I have in the past pointed to the projected growth of the global population – from seven billion to 11 billion by 2100 – as a major environmental problem. But a bigger population crisis, from the ecological point of view, concerns not humans but farm animals, whose numbers are growing twice as fast. Raising livestock requires a vast amount of resources, and 75% of the world’s farmland; a third of all cereal crops are used to feed them. Livestock farming creates 14% of all greenhouse emissions – more than cars, trains, planes and ships combined. And the “tide of slurry” they produce is overwhelming the world’s capacity to absorb it. Factory farms in the US generate 13 times more waste than the US human population.

The moral is clear: if we were to eat less meat and dairy, our environmental impact would be slashed overnight. George Monbiot writes, “But while plenty in the rich world are happy to discuss the dangers of brown people reproducing, the other population crisis scarcely crosses the threshold of perception.” (Based on an article by Monbiot in The Guardian)