One in five plants 'faces extinction'

The analysis indicates an estimated 380,000 plant species are as much at risk of disappearing as the planet's mammals and are more under threat than birds.

Plants are most at risk from the destruction of their habitat by humans, according to the assessment by scientists at Kew Gardens and the Natural History Museum in London and the International Union for Conservation of Nature.

Vegetation is under pressure from human activities across the world - from the destruction of the Atlantic rainforest in South America to slash-and-burn land clearance in Madagascar, palm oil plantations in Indonesia and intensive agriculture in Europe and the US, the experts say.

The study, the Sampled Red List Index for Plants, indicates that 80,000 to 100,000 plants could be at risk of extinction globally - more than 50 times the number of species known to be native to the British Isles.

The study looked at a representative sample of 7,000 plants from five major groups of plants. It found that 22 per cent of the 4,000 species which were carefully assessed were classified as critically endangered, endangered or vulnerable to extinction.

A further 10 per cent of plants, including the humble snowdrop - a non-native species that has become widely established in the UK but is losing ground in its natural habitat in central and eastern Europe - are not yet threatened but will be without conservation action.

The majority of threatened plant species were found in tropical rainforest, which is home to a wide variety of species but is under great pressure from humans, while islands in the middle of the ocean, such as Christmas Island and Bermuda, also had a high proportion of threatened species.

Professor Stephen Hopper, director of the Royal Botanic Gardens, Kew, said: "This study confirms what we already suspected, that plants are under threat and the main cause is human-induced habitat loss.

"Plants are the foundation of biodiversity and their significance in uncertain climatic, economic and political times has been overlooked for far too long.

"We cannot sit back and watch plant species disappear - plants are the basis of all life on Earth, providing clean air, water, food and fuel. All animal and bird life depends on them and so do we."

The global analysis of the state of plants comes weeks before governments from around the world meet in Nagoya, Japan, to discuss the planet's wildlife and habitats and set new targets on protecting biodiversity over the next decade.

Global targets to significantly reduce the loss of wildlife by this year have been missed. The targets to significantly reduce the loss of biodiversity by 2010 were agreed in 2002, but scientists warned earlier this year that the rate at which species and habitats were disappearing had not slowed.

It is hoped the new assessment will give politicians information on an area of wildlife that has not been as extensively assessed as mammals, amphibians, birds and other creatures, as they meet to agree new targets.

Eimear Nic Lughadha, from Kew, said: "What we want to do is remind politicians it's not just about the big furry animals and charismatic birds."

She said biodiversity was underpinned by the "perhaps less attractive organisms" including insects and plants, which made up the foundations of the natural world. And as new species of plant were still being discovered - which were likely, if they had not already been found, to be rare and therefore at higher risk of extinction - the assessment that a fifth of plants were at risk was likely to be conservative.

"We think it is a conservative estimate of the overall rate of threat to plants, and we suspect if we had a full inventory, the percentage would be at least this high and probably a little bit higher," she said.

The assessment, based on criteria including the range, populations and numbers of individual plants, is the first of its kind and so cannot show the rate of decline.

But as it does reveal which groups of plants are most at risk, and where and why species are threatened, it is hoped it will help conservation action to protect biodiversity.