THE Earth is a big thing; (click here) if you divided it up evenly among its 7 billion inhabitants, they would get almost 1 trillion tonnes each. To think that the workings of so vast an entity could be lastingly changed by a species that has been scampering across its surface for less than 1% of 1% of its history seems, on the face of it, absurd. But it is not. Humans have become a force of nature reshaping the planet on a geological scale—but at a far-faster-than-geological speed.
A single engineering project, the Syncrude mine in the Athabasca tar sands, involves moving 30 billion tonnes of earth—twice the amount of sediment that flows down all the rivers in the world in a year. That sediment flow itself, meanwhile, is shrinking; almost 50,000 large dams have over the past half- century cut the flow by nearly a fifth. That is one reason why the Earth's deltas, home to hundreds of millions of people, are eroding away faster than they can be replenished.
Geologists care about sediments, hammering away at them to uncover what they have to say about the past—especially the huge spans of time as the Earth passes from one geological period to another. In the same spirit they look at the distribution of fossils, at the traces of glaciers and sea-level rises, and at other tokens of the forces that have shaped the planet. Now a number of these scientists are arguing that future geologists observing this moment in the Earth's progress will conclude that something very odd was going on.
The carbon cycle (and the global warming debate) is part of this change. So too is the nitrogen cycle, which converts pure nitrogen from the air into useful chemicals, and which mankind has helped speed up by over 150%. They and a host of other previously natural processes have been interrupted, refashioned and, most of all, accelerated (see article). Scientists are increasingly using a new name for this new period. Rather than placing us still in the Holocene, a peculiarly stable era that began only around 10,000 years ago, the geologists say we are already living in the Anthropocene: the age of man....
Because it has a name, doesn't make it okay.
