I wonder if this is also related to how humans have ruined some old forests' flora and fauna with improper replantation. Not sure where I saw this, but another article was suggesting that the way we have artificially replanted has led to less biodiversity due to every tree growing at the same time (thus limiting light and "food" for other organisms).

Of course, this wouldn't necessarily lead to a global change, but could be one of the pieces thst contribute to it. Even if we set up high-tech and efficient carbon farms, the planet will still struggle to maintain biodiversity...