Urgent action is needed to minimise the impact of global warning on food production, climate change experts and landowners have warned.

Summer droughts are likely to become longer and more frequent, according to a study by the University of East Anglia's Climatic Research Unit and the Country Land and Business Association (CLA).

Senior climate scientist and report co-author David Viner said: "Hotter summers, increased droughts and sporadic, heavy rainfall have huge implications for agriculture.

Sea level rise remains a major threat."

Adapting to global warming will not be easy, warns the report.

It calls on politicians to help mitigate the effects by encouraging farmers to produce biofuels and plant trees for timber and to store carbon.

Study co-ordinator Michael Sayer, of the CLA, said the EU and government should devise a coherent strategy and infrastructure for processing biofuels.

"We should be encouraging landowners to produce biofuels and to enhance carbon stocks by planting more hardwood trees, which can be used as alternative construction material."

DEFRA secretary David Miliband agreed that land managers had a unique role in combating climate change because carbon could be stored in soil and trees.

But producers would also have to reduce agricultural emissions that cause global warming, he advised in a statement.

"Farming is a major source of methane and nitrous oxide - two powerful greenhouse gases which must be reduced," he said.

Agricultural levels of these pollutants have barely fallen over the past 15 years, according to DEFRA figures.

CLA president David Fursdon acknowledged that methane and nitrous oxide were by-products of farming.

But the government had yet to make guidance available to help farmers adjust their agricultural techniques and reduce emissions, he said.