On my way home from dropping Sue at work this morning I was looking at all the houses, streets and factories and thinking about how different the place must look compared to what it had been like before humans came along. Then I got to thinking about what would happen if humans disappeared overnight - how long would it take before a hypothetical alien visitor couldn't tell that we had ever existed? At first I looked at the buildings and thought, "they're pretty solid. The shapes of those will surely be around for ages". And similarly with roads - the flat tarmac surface looks pretty impenetrable. But then I looked at the weeds growing in the cracks in the pavement and in the tarmac of poorly maintained roads, and also remembered what I had read and seen on telly about Roman cities in the UK (and this is true for ancient ruins everywhere) - all over the south of England there were sturdy villas, temples and civic buildings made by the Romans but by our times many of them had completely disappeared and we wouldn't know about them if archaeologists hadn't discovered them, often covered by quite deep layers of soil which must have accrued since the Romans left in 410AD.
I started thinking then about what the world, or just this little bit of it, would look like after 10 years, 100 years, a million years etc. I imagined forest taking over again, natural ecosystems re-establishing themselves in our cities, houses collapsing quite quickly once the roofs fell in and maybe after a few hundred years our towns and cities, our fields and our roads would be, on a quick inspection anyway, as if we had never existed. And after a million years? How hard would a visiting archaeologist have to look to see any trace of human civilisation?
When I got home I did a search on the internet and quickly discovered (unsurprisingly) that I am not the first person to do this 'thought experiment'. One of the first things that came up when I put in the search terms "If humans disappeared from earth" was this very interesting little video with the title "What would happen if humans suddenly disappeared?" Watching it I realised that I had not thought about what would happen to factories, nuclear power plants, sewage treatment works and garbage facilities if the power went off - the short-term impacts could be quite severe for the plants and animals that we left behind. Or maybe they wouldn't, we just don't know. I also hadn't thought about what would happen in the space around our planet - apparently all our man-made satellites would fairly quickly start to fall back to earth and burn up on re-entry to the atmosphere. After only three years, without humans to maintain it and nudge it back into a stable orbit every now and then, this would happen to the International Space Station.
So here's the link for the film - it's less than ten minutes long but it's very thought provoking.
So, have you watched it? What did you think of it?
Although it did mention potentially lasting human impacts such as nuclear waste, the Pacific Garbage Patch and the possibility of a chemical nuclear winter, there was no reference to the effect we have had on the atmosphere by the amount of CO2 we have put into it over the last 200 years. I suppose that if a chemical nuclear winter and/or a new ice age happened the current climate chaos that we have unleashed would pale into insignificance.
Another thing that wasn't talked about was the evolution of new species, not only to fill the gaps left by all the species that we have driven into extinction, but also to occupy the new niches that our existence has created - such as the cities, of course but also nuclear waste dumps, garbage-filled seas and (maybe) an ice-free Arctic.
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