This community is pretty quiet, mostly seeming to be a place for news articles to get posted. Sadly doesn't seem to have much in the way of discussion, but that also keeps it from being infected with a lot of the issues I see elsewhere on Lemmy.
I guess that's my roundabout way of saying you're doing alright! Only Monday Memes in particular seems like a pretty good call.
Civilizations are big, and people are resilient - so we rarely find things like, "This plague/volcanic eruption/extinction of a species 100% wiped out this civilization and their culture". People tended to move away rather than just die, and their cultures tended to assimilate and combine rather than just vanish.
But there are placed where we reasonably believe that natural consequences resulted in the decline of civilizations:
The decline of the Sumerian nations is associated with increasing salinity of the fields in southern Sumeria, shifting populations north towards Akkad. I believe there's still uncertainty over whether this was driven by Sumerian irrigation practices or some other cause, but the fact that it happened is undeniable.
The Hittite Empire was a vast prehistoric empire which collapsed as part of a period of upheaval known as the Late Bronze Age collapse. The cause of the collapse is still disputed, but it is clear that there was some environmental shift involved. Warfare, plague, and economic changes may also have contributed.
In both these cases, we have only very fragmentary remnants of the surviving culture, often filtered through the lens of subsequent civilizations' recordings. The Hittites even were arguably "lost" for a time - until the mid-1800s, they were only known through Biblical references, rather than any relics or ruins.