The 'single biggest way' to reduce your environmental impact is to cut meat and dairy from your diet, according to researchers.
A large-scale study analysed almost 40,000 farms, across 119 countries and 40 different food products, to measure the environmental impact of farming.
It found meat and dairy production uses 83% of farmland and is responsible for 60% of agriculture's greenhouse gas emissions, while only providing 18% of calories and 37% of protein.
"A vegan diet is probably the single biggest way to reduce your impact on planet Earth, not just greenhouse gases, but global acidification, eutrophication, land use and water use," said lead researcher Joseph Poore, at the University of Oxford. "It is far bigger than cutting down on your flights or buying an electric car."
Researchers calculated that adopting a vegan diet can reduce carbon footprint by up to 73%. If the world stopped eating meat and dairy, global farmland use could be reduced by more than 75% - equating to an area the size of the EU, China, Australia and the US combined - and there would still be enough food to go round.
Some farms are far more sustainable than others, but, when compared to plant and vegetable production, even the most sustainably farmed beef was found responsible for six times more greenhouse gases and 36 times more land. "Avoiding consumption of animal products delivers far better environmental benefits than trying to purchase sustainable meat and dairy," Poore added.
The study did not present a vegan diet as the only solution to this problem, however. It stressed that producers of meat and dairy products should be monitoring their own environmental impacts and communicating their efforts and impacts to consumers. Other solutions suggested were taxes on meat and dairy foods, as well as clear labelling of their environmental impact. Subsidies of healthy, sustainable foods were also recommended.
Poore suggested that replacing the least sustainable half of meat and dairy production with plant-based alternatives would deliver two-thirds of the potential advantages by eradicating all meat and dairy farming. So, a reducetarian diet, an increasingly popular trend which reduce the amount of fish, eggs and dairy you consume, may be a really good way of making the smallest environmental impact possible.
Experts have also spoken out to praise the study and to stress that there is more than one solution to the issue it highlights. For instance, Dr Peter Alexander, a lecturer in Global Food Security at the University of Edinburgh, said, according to The Guardian: "There may be environmental benefits, e.g for biodiversity, from sustainably managed grazing. My personal opinion is we should interpret these results not as the need to become vegan overnight, but rather to moderate our [meat] consumption."
The study was published in the journal Science.