Life on earth is facing a major crisis with thousands of species threatened with imminent extinction - a global emergency demanding urgent action. This is the view of 19 of the world’s most eminent biodiversity specialists, who have called on governments to establish a political framework to save the planet.

The planet is losing species faster than at any time since 65 million years ago, when the earth was hit by an enormous asteroid that wiped out thousands of animals and plants, including the dinosaurs. Scientists estimate that the current rate at which species are becoming extinct is between 100 and 1,000 times greater than the normal “background” extinction rate - and say this is all due to human activity.

The call for action comes from some of the most distinguished scientists in the field, such as Georgina Mace of the UK Institute of Zoology; Peter Raven, the head of the Missouri Botanical Garden in St Louis, and Robert Watson, chief scientist at the World Bank. “For the sake of the planet, the biodiversity science community had to create a way to get organised, to co-ordinate its work across disciplines and together, with one clear voice, advise governments on steps to halt the potentially catastrophic loss of species already occurring,” Dr Watson said.

In a joint declaration, published today in Nature, the scientists say that the earth is on the verge of a biodiversity catastrophe and that only a global political initiative stands a chance of stemming the loss. They say: “There is growing recognition that the diversity of life on earth, including the variety of genes, species and ecosystems, is an irreplaceable natural heritage crucial to human well-being and sustainable development. There is also clear scientific evidence that we are on the verge of a major biodiversity crisis. Virtually all aspects of biodiversity are in steep decline and a large number of populations and species are likely to become extinct this century.

“Despite this evidence, biodiversity is still consistently undervalued and given inadequate weight in both private and public decisions. There is an urgent need to bridge the gap between science and policy by creating an international body of biodiversity experts,” they say.

More than a decade ago, Edward O Wilson, the Harvard naturalist, first estimated that about 30,000 species were going extinct each year - an extinction rate of about three an hour. Further research has confirmed that just about every group of animals and plants - from mosses and ferns to palm trees, frogs, and monkeys - is experiencing an unprecedented loss of diversity.

Scientists estimate that 12 per cent of all birds, 23 per cent of mammals, a quarter of conifers, a third of amphibians and more than half of all palm trees are threatened with imminent extinction. Climate change alone could lead to the further extinction of between 15 and 37 per cent of all species by the end of the century, the scientists say: “Because biodiversity loss is essentially irreversible, it poses serious threats to sustainable development and the quality of life of future generations.”

There have been five previous mass extinctions in the 3.5 billion-year history of life on earth. All are believed to have been caused by major geophysical events that halted photosynthesis, such as an asteroid collision or the mass eruption of supervolcanoes. The present “sixth wave” of extinction began with the migration of modern humans out of Africa about 100,000 years ago. It accelerated with the invention of agriculture 10,000 years ago and began to worsen with the development of industry in the 18th century.

Anne Larigauderie, executive director of Diversitas, a Paris-based conservation group, said that the situation was now so grave that an international body with direct links with global leaders was essential. “The point is to establish an international mechanism that will provide regular and independent scientific advice on biodiversity,” Dr Larigauderie said. “We know that extinction is a natural phenomenon but the rate of extinction is now between 100 and 1,000 times higher than the background rate. It is an unprecedented loss.”

The scientists believe that a body similar to the Intergovernmental Panel on Climate Change could help governments to tackle the continuing loss of species. “Biodiversity is much more than counting species. It’s crucial to the functioning of the planet and the loss of species is extremely serious,” Dr Larigauderie said. “Everywhere we look, we are losing the fabric of life. It’s a major crisis.”

Species under threat

Land mammals

The first comprehensive inventory of land mammals in 1996 found a quarter, including the Iberian lynx were in danger of extinction. The situation has worsened since.

Reptiles & amphibians

The Chinese alligator is the most endangered crocodilian - a survey in 1999 found just 150. Frogs, toads, newts and salamanders are the most threatened land vertebrates.

Birds

One in five species are believed to be in danger of extinction; that amounts to about 2,000 of the 9,775 named species. Most are at risk from logging, intensive agriculture, trapping and habitat encroachment. Many experts believe the Philippine eagle and wandering albatross could become extinct this century.

Marine life

The oceans were thought to be immune from the activities of man on land, but this is no longer true. Pollution, overfishing, loss of marine habitats and global warming have a dramatic impact on biological diversity. More than 100 species of fish, including the basking shark are on the red list of threatened species.

Plants

Many plants have yet to be formally described, classified and named - and some are being lost before they have been discovered by scientists. Plants of every type are being lost.

Insects & invertebrates

Many insects are wiped out by pesticide-reliant intensive agriculture. Others, such as the partula tree snails of Tahiti are menaced by invasive species.

By Steve Connor, Science Editor