Intensive farming and climate change have together had a devastating impact on British animals and plants since the 1970s, research has shown.

A combination of the two factors is said to be the main driving force behind changes that have seen farmland lose half its birds and a third of its butterflies.

Significant declines of beetles, bees, grasshoppers, amphibians, reptiles and mammals have also occurred, according to The State of Nature report, a major stock-take of UK wildlife published in 2013.

Plants have also been affected, with 14 mosses and liverworts already driven to extinction.

The new research, which looked at 400 species across the UK, identified intensive management of agricultural land and climate change as the factors that have chiefly affected wildlife since 1970.

Of the two, changing farming methods had been the most negative.

Dr Mark Eaton, from the Royal Society for the Protection of Birds, who co-led the study published in the journal Public Library of Science ONE, said: "Farmland covers so much of our country, up to three quarters of the UK.

"Changes to farming practices in 1970s and 80s have squeezed wildlife out of the countryside - things like increasing use of fertilisers and pesticides, and the loss of hedgerows.

"In recent years that trend has slowed and the situation now looks more positive, though there's still a long way to go. Farmers have the ability to start encouraging wildlife with support from policymakers."

Measures farmers could take without harming their livelihoods included providing more hedgerows, avoiding pesticides in certain areas, and allowing wild flowers to flourish at field margins.

"There are two arguments for taking care of the countryside," said Dr Eaton. "One is that nature has a right to exist; the other is that it's good for us. There's a growing body of evidence that listening to bird song or seeing butterflies benefits our mental health.

"Preserving the countryside also encourages people to be more active, and helps the tourist industry."