Discussing cities is like talking about the knots in a net: they’re crucial, but they’re only one part of the larger story of the net and what it’s supposed to do. It makes little sense to talk about knots in isolation when it’s the net that matters.
Cities are part of the system we’ve 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. That’s 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 can’t 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 that’s a big number: more than twice as many as were alive 50 years ago. It’s an accidental experiment with enormous stakes, as it isn’t clear that the Earth’s biosphere can supply that many people’s needs – or absorb that many wastes and poisons – on a renewable and sustainable basis over the long haul. We’ll only find out by trying it.
Right now we are not succeeding. The Global Footprint Network estimates that we use up our annual supply of renewable resources by August every year, after which we are cutting into non-renewable supplies – in effect stealing from future generations. Eating the seed corn, they used to call it. At the same time we’re pumping carbon dioxide into the atmosphere at a rate that is changing the climate in dangerous ways and will certainly damage agriculture.
This situation can’t endure for long – years, perhaps, but not decades. The future is radically unknowable: it could hold anything from an age of peaceful prosperity to a horrific mass-extinction event. The sheer breadth of possibility is disorienting and even stunning. But one thing can be said for sure: what can’t happen won’t happen. Since the current situation is unsustainable, things are certain to change.
Cities emerge from the confusion of possibilities as beacons of hope. By definition they house a lot of people on small patches of land, which makes them hugely better than suburbia. In ecological terms, suburbs are disastrous, while cities can perhaps work.
The tendency of people to move to cities, either out of desire or perceived necessity, creates a great opportunity. If we managed urbanisation properly, we could nearly remove ourselves from a considerable percentage of the the planet’s surface. That would be good for many of the threatened species we share this planet with, which in turn would be good for us, because we are completely enmeshed in Earth’s web of life.
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.