Is this state of Earth possible, after humans left for a million years?
It is the year 4056 (or probably later). The rocket with the last residents of Earth just took off, because global warming and pollution couldn't be stopped nor reverted and Earth became uninhabitable. The human civilization leaves our solar system to live in space and search for a new planet to exploit. They travel on their mothership for a million years (this timespan can also be changed to get as close as possible to my desired scenario) until they decide to revisit and possibly resettle Earth.
What I want Earth to look like:
- 98% of all the landmass is wasteland/desert
- There are only two climate zones, hot and dry around the equator and cold and dry on the poles
- The two poles are some big chunks of ice, each covering about 20% of Earth's area
- Ocean level is about same as today and still contain some life down really deep, but all the streams are dead
- The atmosphere is still intact, but with more $CO_2$ and not much $O_2$ left
- There are no animals (at least not so big that a human eye can see it) and no flora
- There is no weather. Little to no wind, rain only arises and goes off over the ocean
The humans plan to terraform and repopulate earth with plants and animals they have saved on their mothership a long time ago.
Is this state of Earth possible or do I overlook some logical errors? What other effects would this state cause, which I have not considered yet?
This post was sourced from https://worldbuilding.stackexchange.com/q/146641. It is licensed under CC BY-SA 4.0.
1 answer
No.
The mass extinction you're hoping for"”no plants and only microscopic animals"”is impossible from these conditions.
At the point that humans left the planet, it was possible for animal and plant life to exist, even if it was limited to certain areas. Because otherwise, they'd be dead before they left.
Once humans were gone, they stopped their industrial activities that caused the pollution and climate change to begin with. In fact, your question implies that they stopped that stuff earlier: "global warming and pollution couldn't be stopped nor reverted." They tried but the climate had reached a tipping point. There were likely some industrial activities or fires that continued after they were gone, but that would have been a blip when you're talking about a million years.
Basically, once humans left, the Earth could begin to heal. For excellent explanations of the mechanisms here, with great detail over multiple areas, check out Alan Weisman's book The World Without Us.
Even with massive unstopped climate change, even with toxic air and water and soil, some plants and animals would survive. Mass extinction doesn't mean total extinction. It can't, not without science fiction world-killing technology.
After a million years, plants and animals would once again populate most of the Earth, land and water.
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