We are living at the dawn of a new epoch in the history of the Earth: the Anthropocene.
Humans have always shaped aspects of their environment, from fire to agriculture. But the influence of Homo sapiens on Earth has reached such a level that it now defines current geological time.
From air pollution in the upper atmosphere to plastic fragments at the bottom of the ocean, it’s nearly impossible to find a place on our planet that humanity hasn’t touched in some way. other. But there is a dark cloud on the horizon.
Well over 99% of the species that have ever existed on Earth became extinct, most in cataclysms and the kind of extinction events that killed the dinosaurs.
Humanity has never faced an event of this magnitude, but sooner or later we will.
The end of humanity is inevitable
Human extinction, according to many experts, is not a matter of “if”, but of “when”. And some believe it will come sooner rather than later. In 2010, the eminent Australian virologist Frank Fenner claimed that humans will likely disappear in the next century due to overpopulation, environmental destruction and climate change.
Of course, the Earth can and will survive just fine without us. Life will persist and the marks we left on the planet will fade faster than you think. Our cities will crumble, our fields will sprout and our bridges will fall.
“Nature will eventually destroy everything,” says Alan Weisman, author of the 2007 book The World Without Us, which examines what would happen if humans disappeared from the planet. “If he can’t break things down, he ends up burying them. »
Before long, all that will be left of humanity will be a thin layer of plastic, radioactive isotopes and chicken bones – we kill 60 billion chickens a year – in the fossil record. For proof of this, we can look to the areas of the planet that we have been forced to leave.
In the 19-mile exclusion zone surrounding Ukraine’s Chernobyl power station, which was badly contaminated after the 1986 reactor meltdown, plants and animals are thriving like never before.
Animals, like this adventurous cat, have reclaimed the Chernobyl Exclusion Zone since humans moved away ©Getty Image
A 2015 study funded by the Natural Environment Research Council found ‘abundant wildlife populations’ in the area, suggesting humans are far more of a threat to local flora and fauna than 30 years of chronic exposure to radiation.
The speed at which nature reclaims a landscape depends very much on the climate of a region. In the deserts of the Middle East, ruins from thousands of years ago are still visible – but the same cannot be said for cities only a few hundred years old in the rainforests.
In 1542, when Europeans first saw the rainforests of Brazil, they reported towns, roads and fields along the banks of major rivers. However, after the population was decimated by diseases brought by explorers, these towns were quickly reclaimed by the jungle. The ruins of Las Vegas are certain to persist much longer than those of Mumbai.
Trees and roots take over the Ta Prohm temple in Cambodia © Getty Images
Only now are deforestation and remote sensing techniques offering us a glimpse of what came before.
Plant and animal species that have formed close ties with humanity are most likely to suffer if we disappear.
The crops that feed the world, which depend on regular applications of pesticides and fertilizers, would quickly be replaced by their wild ancestors.
“They’re going to be overwhelmed, quickly,” Weisman says. “Carrots will become Queen Anne’s lace again, corn could become teosinte again. The original ear of corn that wasn’t much bigger than a stalk of wheat. »
Regeneration of a food chain
The sudden disappearance of pesticides will also mean an explosion in the insect population.
Insects are mobile, reproduce quickly and live in almost any environment. Which makes them a very successful class of species, even when humans are actively trying to suppress them.
Much like these Roman ruins, today’s buildings would still be recognizable in the future ©Getty Images
“They can mutate and adapt faster than anything else on the planet, except maybe microbes,” Weisman says. “Anything that looks delicious is going to be devoured. »
The explosion of insects will in turn fuel an increase in the population of insect-eating species. Like birds, rodents, reptiles, bats and arachnids. Then a boom in species that eat these animals, and so on up the food chain.
But what goes up must come down. These huge populations will not be viable in the long term once the food left behind by humans has been consumed.
The repercussions throughout the food web caused by humanity’s demise may still be visible up to 100 years in the future. Before things stabilize in a new normal.
Some wilder breeds of cows or sheep might survive. But most were raised in slow, docile eating machines that will die in large numbers.
“I think they’ll be very quick pickings for these wild carnivores that will start to proliferate,” Weisman says.
When humans leave the planet, insects will experience a rapid renaissance ©Getty Images
These carnivores will include human pets, more likely cats than dogs. “I think wolves are going to be very successful and outperform dogs,” Weisman said.
“Cats are a very thriving non-native species around the world. Wherever they go, they thrive.
The question of whether “intelligent” life could evolve again is more difficult to answer. One theory holds that intelligence evolved because it helped our early ancestors survive environmental shocks.
Another is that intelligence helps individuals survive and reproduce in large social groups.
Cats are predicted to fare better than dogs in the event of human extinction ©Getty Images
A third is that intelligence is just an indicator of healthy genes. All three scenarios could presumably play out in a post-human world.
“The second largest primate brain by body weight is that of the baboon. And you could say he’s the most likely candidate,” Weisman says.
“They live in the forests but they have also learned to live on the edge of the forest. They can harvest food very well in the savannahs, they know how to group together against predators. The 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 as it is.
The future of life on a polluted planet
The tremors that could push baboons out of their comfort zone could be triggered by the disappearance of humans.
Even if we all disappeared tomorrow, the greenhouse gases we released into the atmosphere will take tens of thousands of years to return to pre-industrial levels.
Some scientists believe that we have already passed crucial tipping points. In the polar regions in particular. Which will accelerate climate change even if we never emit another molecule of CO2. Then there is the issue of nuclear power plants around the world.
Evidence from Chernobyl suggests that ecosystems can recover from radiation releases. But there are about 450 nuclear reactors in the world that will start melting down. And this, as soon as the fuel runs out in the emergency generators that supply them with coolant.
A coal fire burns underground in Centralia, Pennsylvania © Getty Images
There is simply no way of knowing how such a huge and sudden release of radioactive material into the atmosphere could affect the planet’s ecosystems.
And that’s before we start looking at other sources of pollution.
The decades following human extinction will be marked by devastating oil spills. Chemical leaks and explosions of various sizes. All ticking time bombs humanity has left behind. Some of these events could cause fires that could burn for decades.
Beneath the town of Centralia in Pennsylvania, a seam of coal has been burning since at least 1962, forcing the evacuation of the local population and the demolition of the town.
Today the area appears as a prairie with cobbled streets running through it. With plumes of smoke and carbon monoxide emerging from below. Nature has reclaimed the surface.
The last traces of humanity
But some traces of humanity will remain, even tens of millions of years after our end. Microbes will have time to evolve to consume the plastic we left behind.
Roads and ruins will be visible for many thousands of years. But will eventually be buried or broken by natural forces.
It is reassuring to know that our art will be one of the last proofs of our existence. Ceramics, bronze statues and monuments like Mount Rushmore will be among our most enduring legacies.
Our emissions too: the Earth has been transmitting its culture by electromagnetic waves for more than 100 years. And these waves propagated in space.
Assuming no collisions, the Voyager space probes will even survive our planet ©Getty Images
Thus, at 100 light-years, with a sufficiently large antenna, you will be able to pick up a…
