FILET mignon commands a princely sum on many restaurant menus. But bill-payers may not realise its true cost to the planet. Meat provides 17% of global calorific intake, but it requires a disproportionate amount of water and feed. And more land is given over to grazing animals than for any other single purpose. Overall the livestock sector accounts for between 8% and 18% of global emissions—about as much pollution as comes out the tailpipes of the world’s cars. Ruminant livestock, such as cattle and sheep, have stomachs containing bacteria able to digest tough, cellulose-rich plants. But along the way, huge volumes of gases are farted and belched too. The UN’s Food and Agriculture Organisation estimates that the world’s domesticated ruminants annually release 100m tonnes of methane—a greenhouse gas 25 times more powerful than carbon dioxide. Much research in recent years has looked into meat’s environmental hoofprint. A study published in the journal Proceedings of the National Academy of Sciences in 2013 presented findings on the quantities of greenhouse gases associated with producing a kilo of protein from different animals. Chicken proved the greenest meal option at 3.7kg. Pork came second with 24kg. And cattle far behind at 1,000kg. Chicken and pork proved preferable because of the efficiency of factory farming. Reports by Chatham House, a British think-tank, on diet and climate change appeared in both 2014 and 2015. The latter noted the growing share of global crops given over to animal feed and considers the effects on food prices. The desires of rich carnivores often trump the needs of poorer cereal consumers.

So what is a conscious consumer to do? A recent study also published in Proceedings of the National Academy of Sciences calculated the benefits of low-meat and no-meat diets using computer models through to 2050. The former daily regime included eating five portions of fruits and vegetables, less than 50g of sugar, up to 43g of red meat and a total energy content of between 2,200-2,300 calories. A vegetarian diet and a vegan diet were also analysed. Following a modest meat diet, global greenhouse gas emissions were found only to increase 7% by 2050 (compared with an expected increase of 51% according to projections from the status quo). A widespread switch to vegetarianism could curb emissions by nearly two thirds and veganism by 70%. More careful diets would also offer more direct health benefits. Gobbling too much red meat, particularly the processed sort, can increase the risk of heart disease and certain cancers. The study found that more than 5m deaths could be averted over the next three decades or so if meat were consumed modestly around the world. Over 7m could be saved if veggie-eating caught on more widely; 8m would benefit from popular veganism.

Controlling what meat people eat will not appeal to governments anywhere, however. And given the poor nutrition from which millions suffer any campaign against animal protein could appear misguided. According to the UN, 795m people are currently undernourished. In the developing world, richer populations will develop a growing taste for the red stuff. Global meat consumption looks set to rise by more than 75% by 2050. Managing pasture well, selectively breeding creatures and changing what they eat—forage rape and fodder beet can curb methane emissions by a quarter compared with grass and clover according to research conducted in New Zealand—could all help reduce environmental hoofprints. More simply, diners in the rich world could opt for mushroom tarts and leek risottos of their own accord.