Earth, only around 1.7 million have been identified and described. Each year, between 25,000 and 50,000 species die out, the vast majority of which have not even been identified, according to scientists' estimates.

The loss is likely to accelerate this century under the impact of habitat loss and rising global temperatures, stoked by fossil-fuel gases which trap the Sun's heat.

US scientist Edward Wilson, dubbed "the father of biodiversity" for his pioneering work in species conservation, declared that even though the signs all pointed to danger, Man could still save the planet.

He estimated it would cost about three billion dollars to draw up an inventory of the world's species, a project that would take 25 years.

Saving the 25 most-threatened "hotspots" that abound in species, such as the Amazonian forest, would cost 25 billion dollars, he said.

Many speeches at the opening day of the forum seized on Asia's tsunami disaster as a warning about environmental abuse.

Hamdallah Zedan, executive secretary of the UN's Convention on Biological Diversity, said the amplified toll from the December 26 calamity -- more than 227,000 dead -- was due in part to the destruction of natural buffers against killer waves.

"Once the immediate humanitarian needs are accommodated, it is time to rehabilite impacted ecosystems and to look at lessons learned," said Zedan.

"Early reports indicate that areas with healthier ecosystems, such as dense, intact mangrove forests and coral reefs, have been less affected than areas that have been disturbed or degraded," he said.

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