“SPECIES THAT
HAVE CLOSE
BONDS WITH
HUMANITY ARE
MOST LIKELY TO
SUFFER”
microbes,” explains Weisman. “Anything that looks
delicious is going to get devoured.”
The bug explosion will in turn will fuel
a population increase in bug-eating species, like
birds, rodents, lizards, bats and spiders, and, then,
a boom in the species that eat those animals, and
so on all the way up the food chain. But what goes
up must come down – those huge populations will
be unsustainable in the long term once the food
that humans left behind has been consumed.
The reverberations throughout the food web caused
by the disappearance of humankind may still be
visible as much as 100 years into the future,
before things settle down into a new normal.
Some wilder breeds of cattle or sheep could
survive, but most have been bred into slow and
docile eating machines that will die off in huge
numbers. “I think they will be very quick pickings
for these feral carnivores or wild carnivores that are
going to start proliferating,” says Weisman. Those
carnivores will include human pets, more likely
cats than dogs. “I think that wolves are going to be
very successful and they’re going to outcompete
the hell out of dogs,” Weisman says. “Cats are a very
successful non-native species all over the world.
Everywhere they go, they thrive.”
The question of whether ‘intelligent’ life could
evolve again is harder to answer. One theory holds
that intelligence evolved because it helped our early
ancestors survive environmental shocks. Another
is that intelligence helps individuals to survive
and reproduce in large social groups. A third is that
intelligence is merely an indicator of healthy genes.
All three scenarios could plausibly occur again
in a post-human world.
“The next biggest brain in the primates per
bodyweight is the baboon’s, and you could say that
they’re the most likely candidate,” says Weisman.
“They live in forests, but they’ve also learned to live
on forest edges. They can gather food in savannahs
really well, they know how to band together against
predators. Baboons could do what we did, but, on
the other hand, I don’t see any motivation for them.
Life is really good for them the way it is.”POLLUTED PLANET
The shocks that could drive baboons (or other
species) out of their comfort zone could be set in
motion by the disappearance of humans. Even if
we all vanished tomorrow, the greenhouse gases
we’ve pumped into the atmosphere will take tens of
thousands of years to return to pre-industrial levels.
Some scientists believe that we’ve already passed
crucial tipping points – in the polar regions
particularly – that will accelerate climate change
even if we never emit another molecule of CO2.
Then, there’s the issue of the world’s nuclear
plants. The evidence from Chernobyl suggests
that ecosystems can bounce back from radiationPHOTOS: GETTY X3, SCIENCE PHOTO LIBRARY X2, ALAMYreleases, but there are about 450 nuclear reactors
around the world that will start to melt down
as soon as the fuel runs out in the emergency
generators that supply them with coolant. There’s
just no way of knowing how such an enormous,
abrupt release of radioactive material into the
atmosphere might affect the planet’s ecosystems.
And that’s before we start to consider other
sources of pollution. The decades following human
extinction will be pockmarked by devastating oil
spills, chemical leaks and explosions of varyingDomestic cats,
like these that inhabit
Aoshima Island
in Japan,will
probably do well
in a human-free
worldJune 2017 47