Extrapolating from other organisms' "great filter" here on Earth, although on a smaller scale, I think it's overconsumption of resources. That's how you let large populations wipe themselves out and it has happened numerous times here already. It's always a problem when a population does not have a natural enemy to keep themselves in balance. If it it happens, it'll happen on a more extreme scale for us, but only because we are so influental. While a smaller population will provide us resources once again, I'm not sure an advanced society will have an easy time getting up to speed again. We wouldn't be able to build the society of today all over again from scratch since oil and ores have become too scarce -- it's built on the foundation that is was once a highly available and cheap resource requiring low tech tools for extraction.
> We wouldn't be able to build the society of today all over again from scratch since oil and ores have become too scarce
Are you sure? We don't burn iron, we concentrate it on the surface. Ruined cities would be more concentrated ore sources than any early mines could be.
Oil is harder, but you can make biogas, so it will just mean higher fuel prices.
Good point about ores. I think it's a bit of give and take there. There are many unrecycable products trashed but there's also no doubt major advantages there.
Yes, as for oil I was thinking more along the lines of being essential to produce machinery, and the problems when you end up walking up that chain all the way to the lowest common denominator, so to speak, or conversely the added costs which get added on top of each other. It would be a quite different world. I wonder what it would look like.
