A team of British researchers is calling for reform of Europe's agricultural policy to allow birds and other wild creatures a greater chance of survival.

The team estimates that, in Britain alone, loss of biodiversity has meant the disappearance of 10 million breeding individuals of 10 farmland bird species in the past two decades.

They say: "Parallel changes have taken place in many other European countries".

History repeats itself

"In all, 116 species of farmland birds - one-fifth of European avifauna - are now of conservation concern."

The researchers, all ornithologists, are from the Royal Society for the Protection of Birds, the British Trust for Ornithology, and the Department of Zoology at the University of Oxford.

Skylarks are dwindling fast

The group, whose work is reported in the science journal Nature, says what is happening amounts to "a second silent spring".

But this time it is not poisoning by pesticide residues that is to blame.

Intensification of agriculture "is about making as great a proportion of primary production as possible available for human consumption. To the extent that this is achieved, the rest of nature is bound to suffer".

They identify some key changes in British farming over the last 30 years:

• land drainage
• hedgerow removal
• introduction of new crop types
• increased use of agrochemicals, and a move towards monoculture
• a change from spring to autumn sowing
• the harvesting of grass for silage
• a reduction in the traditional rotation of crops.

The researchers say most of the evidence that farming is to blame for what is happening to the birds "is by association, but in sum total it is damning".

"Annual BTO censuses of 42 species of breeding birds show that 13 species living exclusively in farmland, such as the skylark and corn bunting, declined by an average of 30% between 1968 and 1995.

"Yet 29 species of habitat generalists, such as the carrion crow and the wren, have increased by an average of 23%."

The cirl bunting: One of the success stories

And the declines of four species - grey partridge, cirl bunting, corncrake and stone curlew - have been reversed, at least locally, by changes in farming practices.

The researchers say there are agricultural schemes in the UK that could help biodiversity.

But there is "no magic bullet with which to reverse the declines of a large suite of species . . . the most general prescription is to reverse the intensification of agriculture".

Areas for research they recommend include the effects of introducing more variety into farming.

Genetically-modified crops

They also want an investigation of the trade-offs between conservation benefits and the profitability of farming, and of "the trade-offs (or synergies) between conservation of different taxonomic groups".

And they say genetically-modified (GM) crops may have a part to play.They want thorough and continuing evaluation of GM plants to make sure there is no risk.