The notion of "nature in balance" is selection bias. There are certainly places where nature is not sustainable and balanced. Look for example at what happens w

The notion of "nature in balance" is selection bias. There are certainly places where nature is not sustainable and balanced. Look for example at what happens with the introduction of invasive species (which may happen these days because of humans, but I imagine the opening of the Bering's Strait land bridge would have lead to a similar disruption.) Pre-human nature only appeared balanced because it had had a long time to equilibrate, not because of some innate quality.