London: Organic food has a bigger climate impact than conventionally farmed food, due to the greater areas of land required, according to a study.
Researchers from the Chalmers University of Technology in Sweden developed a new method for assessing the climate impact from land-use, and used this, along with other methods, to compare organic and conventional food production.
The results, published in the journal Nature, show that organic food can result in much greater emissions.
"Our study shows that organic peas, farmed in Sweden, have around a 50 per cent bigger climate impact than conventionally farmed peas," said Stefan Wirsenius, an associate professor at Chalmers.
"For some foodstuffs, there is an even bigger difference -- for example, with organic Swedish winter wheat the difference is closer to 70 per cent," Wirsenius said.
The reason why organic food is so much worse for the climate is that the yields per hectare are much lower, primarily because fertilisers are not used.
To produce the same amount of organic food, you therefore need a much bigger area of land, researchers said.
"The greater land-use in organic farming leads indirectly to higher carbon dioxide emissions, thanks to deforestation," said Wirsenius.
"If we use more land for the same amount of food, we contribute indirectly to bigger deforestation elsewhere in the world," he said.
Even organic meat and dairy products are -- from a climate point of view -- worse than their conventionally produced equivalents, researchers said.
Since organic meat and milk production uses organic feed-stock, it also requires more land than conventional production, they said.
"This means that the findings on organic wheat and peas in principle also apply to meat and milk products," Wirsenius said.
"We have not done any specific calculations on meat and milk, however, and have no concrete examples of this in the article," he said.
The researchers used a new metric, which they call "Carbon Opportunity Cost", to evaluate the effect of greater land-use contributing to higher carbon dioxide emissions from deforestation.
This metric takes into account the amount of carbon that is stored in forests, and thus released as carbon dioxide as an effect of deforestation.
The study is among the first in the world to make use of this metric.
"The fact that more land use leads to greater climate impact has not often been taken into account in earlier comparisons between organic and conventional food," said Wirsenius.