[Emilio Romero (OP)]

In some way or another, nature/life demands and/or creates a balance. Almost everything in the world works –to a very important point— in the principle of equilibrium.
Thus nature gave speed to the gazelle to escape from the lion; it gave venom to the snake, camouflage to the seahorse, mimicry to certain octopuses, mutating ability to some viruses, foul odor to the skunk, antibiotic resistance to some bacteria... furthermore, it “creates” earthquakes to relief tension of tectonic plates, and volcanoes erupt when no more magma can be hold in... (etcetera...)
So, it can be argued that nature always finds a way to --or at least attempts-- to generate that balance, albeit it sometime takes long and complicated processes.

With those points in mind, what is nature/life/the planet going to do against us humans for all the imbalance we have brought? How long do we have before it starts happening?

I understand that global warming may be a tempting answer here, but asides from that (which, by the way, is just a consequence), let’s dig deeper... you scientists are way better than just that answer.
So, what is the venom (or the speed, or the resistance) of the planet going to be against us, and do we stand a fighting chance?

Regards
emilio

[Karsten]

Planets don't "do" anything. Nature does not "attempt" anything. If we are as much of a problem as it seems to some, we will balance ourselves within the available environment. The question is how rough it will be and for whom.

[RD]

This is what the author of the Gaia hypothesis, (Earth a single self-regulating organism), thinks is going to happen.

[Don_1]

Man will probably prove to be his own nemesis. Overcrowded cities and overpopulation as a whole coupled with global travel (personal, goods and food) has already seen the fast spread of diseases from The Black Death (Bubonic Plague) to influenza, HIV etc.

Sooner or later a new, mutant or existing incurable disease could be spread around the world. Such situations have already been the subject of many fictional disaster films. But this is the kind of fiction which can so easily turn to fact.