Organically farmed food has a larger climate impact than conventionally farmed food, due to the greater areas of land required. This is the finding of a new international study 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.

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 percent.

—Stefan Wirsenius, an associate professor from Chalmers

The reason why organic food is so much worse for the climate is that the yields per hectare are much lower, primarily because fertilizers are not used. To produce the same amount of organic food, you therefore need a much bigger area of land.

The ground-breaking aspect of the new study is the conclusion that this difference in land usage results in organic food causing a much larger climate impact.

The greater land-use in organic farming leads indirectly to higher carbon dioxide emissions, thanks to deforestation. 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.

—Stefan Wirsenius

Even organic meat and dairy products are—from a climate point of view—worse than their conventionally produced equivalents, claims Wirsenius.

Because organic meat and milk production uses organic feeds, 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.

—Stefan Wirsenius

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.

Resources

• Timothy D. Searchinger, Stefan Wirsenius, Tim Beringer & Patrice Dumas (2018) “Assessing the efficiency of changes in land use for mitigating climate change” Nature volume 564, pages 249–253 doi: 10.1038/s41586-018-0757-z