Organic farming increases biodiversity but not enough to compensate for the lower yields, according to an analysis of English farms.

Researchers from the University of Leeds' Faculty of Biological Science found biodiveristy to be an average of 12 per cent higher on organic compared to conventional farms.

However, yields of the crop they compared, winter wheat, were on average 55 per cent lower.

Rather than dismissing organic farming all-together, researchers said their findings showed that in order to keep up with worldwide demand for increased food production, conservation management should be separated from food production.

Co-author Professor Tim Benton said while the UK and EU did need targets for both biodiversity and food production, there was a debate to be had about the best way of achieving the targets at a regional and farm level.

'If you want to produce yields in food and biodiversity then rather than trying to do both our results show that specialising in one area may be the better approach,' he said.

Professor Benton said organic farming may be best kept away from highly productive areas of the UK like East Anglia. In contrast, areas like the Yorkshire Dales or West Country, which cannot deliver the same yields, would be more suited to conversion to organic.

'To meet future demands of food production, we will need to keep farming our most productive areas in the most intensive way we can – and potentially offset that by managing some of our remaining land exclusively as wildlife reserves,' he explained.

The Conservation Trust said separating food production and conservation would lead to a 'two-tier countryside; part industrial and part play ground'.

'Our countryside is farmed from coast to coast and the wildlife it contains reflects the historic patterns of agriculture from chalky downlands to clay vales. We need all farms to retain their wildlife,' said director of policy Dr Stephen Tapper.

The Soil Association criticised the study for basing claims about yield losses on one single crop, winter wheat. A study by Reading University in 2009 found that switching to organic would lead on average to only 30 per cent drops in wheat yields and actually lead to increases in beef and lamb production.

The Soil Association also criticised the study for underestimating the benefits of organic farming by comparing individual fields rather than the entire farms.

However, Professor Benton said organic farms had come out well in earlier research into biodiversity and wildlife because they tended to be found in areas with smaller fields, more hedges and woodland so they started with an advantage.

The Soil Association said this ignored the fact that organic farms did usually have more and smaller fields. Professor Benton said his study wanted to see if organic farming was still as good for wildlife if these landscape effects were taken out of the equation.

Useful links
Leeds University study
Reading University study