Eating less meat is "essential" to ensure future demand for food can be met and "dangerous" climate change avoided, experts have warned.
A study by leading university researchers in Cambridge and Aberdeen found food production alone could exceed targets for greenhouse gas emissions in 2050 if current trends continue.
Population growth and the global shift towards "meat-heavy Western diets" has meant increasing agricultural yields will not meet projected food demands for the expected 9.6 billion world population, it said.
Increased deforestation, fertiliser use and livestock methane emissions are likely to cause greenhouse gas emissions from food production to rise by almost 80%, experts from the University of Cambridge and University of Aberdeen found.
Lead researcher Bojana Bajzelj, from the University of Cambridge's department of engineering, said: "Agricultural practices are not necessarily at fault here - but our choice of food is.
"It is imperative to find ways to achieve global food security without expanding crop or pastureland.
"Food production is a main driver of biodiversity loss and a large contributor to climate change and pollution, so our food choices matter."
He added: "Cutting food waste and moderating meat consumption in more balanced diets, are the essential 'no-regrets' options."
According to the study in Nature Climate Change, current trends in food production will mean that by 2050 cropland will have expanded by 42% and fertiliser use increased by 45% over 2009 levels.
A further tenth of the world's pristine tropical forests would disappear over the next 35 years, it said.
The study's authors tested a scenario where all countries were assumed to have an "average" balanced diet - without excessive consumption of sugars, fats, and meat products.
The average balanced diet used in the study was a "relatively achievable goal", the researchers said, which included two 85g portions of red meat and five eggs per week, as well as a portion of poultry a day.
"This significantly reduced the pressures on the environment even further," they said.
Co-author Professor Pete Smith, from the University of Aberdeen, said: "Unless we make some serious changes in food consumption trends, we would have to completely de-carbonise the energy and industry sectors to stay within emissions budgets that avoid dangerous climate change.
"That is practically impossible - so, as well as encouraging sustainable agriculture, we need to re-think what we eat."
Cambridge co-author Prof Keith Richards said: "This is not a radical vegetarian argument; it is an argument about eating meat in sensible amounts as part of healthy, balanced diets.
"Managing the demand better, for example by focusing on health education, would bring double benefits - maintaining healthy populations, and greatly reducing critical pressures on the environment."