Years of scientific analysis make it impossible to deny the effect humanity is having on the Earth’s climate. However, this raises an interesting question, posed by Alan Weisman in his book The World Without Us: what would happen to the planet if humanity vanished overnight? Which of our buildings, structures, roads, cities, household items, chemicals, art, pets and farm animals would perish soon after, and which would persevere for years without us? And how many years would these things endure? Hundreds? Thousands? Millions?
Perhaps one of the more emotionally charged questions is what would happen to animals. Amazingly, according to ornithologist Steve Hilty, at least a third of all birds on Earth might not even notice if we vanished. However, these animals are probably in the minority. Some species would vanish along with us, such as the lice which live on our hair and bodies, as well as the follicle mites which live in our eyelashes and the over 200 bacteria species which depend on us for survival. Our pet dogs would be finished off by wild predators, as would domesticated farm animals. It’s not all bad news though: with no large predators around, cows and pigs might survive on Hawaii. Some horse species have also shown to be particularly resilient, with escaped wild horses of the American Great Basin and Sonoran Desert replacing previous wild equine species in those areas.
Of course, there are also species that would flourish without us. With the downfall of our major cities, areas of natural habitats for certain species would be restored. It’s incredible to imagine that the entirety of New York City could be overcome by nature, but Weisman explores in his book the process by which this may happen. Within just two days of our sudden absence, the subway would flood completely. Manhattan was once 27 square miles of absorbent soil, now covered in concrete; but it rains no less today than it did then. Every day, New York relies on subway crews and 753 pumps to keep 13 million gallons of water from overpowering its underground tunnels. Within years, pavements all over the city would be permanently damaged by burst pipes, destabilising waterlogged structures.
But if even our cities aren’t immune to the processes of nature, have we created anything which is? There is plenty of concern today about plastic in the ocean. However, we’re still vastly underestimating the quantity, as so much of it is broken down by waves and rocks into microscopic fibres. Scientists in one study found small pieces of plastic in the digestive systems of 95% of dead birds washed up on beaches. Since pieces of plastic found in the sea are being eroded to such small sizes, the scientists suspect that very soon all living species will be consuming plastic – even zooplankton.
Even scarier is the nuclear debris we would leave behind. If we vanished tomorrow, about 30,000 intact nuclear warheads would remain on the planet. Though it is essentially impossible that any of these could detonate without human intervention, the radiation would take 250,000 years to decrease to the level of Earth’s natural background radiation. At that point, there would still remain the deadly dregs of 441 nuclear plants. In the United States alone, there’s at least half a million tons of Uranium-238, which has a half-life of 4.5 billion years. The WIPP (Waste Isolation Pilot Plant) in New Mexico contains millions of cubic feet of nuclear waste, which the US Department of Energy is legally required to warn passing hikers about for the next 10,000 years. Since human language mutates almost unrecognizably in a timespan of 500-600 years, this has created an interesting problem: what sort of sign might dissuade future humans (or indeed, other intelligent lifeforms) from approaching the site who speak or communicate in ways we can only guess at today?
As a thought experiment, the world without us reveals a lot – some of it reassuring, some of it terrifying, but all of it fascinating. All of the information in this article came from Alan Weisman’s book The World Without Us, so I recommend picking up a copy if you’d like to learn more.