This is not science fiction. This is what happens when our system of growth and the system of nature hit the wall at once. While in Yemen last year, I saw a tanker truck delivering water in the capital, Sana. Why? Because Sana could be the first big city in the world to run out of water, within a decade. That is what happens when one generation in one country lives at 150 percent of sustainable capacity.

Image Thomas L. Friedman Credit... Josh Haner/The New York Times

“If you cut down more trees than you grow, you run out of trees,” writes Gilding. “If you put additional nitrogen into a water system, you change the type and quantity of life that water can support. If you thicken the Earth’s CO2 blanket, the Earth gets warmer. If you do all these and many more things at once, you change the way the whole system of planet Earth behaves, with social, economic, and life support impacts. This is not speculation; this is high school science.”

It is also current affairs. “In China’s thousands of years of civilization, the conflict between humankind and nature has never been as serious as it is today,” China’s environment minister, Zhou Shengxian, said recently. “The depletion, deterioration and exhaustion of resources and the worsening ecological environment have become bottlenecks and grave impediments to the nation’s economic and social development.” What China’s minister is telling us, says Gilding, is that “the Earth is full. We are now using so many resources and putting out so much waste into the Earth that we have reached some kind of limit, given current technologies. The economy is going to have to get smaller in terms of physical impact.”

We will not change systems, though, without a crisis. But don’t worry, we’re getting there.

We’re currently caught in two loops: One is that more population growth and more global warming together are pushing up food prices; rising food prices cause political instability in the Middle East, which leads to higher oil prices, which leads to higher food prices, which leads to more instability. At the same time, improved productivity means fewer people are needed in every factory to produce more stuff. So if we want to have more jobs, we need more factories. More factories making more stuff make more global warming, and that is where the two loops meet.

But Gilding is actually an eco-optimist. As the impact of the imminent Great Disruption hits us, he says, “our response will be proportionally dramatic, mobilizing as we do in war. We will change at a scale and speed we can barely imagine today, completely transforming our economy, including our energy and transport industries, in just a few short decades.”