The number of butterflies found on farms has plummeted by 30 per cent in the last decade, according to a Government-backed study.

Biodiversity Minister Jim Knight said research carried out by Butterfly Conservation for the Department for Environment, Food and Rural Affairs, highlighted the acute problems faced by butterflies in the English landscape, but also demonstrated the potential for Environmental Stew-ardship to help find solutions.

He said: "Butterflies are an iconic species in their own right, and they can be good indicators of the health of the entire ecosystem, so this decline is worrying," he said.

"The implications for other insects, birds and mammals are concerning. The fact that this overall decline has taken place across the board means that we need to look very carefully at how we can help butterflies throughout the countryside and on SSSIs.

"We also need to monitor how well Environmental Stewardship supports butterfly populations."

The study calculated trends for 40 butterfly species across 820 sites, of which 371 were in agri-environment schemes. Since the monitoring was carried out, new agrienvironment schemes, Environmental Stewardship, have been launched in England.

The study also identified that butterflies declined at specific sites for a variety of reasons, including a lack of understanding of habitat requirements by land managers, overgrazing by rabbits, inappropriate bracken or scrub cutting regimes, and over or under-grazing.

Mr Knight said there were some encouraging signs that agri-environment schemes were starting to have an effect on butterfly population decline. He said: "On sites covered by agri-environment schemes, we are seeing improved trends for six of the eight species listed as priori-ties under the Biodiversity Action Plan (BAP)."

Dr Tom Brereton, who spearheaded the research for Butterfly Conservation, said: "The results of the survey are worrying but we are optimistic about the new scheme."