
Any species left unchecked will expand beyond what its environment can sustain. It turns out humans are no different than any other animal. We are quite indigenous and behave predictably.
Our numbers will increase until we have stressed our environment beyond all capacity, then we will have a sudden and quick die off and, in all likelihood, will completely destroy our species in the process.

The distress we stir on this Earth may be due to the fact we don't belong here.
darkbeaver,
That is how I've felt about it for decades, and although some have agreed jokingly, I have seen how alien we feel to this environment. I wonder, tough, if aboriginal peoples living in harmony with their environment have exhibited this pattern?
I have lived in BC since '72 and I have witnessed the wholesale slaughter of our forests and most of the wildlife that depends on it. Only a species out of tune with its environment could possibly do something that stupid, unless we are trying to recreate the atmosphere of our home planet.
That should rile up the loggers on here!

or here's the optimistic prediction:
humans realise they screwed up things on earth and start up civilisations elsewhere in the solar system, where they live in a more sustainable manner and continue to spread out through the galaxy in a star-trek-like fashion