Aquaculture can emit more methane, and create more greenhouse gases, than cows, whilst one pint of beer can create three times more emissions and use four times more land than another. The findings are in a new study published in the journal Science.
Researchers at Oxford University and the Swiss agricultural research institute, Agroscope, created the most comprehensive database yet on the environmental impacts of nearly 40,000 farms and 1,600 processors, packaging types and retailers. This allowed them to assess how different production practices and geographies lead to different environmental impacts for 40 major foods.
They found considerable differences in environmental impact between producers of the same product.
For example, high-impact beef producers create 105kg of CO2 equivalents, which is 12 times greater than low-impact producers. High-impact farms also use 370m2 of land per 100 grams of protein, or 50 times more than those with low impacts.
Plants, generally, had a much smaller footprint. Low-impact beans, peas and other plant-based proteins can create just 0.3kg of CO2 equivalents (including all processing, packaging, and transport), and use just 1m2 of land per 100 grams of protein.
This variation in impacts is observed across all five indicators the scientists assessed – greenhouse gas emissions, land use, water use, eutrophication and acidification.
“Two things that look the same in the shops can have extremely different impacts on the planet,” said Joseph Poore, from the Department of Zoology and the School of Geography and Environment at Oxford University.
Poore said new technology to monitor agriculture is needed, as well as environmental labels that allowed consumers to compare low and high impact products. Policy also needs to be fine-tuned – an approach to reduce environmental impacts or enhance productivity that is effective for one producer can be ineffective or create trade-offs for another, the experts noted.
“We need to find ways to slightly change the conditions so it’s better for producers and consumers to act in favour of the environment,” he said. “Environmental labels and financial incentives would support more sustainable consumption.”
The researchers also discovered that producers have limits on how far they can reduce their impacts. They found that the variability in the food system failed to translate into animal products with lower impacts than vegetable equivalents. For example, a low-impact litre of cow’s milk uses almost two times as much land and creates almost double the emissions of an average litre of soymilk.
Livestock-free diets, therefore, deliver greater environmental benefits than purchasing sustainable meat or dairy, they concluded. Plant-based diets reduce food’s emissions by up to 73% depending on the region, and would require 76% less farmland.
