This planet has always evolved, wiping out all life as it knew it. With regards to environmental change, I assume you've all heard of the ice age etc.
We are all so self absorbed that we like to lay the blame at our own feet in thinking we can control a mass that travels around a star in a single universe.
I am glad that CFC's and HCFC's were banned in the 80's however I think people get confused thinking a somewhat depleted ozone layer equates to global warming.
We don't own planet Earth, the planet will survive without us. Humans will evolve and adapt or die out as a species.
I have no doubt that we will destroy each other through nuclear or religious war before we need to worry about environmental factors. There is always the potential for a natural disaster on a global scale such as Yellowstone erupting.
Life goes on. It may not be human life, but I am certainly not losing sleep over it, in fact, I'd quite like to be alive when we see the end of the world (as we know it).
And yes, I'm an environmentalist.