This is because of the lower efficiency of converting grass into protein, and the slower growth of pastured animals: the longer they live, the more methane is released from their stomachs and nitrous oxide from their dung. Both are powerful greenhouse gases.212 Peas and nuts cause less global heating than chicken, which causes less than pork, which causes less than lamb and beef.213 Switching from a diet that’s high in meat to one entirely based on plants would cut the greenhouse gases from your food by 60 per cent.214
