Do you know the carbon footprint of your food choices?

Between 19% and 29% of global greenhouse gas emissions come from food production, with beef and lamb the biggest contributors, so shifting diets towards greater fruit and vegetable intake is a promising strategy for reducing climate change.

Lead author Dr Adrian Camilleri wanted to know how well consumers understood the carbon consequences of their food choices, as previous research had shown people significantly underestimate the carbon emissions from electrical appliances.

"With an appliance such as a heater you can feel the energy used and see an electricity bill at the end of the month, so the impact is quite salient, whereas the impact of food production is largely invisible," says Dr Camilleri.

The study, published in the journal Nature Climate Change, asked more than 1000 people to estimate the energy embedded in 19 foods and 18 appliances, and the amount of greenhouse gas emissions associated with those appliances and foods.

The researchers found participants significantly underestimated energy consumption and greenhouse gas emissions for both electrical appliances and foods -- but food was more severely underestimated.

"If you ask people to guess the difference between items such as beef and vegetable soup on the environment they assume there is not much difference, but beef soup creates more than 10 times the amount of greenhouse gases than vegetable soup," says Dr Camilleri.

"This is a bit of a blind spot because if someone wants to reduce their greenhouse gas emissions, they might think to turn off the heater, drive less or fly less. Very few people think to eat less beef."

The researchers also looked at whether they could improve people's perception of the environmental impact of their food choices through the use of labelling, in the same way that a five-star rating system for electrical appliances conveys energy use.

They presented 120 participants with a choice of soups to buy. When the soups had a carbon footprint label, participants bought fewer beef soups and more vegetable soups than when there was no label provided.

The research suggests that the introduction of carbon footprint labels on food items could be a simple intervention to increase understanding of energy use and greenhouse gas emissions from food production, and so reduce environmental impacts.

Greenhouse gases emerging from beef and lamb production include those created in the production of fertiliser for feed, methane emitted from the animals, livestock transportation and the loss of trees to clear land for pasture.

A vegan diet based on fruits, vegetables and grains has the least impact on the environment, with pork, chicken and fish creating a moderate impact, and beef and lamb the greatest impact.

"The choices we make at the dinner table can have a significant impact on global challenges such as climate change, and our research shows consumers are keen to make that choice," says Dr Camilleri.