Organically farmed food has a bigger climate impact than conventionally farmed food, due to the greater areas of land required and a resultant increase in deforestation globally. 

That’s the conclusion of a new international study involving Chalmers University of Technology, Sweden, published in the journal Nature.
The researchers 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 show that organic food can result in much greater emissions.
Previous studies – conducted by the USDA, Rodale Institute, Northeastern University and others – have shown that organic farming performs better that conventional in this area by locking away more carbon in the soil. 
“Our study shows that organic peas, farmed in Sweden, have around a 50 percent bigger climate impact than conventionally farmed peas. For some foodstuffs, there is an even bigger difference – for example, with organic Swedish winter wheat the difference is closer to 70%,” says Stefan Wirsenius, an associate professor from Chalmers, and one of those responsible for the study.
The Swedish researchers say the reason why organic food is “so much worse for the climate” is down to lower yield rates for organic crops, leading to higher land use.
“The greater land-use in organic farming leads indirectly to higher carbon dioxide emissions, thanks to deforestation,” explains Stefan Wirsenius. “The world’s food production is governed by international trade, so how we farm in Sweden influences deforestation in the tropics. If we use more land for the same amount of food, we contribute indirectly to bigger deforestation elsewhere in the world.”
Even organic meat and dairy products are – from a climate point of view – worse than their conventionally produced equivalents, claims Stefan Wirsenius.
“Because organic meat and milk production uses organic feed-stocks, it also requires more land than conventional production. This means that the findings on organic wheat and peas in principle also apply to meat and milk products. We have not done any specific calculations on meat and milk, however, and have no concrete examples of this in the article,” he explains.
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 their deforestation hypothesis. This metric takes into account the amount of carbon that is stored in forests, and then released as carbon dioxide as an effect of deforestation.
“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,” says Stefan Wirsenius. “This is a big oversight, because, as our study shows, this effect can be many times bigger than the greenhouse gas effects, which are normally included. It is also serious because today in Sweden, we have politicians whose goals is to increase production of organic food. If those at goals is are implemented, the climate influence from Swedish food production will probably increase a lot.”
Long-term trials conducted by the US Department of Agriculture, looking at a wider set of environmental impacts, produced generally positive findings for organic, summarised as:
The organic systems:
●Have more-fertile soil
●Use less fertilizer and much less herbicide
●Use less energy
●Lock away more carbon in the soil
●Are more profitable for farmers
Conventional systems:
●Have higher yields
●Are best at reducing erosion (when a no-till system is used)