Addressing the environmental crisis isn’t only about using renewable energy and driving less. If we truly want to address this crisis, we’ll have to change a lot of things in our lifestyles — including our diets. A third of all our greenhouse gas emissions come from food, and a disproportionate amount of those emissions come from meat.

This doesn’t mean we’ll all need to become vegetarian but at least bring down our meat consumption, especially in high-consumption countries. Now, a new study has put some numbers to it, looking at how beneficial certain diets could be to the environment. For instance, if the UK alone ate less meat, it would be like taking several millions of cars off the road.

Researchers at the University of Oxford have linked the dietary data of over 55,000 individuals in the UK to the environmental impact of the food they eat. They found that the dietary impact of vegans was about a third of the impact of those eating high-meat diets. They also found a 30% difference between high- and low-meat diets in terms of their environmental harm.

“Our dietary choices have a big impact on the planet. Cherry-picking data on high impact plant-based food or low impact meat can obscure the clear relationship between animal-based foods and the environment,” Peter Scarborough, study lead author from the Livestock, Environment and People (LEAP) project, said in a statement.

Food systems

Many studies have looked at the impact of the food we eat on the environment. Direct and greenhouse gas emissions of the global food system are estimated at around a third of the total emissions. The food system is also responsible for 70% of the world’s freshwater use, with three-quarters of the planet’s land area affected by human use.

We also know that plant-based diets are lower-impact than meat-based ones when it comes to environmental measures such as emissions, land use, and water use. However, studies about diets have generally made assumptions about people’s food intake, not taking into account how environmental impact varies depending on where food is produced.

To address this, Scarborough and the team looked at the way people actually eat, taking data from a sample of 55,000 people who completed a questionnaire on food frequency. They linked this to databases that estimate the environmental impacts of commonly used foods, also incorporating variation in where food is produced.

Changing diets

It’s the first study that looks at the impact of diets across five environmental measures (greenhouse gas emissions, land use, water use, water pollution and loss of species) across five groups – high-meat, low-meat, fish, vegetarian and vegan. In all cases,  the high-meat diet group showed a higher impact than any of the other groups, the researchers found.

A high-meat diet produces 10.24 kilograms of greenhouse gas emissions every day, while low-meat diets produce almost half – 5.37 kilograms per day, the study showed. For vegan diets, this is halved again to 2.47 kilograms a day. A high-meat diet also needs more water, about 890 liters of water a day, compared to 410 liters for a vegan diet.

In terms of land use, the high-meat diet requires 16.78 square meters of land per person. The figure lowers to 8.31 square meters for low meat-eaters and to 4.37 square meters for vegans. As for the loss of species, the high-meat diet contributes to the loss of 3.69 species per day, while low-meat diets are linked to 2.29 and vegans to 1.12, the researchers said.

“Our results, which use data from over 38,000 farms in over 100 countries, show that high meat diets have the biggest impact for many important environmental indicators, including climate change and biodiversity loss. Cutting down the amount of meat and dairy in your diet can make a big difference to your dietary footprint,” Scarborough said in a statement.

The study was published in the journal Nature.