If you joined Americans in tucking into a Thanksgiving dinner last week, no doubt the centrepiece on the table was roast turkey.

“Meat is really intimately tied with a lot of traditions and festivities,” says Emma Garnett, a postdoctoral researcher who studies behaviour change and sustainable diets at the University of Oxford in England. Even outside holiday meals, she says, meat eating has become excessive.

In industrialised countries such as the United States, people often consume far more meat than dietary guidelines recommend. Scientific data now shows this is not only bad for people’s health – but also the planet.

“Food systems are responsible for a third of global greenhouse gas emissions, which is huge,” says Stacy Blondin, a behavioural science associate at the non-profit World Resources Institute (WRI) based in Washington. It is the production, transport and consumption of animal-based foods specifically that are the dominant source of food-related emissions.

Some of the highest-emission foods come from cows and other animals which roam across hectares of land emitting methane, a greenhouse gas, during their unique digestion process.