Eating meat is bad for the environment, of that there is no doubt. And the moral arguments against killing animals are compelling. Humans currently slaughter about 1,600 mammals and birds every second for food – that is half a trillion lives a year, plus trillions more fish, crustaceans and molluscs. The total biomass of all the world's livestock is almost exactly twice that of humanity itself. And while crops that feed people cover just 4% of the Earth's usable surface (land that is not covered by ice or water, or is bare rock), animal pastureland accounts for a full 30%. Our meat, in other words, weighs twice as much as we do and takes seven times as much land to grow.
And we are going to have to feed a lot more people in the coming decades. The world's population stands at a little over 7bn; by 2060 this will have risen to perhaps 9.5bn, and that is a fairly optimistic scenario. Not only are there more and more of us, but we are eating more and more meat. Demand for it is expected to double by 2050. The market in chicken, pig, cattle and sheep flesh is worth about $1trn a year. By mid-century this will more than double, perhaps triple at today's prices, as the cost of land rises.
This is bad news for the Earth. Meat production accounts for about 5% of global CO2 emissions, 40% of methane emissions and 40% of various nitrogen oxides. If meat production doubles, by the late 2040s cows, pigs, sheep and chickens will be responsible for about half as much climate change impact as all the world's cars, trucks and aircraft.