The destruction of the Megafauna was an understandable mistake by our ancestors. They then learnt how to compensate for that loss using fire. Here's a nice article on how native Australians did that: https://www.abc.net.au/news/2021-05-11/historic-photos-guide-indigenous-burning-great-sandy-desert/100083720.
Global warming seems to start earlier than one would expect at the start of the Industrial Revolution. Of course a lot of other stuff was going on around the world at that time. One thing was whaling on a huge scale. Well it turns out that whale poo is an important fertiliser in the ocean, and dead whales carry a lot of carbon to the ocean floor. The whales will come back in a few centuries, but meanwhile we need to do their job to get the oceans full of fish again: https://www.nextbigfuture.com/2018/01/iron-fertilization-of-the-ocean-is-as-natural-as-whale-poop-and-it-can-save-the-planet.html.
And as in my previous post (https://grampsgrumps.blogspot.com/2021/04/the-plan-to-revive-mammoth-steppe-to.html), the megafauna were important in sequestering carbon in the Arctic, and replacement is not impossible.
Update: Another great video with stuff I didn't know about humans compensating for problems: https://youtu.be/cfl7mSG13e0. In this case, Thiamine deficiency in wild animals and fish, probably not related to megafauna extinction.
Update 2022-06-11: https://youtu.be/i4Hnv_ZJSQY is unbelievable. But it is even more unbelievable that this important solution to climate change and feeding the world has not been pursued. CSIRO was interested: https://www.abc.net.au/news/2021-12-19/volcanic-eruptions-provide-the-oceans-with-essential-nutrients/100711580, I hope they still are.
There was silly research that showed that phytoplanton take up carbon, but it all gets released when they die, so fertilization doesn't work. Of course many phytoplankton don't get to die of old age, and as their predators (and their predators, etc) defecate and later die, then a significant amount of carbon goes to the ocean floor. This video explains how some of that happens: https://youtu.be/Yo-AdMHu2ec.
