There are now twice as many people as 50 years ago. But, as EO Wilson has argued, they can all survive in cities
Discussing cities is like talking about the knots in a net: theyre crucial, but theyre only one part of the larger story of the net and what its supposed to do. It makes little sense to talk about knots in isolation when its the net that matters.
Cities are part of the system weve invented to keep people alive on Earth. People tend to like cities, and have been congregating in them ever since the invention of agriculture, 10,000 or so years ago. Thats why we call it civilisation. This origin story underlines how agriculture made cities possible, by providing enough food to feed a settled crowd on a regular basis. Cities cant work without farms, nor without watersheds that provide their water. So as central as cities are to modern civilisation, they are only one aspect of a system.
There are nearly eight billion humans alive on the planet now, and thats a big number: more than twice as many as were alive 50 years ago. Its an accidental experiment with enormous stakes, as it isnt clear that the Earths biosphere can supply that many peoples needs or absorb that many wastes and poisons on a renewable and sustainable basis over the long haul. Well only find out by trying it.