I am not a person who believes in providence, or the market's invisible hand, or the balances that protect democracy, or Gaia. There are systems that are stable for long periods because of massive negative feedback. But that very feedback can turn positive under unusual situations, equalibriums can disappear and systems collapse.

I do not know whether we are going to 'fall over a cliff' and I don't think others do either. We just don't know enough. It is certainly clear to me that we are in danger, just not how much. WE DO NOT KNOW.

The planet has had periods of mass extinction before and has recovered, but the recovered biosphere was very different from the lost one. Technically we are losing species at the sort of rate that appeared during previous mass extinctions. Humans may be the 'dominant life form' that loses out this time.