Hi Enchilada,
I feel I'm not qualified to form an opinion on this. I do know that if climate changes occur, large animals have difficulty in evolving into a surviving species.
There are such things as transitional species which are short lived and small in numbers. These animals that provide the link don't survive long. Fossils are therefore rare.
Would the megafauna survive climate change? Prehistoric Man is also blamed for the extinction of the Mammoth.
So much to research before an informed opinion can be extrapolated.
An interesting article
Cheers Marty