When you think of major sources of greenhouse gas emissions, agriculture might not immediately come to mind. However, food production contributes about a quarter of all emissions, a magnitude comparable with other major sectors like energy production and transportation. Food production is also responsible for about 70% of fresh water use and takes up more than one-third of all potentially cultivatable land.
Thus, changes in diet can potentially have big effects on the environment. But scientists are just beginning to quantify these impacts and identify the dietary changes necessary to achieve them.
“I think if we want to reduce our environmental footprint, we definitely need to pay attention to our diets,” says Lukasz Aleksandrowicz, a PhD candidate at the London School of Hygiene and Tropical Medicine.
Aleksandrowicz and his colleagues systematically reviewed scientific studies measuring the environmental impacts of shifting from a typical Western diet to a variety of proposed sustainable diets. These included vegetarian diets, vegan diets, and Mediterranean diets, as well as more fine-tuned changes, such as replacing beef with chicken or reducing the total number of calories consumed.
The review showed that sustainable diets could reduce greenhouse gas emissions and land use by as much as 70% and reduce water use by 50%. Most of the scenarios achieved smaller environmental footprints by replacing animal-based foods, especially beef, with plant-based foods.
Although consuming less meat had a positive environmental impact in most of the studies reviewed, there may be some trade-offs. For instance, diets that might be favorable in terms of reducing greenhouse gas emissions might have more detrimental effects on other environmental indicators like water use. Aleksandrowicz says that more research needs to be done to identify the environmental impacts of specific food items.
Another complication is that most of the available studies focus exclusively on Europe and the U.S. The results may not make sense for low-income countries or in populations that rely economically on herding cattle or other livestock.
Aleksandrowicz says that although more work is needed to evaluate the impacts of shifting to sustainable diets, the major action we can take to reduce environmental impacts from agriculture is decreasing our meat consumption.
“It’s important to put the environmental impacts of agriculture on people’s radar,” he says. “I hope this kind of research helps people understand that the food choices they make have an impact on the environment, and that they can make more sustainable choices.”
Aleksandrowicz, L., Green, R., Joy, E. J. M., Smith, P., and Haines, A. (2016). The Impacts of Dietary Change on Greenhouse Gas Emissions, Land Use, Water Use, and Health: A Systematic Review. PLOS One 11(11): e0165797. doi: 10.1371/journal.pone.0165797.