I ADMIT IT. The last time my boyfriend got his hair cut, I didn’t notice. But
as unobservant as I am, you might think I’d at least notice if I was living
through both an ice age and a mass extinction on the scale of the one that wiped
out the dinosaurs.
Apparently not. I used to think I knew what scientists mean when they bandy
terms like “ice age” and “extinction”. I imagined dinosaurs choking on poisonous
gas, and snow falling in the tropics. Pretty dramatic stuff. But over free beers
at a conference in Edinburgh last month, I learned that I’ve been getting it all
wrong.
It turns out that the planet has spent a huge chunk of its life without any
ice on its surface at all—not even at the poles. The climate goes through
long cycles, generally determined by astronomical phenomena such as the tilt of
the planet and its proximity to the Sun. Over the past billion years, the Earth
has spent just five per cent of the time in three isolated chilly bits when
glaciers romped back and forth over the continents.
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We’re in the most recent of those ice ages now. People in 17th and
18th-century England may have noticed this when they found they could skate on
the Thames and light bonfires on it without falling through. We’re still so
close to these kinds of conditions that some claim our greenhouse-gas binge has
actually saved us from slipping back into the freezer. In all probability, we
have millions of years left before the ice age technically ends and we can throw
out our woolly jumpers.
As for the extinction bit, I knew about the dodo, but I had no idea that
humans are currently facilitating the death of between 20,000 and 100,000
species every year. That’s a lot, considering that estimates of how many species
we share the planet with range from 2 million to 100 million.
That puts us smack in the middle of the sixth great killing spree of the past
300 million years. Richard Leakey and Roger Lewin wrote a book about this
frightening decline: it’s called, not surprisingly, The Sixth
Extinction. We can argue about the numbers, but the point is clear. Because
we do silly things like hunting, introducing rabbits to Australia, pouring toxic
gunge into the ocean and cutting down loads of trees, animals are dying at about
the same rate as if fate had chucked a giant asteroid at us.
I always thought we were living in a normal, in-between part of the Earth’s
history (apart from the fact that there are humans roaming around). But we’re
not. We are on an unusually icy page of the history book, with animals dropping
dead all around us.
It makes me wonder what else I haven’t noticed.