Animal extinctions, holes in the ozone and ocean acidification are a few examples of the enormous impact humans have had on Earth. But what would happen if humans suddenly vanished?
It’s a fun thought experiment, and Mitchell Moffit and Gregory Brown gave us their take in the latest ASAP Science video released Friday January 30.
It’s easy to imagine an empty, desolate planet with crumbling cities overrun with weeds and vines in a human-free world. But it would take a long time to reach that kind of calm equilibrium. The first few weeks without humans would be absolute chaos, according to ASAP Science.
First, power plants would fizzle out. Then, with no more electric fences to corral them, about 1 billion pigs, 1.5 billion cows and 20 billion chickens would break out of their pens in search of food. These domesticated animals are dependent on humans, so its likely that many would starve. Some would meet a more grisly fate and become food for wild dogs and cats.
Many of our prize, dog show and cat show-winning breeds are not suited for life in the wild, and more resilient mixed breeds, wolves, and wildcats would wipe them out. Rats and cockroaches would sorely miss the trash we produce, and their population would plummet. Head lice would go completely extinct.
Before plants even get the chance to overrun streets and cities, many would burn to the ground first. With no firefighters, one single lightning strike that hits a timber roof and starts a blaze could destroy a city worth of buildings. Within 100 years, most wooden structures would be gone.
Anything made out of steel, like cars and bridges, would be next to go. Without constant paint coatings, the iron in steel would react with oxygen in the air and turn to rust. Steel buildings in the desert would last much longer since there’s less moisture there to speed up rusting.
The cities that survived the fires would be overrun by weeds and vines, and eventually by larger plants and trees. Roads would turn to rivers, and underground subway systems would flood.
Most species that humans have repressed would return to the population levels they were at before humans evolved. Invasive species that humans have imported and exported would continue to thrive in their non-native lands. ASAP Science points out that it’s even possible that escaped zoo animals could thrive in their new habitat.
Think lions roaming the Great Plains, or hippos swimming in South American rivers.
Even if we suddenly disappeared, humans would leave behind some permanent traces. Electromagnetic radiation from our radios and phones will continue zipping their way through space. Our mountains of trash would also linger. The chemicals in plastics and certain types of rubber can’t be digested by bacteria and do not naturally break down.
The plastics and rubber would eventually be swept into the oceans and settle in sediment layers. After hundreds of millions of years they would integrate into rock layers and become part of the geological record.
“Alien geologists from outer space may be surprised to find sedimentary rocks full of tiny carbon-based particles that were once part of rubber tires or plastic bags,” ASAP Science says in the video.
The natural carbon cycle would return atmospheric carbon dioxide levels to normal after a few thousand years, but radioactive material from sources like nuclear power plants would stick around much longer.
These lingering human traces would be puzzling to any aliens that stumble upon our planet, but the biggest mystery would be how we suddenly disappeared off the face of the Earth.
You can watch the full ASAP Science video below:
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