The eating habits of 55,000 people were analysed by researchers from the University of Oxford who found meat-free eating to have a much lower environmental impact on land use, water pollution risk, water use and biodiversity loss.
Professor Peter Scarborough, the lead author of the study, concluded that “cutting down the amount of meat and dairy in your diet can make a big difference to your dietary footprint”.
Agriculture is a major source of deforestation and biodiversity loss while around three-quarters of ice-free land has been adopted by humans, according to the UN.
The food system is responsible for 70% of the world’s freshwater use and 78% of freshwater pollution and is the second-largest producer of greenhouse gases after energy.
In 2015, the direct and indirect greenhouse gas emissions were around a third of the total emissions for that year, a previous study has found.
Other research has shown that plant-based diets produce fewer greenhouse gases, use less water and are healthier for the body but may not have taken into account how and where that food is produced, the Oxford University team said.
The study, which was published in Nature Food, asked 55,000 people in the UK to fill out a questionnaire and categorised them into vegans, vegetarians, pescatarians and high and low-meat eaters.
The team then connected the information with databases estimating the environmental impact of various food to include in the final analysis.
Prof Scarborough said: “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.
“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.”
Compared to high-meat diets, vegans were found to have a quarter of the environmental impact from greenhouse gases and land use, 27% of the impacts for water pollution, 46% for water use and 34% for biodiversity loss.
Even low-meat diets had lower differences of at least 30% in these categories compared to high-meat.
The Oxford University team said these results mean policymakers should take action to reduce meat production and consumption.
In a Commons committee hearing on food security last week, farming minister Mark Spencer said he would prefer to see meat production made more efficient than to tell people what to eat.
He said agriculture is improving its efficiency by 1% a year and he would like to see genetically-modified cows that emit less methane.
Caroline Lucas, questioning Mr Spencer, said the Government’s disinclination towards encouraging vegetarianism is “perverse”, adding later that it has “double standards” for raising tax on sugar, tobacco and alcohol but not meat.
A Government spokesperson said: “This is not Government policy and people should make their own decisions around the food they eat.
“Achieving the net zero target is a priority for this Government, and whilst food choices can have an impact on greenhouse gas emissions, well-managed livestock also provide environmental benefits such as supporting biodiversity, protecting the character of the countryside and generating important income for rural communities.”
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