A NATIONALLY important conservation area is being destroyed by teenage motorcyclists, who are also terrorising villagers near Durham City.

The rare limestone grassland at Sherburn Hill, a Site of Special Scientific Interest, is being churned up by the off-road bikers who are plaguing the area during the summer holidays.

Durham Police have promised to take action against the youths, mainly aged 14 to 18, following complaints from local people.

Patrols will be stepped up on land adjoining Cookshold Lane and South Street.

Geoff Barber, conservation officer for English Nature, said the bikers were ruining years of work put into maintaining the area.

There are only 270 hectares of limestone grassland left in Britain, and Sherburn Hill is regarded as an important example.

Mr Barber said: "We have had a large amount of motorcycles being ridden illegally on the site and the damage is quite extensive.

"There are large areas where they have been driving day after day, and there are now bare areas of land where the limestone grassland has been destroyed.

"It's also a hazard for walkers in the area and some villagers have been quite fearful of walking on the hill because these bikes can come out of nowhere. They also feel threatened because of the sort of people doing this, who are quite intimidating to the locals."

Inspector Steve Glass said police were worried about the safety of walkers, and the teenagers, who might not be in control of the powerful machines.

He said: "This is a problem which is clearly a real inconvenience to local people who wish to make legitimate use of the land. On private land, it is also illegal.

"Police motorcyclists will talk to those they find riding illegally, or without consideration for others and try to make them see the error of their ways.

"But they will also take any action they feel appropriate and any machine they have doubts about will be seized and its details of ownership checked."