We can't say that when x happens we get a mass extinction. To the extent we understand mass extinction, one has been caused by glaciation event, one has been caused by a massive climate change, and one has been caused by an asteroid. These events turn out to have no precedent.

If you're a conservation biologist in many fields, you're seeing your study subject disappear. People are in the position where they're chronicling radical decline, and that is not a position that conservation biologists want to be in.

No matter what Donald Trump says, it's clear that global warming is rapidly changing conditions on our planet.

Humans will eventually become extinct. People treat that as a radical thing to say. But the fossil record shows us that everything eventually becomes extinct. It depends what "eventually" means. But the idea that were going to be around for the rest of global history...I don't think there's any scientist who would suggest that is true. It could be millions of years from now. We may leave descendants that are humanlike.

The Earth is big. There are huge natural forces that have worked over geological time. But it turns out, when you look carefully at the geological time, you can't find anything like us.

There's this idea of shifting baselines. It was coined by a guy named Jeremy Jackson. It's the idea that every generation takes what it sees, and says, "Okay, well, that's the norm."

It may seem impossible to imagine that a technologically advanced society could choose, in essence, to destroy itself, but that is what we are now in the processnof doing.