Organic farming produces more carbon emissions than traditional methods because it takes up a significantly greater amount of land, according to a study.

If England and Wales moved to a 100 per cent organic diet, food yields would be reduced by 40 per cent, scientists found. That would force more land overseas to be converted for farming to compensate, researchers said.

Organic farming – often touted as a more environmental alternative to traditional methods - does result in more carbon being stored in the soil but overall would result in an increase in emissions, according to the study published in Nature Communications.

Researchers said there were still benefits to organic farming but it needed to be combined with conventional methods.

Guy Kirk, a professor of soil systems at Cranfield University in Bedford, said: “Although there are undoubted local environmental benefits to organic farming practices, including soil carbon storage, reduced exposure to pesticides and improved biodiversity, we need to set these against the requirement for greater production elsewhere.”

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The study found said five times more land would need to be used for food production overseas if Britain’s diet became 100 per cent organic. Much of that land would be lower quality and therefore less productive, researchers said. Carbon-rich grassland would probably also be ploughed up as a result.

The findings suggest that without major changes in diet – such as a reduction in meat consumption – the world could not be fed exclusively through organic methods.

Dr Laurence Smith, lead researcher in the Cranfield University study, said: “Although resource use can be improved under organic management, there is a need to consider the potential effect on land-use.

“Under a 100 per cent organic scenario in England and Wales, a net-reduction in greenhouse gases would only be achievable if accompanied by a major increase in organic yields or widespread changes to national diets.”

The researchers said reducing waste and eating less meat had huge potential to reduce overall emissions. They added there was unlikely to be one single way to achieve environmentally sustainable food production and each country should be assessed on a case-by-case basis.

Professor David Reay, chair of carbon management at the University of Edinburgh, who was not involved in the research, said the findings were not surprising but added organic farming still had benefits for land use.

“We face a fiendishly difficult balancing act between cutting emissions, producing enough food, and protecting biodiversity and the myriad other gifts the land provides,” he said.

“Organic food production methods have an important role in achieving this balance – you can use all the precision farming methods and fancy fertilisers you like, but if the pollinators are all killed by pesticides you’re still in a heap of trouble.

“Food production in some areas must become much more efficient so as to free up land elsewhere for carbon sequestration.