Hate to rain on the gloom and doom parade here, but to paraphrase Mark Twain "The rumors of the death of the human species are greatly exaggerated".
Have we spoiled our environment? Yup, no two ways about it.
Will the environment recover? Eventually, but it will take on the order of several hundred if not thousand years.
Will we have to make some adjustments? Absolutely. To paraphrase Locutus of Borg "Our lives, as they have been, are over."
Are a lot of people going to die because of this? Before we finally figure all of this stuff out, probably so.
Are we going to go extinct? Not a chance, IMO.
Look, we've had the capability to completely obliterate the planet for the better part of 4 decades, and we've managed not to yet. I actually find that hopeful. We are starting to grasp that we not only have an impact on the environment, but we also have a role IN it. I also find that hopeful.
While I realize it is currently the fashionable thing to predict the demise of humanity, people keep forgetting one thing; humans are survivors. We do it better than almost any other species.
Why do I say that? Well, I mean look at us! We've no natural weapons worth a damn, our skin is relatively soft, and we've basically no fur to protect us from the weather. We've a terrible sense of smell, and an only slightly better sense of hearing (although our eyesight is pretty good). Our bodies require protein from meat that we aren't equipped to hunt, but need more calories and nutrients in an average day than we can normally acquire by eating nothing but vegetation. By all rights, we should have died out AT LEAST 100,000 years ago if not more. We should be nothing more than an evolutionary footnote; a failed experiment. And yet here we are.
So no, I don't think we are going to go extinct, but things ARE going to get tough for a while.