For those who wonder about how the current and future hegemonies of the United States and China might rise and fall, consider the Mayan Empire, some of the remnants of which Mia MacDonald and I visited during our recent trip to Belize. We drove from Hopkins, about twenty miles south of Dangriga on the coast, on the picturesque Hummingbird Highway to just outside the town of San Ignacio, where, only a mile or two from the border with Guatemala were the ruins of Xunantunich and Cahal Pech.

I'm not going to give you the full history of this extraordinary and sophisticated civilization, that flourished in the time when Europeans didn't know what they were doing. What was interesting to me, aside from the impressive architecture and sophisticated masonry, and the picturesque nature of the ruins, was why this Empire within a matter of a couple of hundred years fell apart. It's a story better told in Jared Diamond's Collapse, but here's a version I heard on the trip.

From about the eighth century onwards, or so, the Mayan civilizations experienced two hundred years of drought, brought on by the deforestation they had caused in order to grow their crops to feed their cities and develop their culture. When the resources became scarce, the Mayans did what all humans do when they don't have enough of what they want: they went to war. And, when that only temporarily relieved the problem, they went to war again. Each time, the stakes got higher and the cruelty intensified. Instead of blood sacrifices to appease the gods, there were human sacrifices. Leaders got more ruthless, and ruthlessness itself became more ruthless.

Eventually, what seems to have happened is that people vanished into the forests and the cities fell apart. There was also a slow and steady die-off. The Mayan population seems to have shrunk from one million at its height to only a couple of hundred thousand by the time the Spanish arrived in the early sixteenth century. What they found were pockets of resistance, but no coordinated defence.

You look out from the ruins over the landscape of tall trees and thick undergrowth on the battlements and walls of Cahal Pech and Xunantunich, and it's hard to imagine that this was once a thriving city. I guess that's the case with all ruins. Indeed, across from my mother's house in Salisbury, England, is Old Sarum, which is layered over with Norman, Saxon, Roman, and Celtic ruins: testament to the continued efforts of civilizations to establish their permanence in the face of time, stronger enemies, and nature.

But there's something more substantial about these ruins, and the message they convey. It's now our entire planet that is like the Mayan Empire. Like the Maya of the eighth century, we are at our zenith. We look over everything we survey and see enormous prosperity. But in spite of all our science and sophistication, which, like the Mayan science of the ninth century, is the greatest of its time, it seems we still cannot see what our current rates of deforestation and resource consumption truly threatens. Unlike the Yucatan peninsula and the surrounds, it is our global civilization that is now at stake. Will we be any wiser?