FARMERS and landowners are urged to help control rabbits which are wreaking havoc on some of the most important wildlife sites in the Yorkshire dales.

English Nature warned that damage by vast numbers of rabbits affected 75pc of the area's best ash woods, many designated sites of special scientific interest, grassland and limestone pavement.

Grassland was reduced to tightly-cropped lawn as burrowing and scraping by the animals encouraged nettles, thistles and the potentially fatal ragwort.

English Nature, the government's wildlife agency, says a more co-ordinated approach to rabbit control is needed, backed by government and European funding, if wildlife sites are to be conserved.

The organisation is supporting work this winter at two sites in the dales: Haw Bank wood, near Carperby, in Wensleydale, and Bastow wood in Wharfedale.

Experts will use a combination of special fencing, shooting and gassing to reduce the rabbit population and restore woodland and plant life.

In recent years, the organisation has fenced tens of hectares of woodland and invested in hundreds of humane rabbit traps, but the battle is still being lost.

Dr Paul Evans, a conservation officer at English Nature's Leyburn offices, said: "Despite the best efforts of farmers and land managers, rabbit populations are at epidemic levels in parts of the dales and wildlife is suffering. Even though we have fenced off many important woodlands, rabbits are still preventing new growth and damaging older trees.

"With one rabbit doe capable of producing over 20 young in a year, and their offspring also breeding in the same season, added to the fact that eight rabbits graze the same amount of grass as a single sheep, the scale of the problem is clear."

Winter was the best time to control rabbits, before the breeding season, and farmers and landowners were encouraged to work with the organisation to help prevent re-infestation next spring.

Mr Colin Newland, of English Nature at Leyburn, said rabbit populations had boomed since the myxomatosis epidemic of the 1950s. "People also don't tend to eat rabbit as much these days so there is perhaps less incentive to control the population," he added.

English Nature hoped for extra cash from the British government and the European union to fund more long-term solutions to the problem.