A Planet in Peril: Is Earth Approaching a Tipping Point? - TIME

The Earth has never stood still. Change is built into the life of the planet, whether physical changes to the surface of the Earth — through the slow action of erosion or glaciation — or biological changes to the species that populate it. We only have to go back to the last ice age — which peaked just 20,000 years ago, a coffee break in geological time — to see a climate that is utterly different from the one human beings have thrived in for the last few thousand years. Heraclitus had it right: the only constant is change.

So it's not the fact that the global environment and the climate are changing that so worries many scientists. It's the rate of change — and whether or not human beings, and everything else that lives on the Earth, can adapt. Because the Earth, it turns out, is changing very, very fast.