A TEAM of university researchers has revealed that the northward march of many butterflies is being hindered by a serious loss of habitats in the region.

For a number of years, scientists have argued that climate change is pushing southern butterflies north because temperature rises of between one and one-and-a-half degrees Centigrade should lead to more food plants and better conditions for caterpillars.

While the theory still holds true, an investigation led by Professor Brian Huntley and colleagues at the University of Durham's Environmental Research Centre shows that the reality is very different.

The team, working with York and Leeds universities and the Butterfly Conservation charity, examined almost 500,000 records collected by 10,000 volunteers nationally, focusing on 46 butterflies at their northernmost limits in Britain.

It revealed that 75 per cent of species have declined over the 30-year period, despite warmer temperatures which should theoretically have seen them colonising more of the North-East.

Those which have become established in the region are among the nine most versatile such as speckled wood, which likes shady areas, and comma, which are now widespread.

However nine other supposedly adaptable butterflies and 90 per cent of 28 more specialised species have all declined significantly rather than expanded northwards.

Professor Huntley said: "What we are seeing is that it gets warm, which is good for butterflies, but because humankind has done so much damage, butterflies are not able to respond as they should."

The team has introduced one of the butterflies over which there is concern into a Durham County Council nature reserve at Wingate Quarry, east Durham.

Marbled white, a relative of speckled wood, has increased its British range by 66 per cent in recent years.

However, the team believes it should have done better, but has been restricted to dwindling grassland sites.

Last year, the team saw more than 150 butterflies emerge at the site and a new batch will start appearing in early July. The researchers hope that by monitoring how they fare they can help protect habitats elsewhere.

Professor Huntley said: "By studying the way organisms respond to change in their environment we can analyse the effects of the past and the present, and inform ourselves about likely conditions in the future.

"This should help us to understand the need to protect environments and safeguard habitats.

"If we do nothing, some species will disappear altogether from many areas. In the case of butterflies we looked at, the specialists will have little chance and the generalists will dominate."

His team is concerned that other creatures also experience problems from habitat destruction. Professor Huntley said: "If you look at creatures like ground beetles and snails, which are limited in the distance they can travel, and the next patch of habitat is further than they can walk or slither, they are not going to make it.