Research casts doubt over organic virtues

The university said its report is based on "the most detailed like-for-like comparisons of organic and conventional farming to date". Read the report in full (PDF, 436kb)

"Our results show that to produce the same amount of food in the UK using organic rather than conventional means, we'd need to use twice the amount of land for agriculture," said Tim Benton, the professor who led the research. "As the biodiversity benefits are small, the lower yield may be a luxury we can't afford."

But the Soil Association, leader of the organic lobby, said the university and Prof Benton were over-interpreting a study which only covered yields from cereals – wheat, barley and oats – and previous studies had found organic vegetables did much better.

Prof Benton said nothing could make up for productivity in winter-planted wheat at less than 50 percent of the average, and added "The UK lives on cereals."

The Leeds Faculty of Biological Science carried out its research in the north Midlands and south west of England, where it was easiest to find comparisons between organic and conventional farming in matching soil, landscape, environmental and climatic conditions.

Previous research had failed to take account of all of the 30 influential factors the Leeds team considered, according to Prof Benton.

His team's report, published yesterday in the online journal Ecology Letters, was funded under the Rural Economy Land Use programme which enables research into the social, economic, environmental and technological challenges faced by rural areas and is part-funded by the Scottish government and Department for Environment, Food and Rural Affairs.

Prof Benton told the Yorkshire Post: "Over the next 40 years, we're going to have to double food production worldwide to keep pace with population increases and the Government wanted scientists to work together to find the best way forward, instead of ecologists shouting loudly at agriculturalists.

"I am a conservation biologist and I started with the idea that organic farming was definitely good. I was surprised by what we found."

As well as finding organic yields less than half those of chemically-assisted farming, his team found improved biodiversity averaging just 12 per cent – using a formula which took into account both the numbers and the variety of species found, in everything from worms to mammals, on both arable fields and pasture. The figure was improved to about 18 per cent where there were large areas of organic conditions but not by nearly enough to make up for the extra land needed, said the Leeds team.

One striking finding was that organic land had fewer small birds – the usual quick measure of environmental health. Research is continuing but first impressions were that organic farms attracted more avian

predators, like crows.

Another unforeseen negative was that neighbouring farms tended to use more herbicides to counteract weed seeds coming across.

Prof Benton added: "The wildlife would be better off if we kept food production and conservation as separate activities.

"Organic methods may be a useful part of the land management mix for the less productive parts of the UK, particularly if policies can encourage farmers to coordinate activities to maximise the benefit to wildlife across a larger area.

"However, given the lower yield and the limited biodiversity benefit of organic farming, it isn't sustainable to promote it as the best or only method of agriculture."

Evangelists point out the problems

Organic methods are followed on less than five percent of British farmland but their evangelists, led by the Soil Association, want to see much more.

The Leeds report is, however, the latest in a series to challenge the conventional wisdom that not using fertilisers and pesticides is better for the environment and for the food.

Lord Melchett, Norfolk farmer and chief spokesman of the Soil Association, said: "Productivity should be judged according to total resources used per unit of output, including the oil consumed to produce artificial fertilisers, rather than simply yield per hectare."

Other organic champions pointed out the Leeds study compared fields rather than farms – and organic farms generally have more and smaller fields. And the yield conclusions were based almost entirely on wheat, which is notoriously difficult to grow without weedkillers.