We live in the Anthropocene, as some scientists have come to
call our new geologic era. The term acknowledges the fact that
human beings—nearly 7 billion strong and growing—have so much
influence over the life, geography and even chemistry of planet
Earth that we’re now essentially responsible for the whole show.
For good and for ill, the planet from now on will be what we
make of it. But just because our actions are shaping the future
of the planet—and everyone and everything else that rides on
it—doesn’t mean that we always know the effects of what we’re
doing. Case in point: in a new review in the July 14 Science, a
group of researchers persuasively argue that one of the biggest
impacts that human beings have had on the planet isn’t
necessarily deforestation or climate change or pollution. It’s
the extirpation—through hunting, habitat loss or disease—of apex
predators, species like tigers or wolves or sharks that skit
high on the food chain. When those species go, there can be
drastic knock-on effects for