Here I’m referring to the plan EO Wilson has named Half Earth. His book of the same title is provocative in all the best ways, and I think it has been under-discussed because the central idea seems so extreme. But since people are leaving the land anyway and streaming into cities, the Half Earth concept can help us to orient that process, and dodge the sixth great mass extinction event that we are now starting, and which will hammer humans too.

The idea is right there in the name: leave about half the Earth’s surface mostly free of humans, so wild plants and animals can live there unimpeded as they did for so long before humans arrived. Same with the oceans, by the way; about a third of our food comes from the sea, so the seas have to be healthy too.

At a time when there are far more people alive than ever before, this plan might sound strange, even impossible. But it isn’t. With people already leaving countrysides all over the world to move to the cities, big regions are emptier of humans than they were a century ago, and getting emptier still. Many villages now have populations of under a thousand, and continue to shrink as most of the young people leave. If these places were redefined (and repriced) as becoming usefully empty, there would be caretaker work for some, gamekeeper work for others, and the rest could go to the cities and get into the main swing of things.