You're not getting it. With global environmental catastrophe the concern is not about the deaths of millions of people. It is about the deaths of all people everywhere. A symptom of the problem of environmental catastrophe is those that are cavalier about the deaths of entire species of wildlife. The planet will be fine, the plant and wildlife will recover... though it may not be the same plant or wildlife. But once humans are gone, there is very little change we are coming back. So, to be clear, though humans have and are making he planet uninhabitable for myriad of species, reducing the available variety of species, which we, in fact, depend on... it is a web... but we are also making the planet uninhabitable for people.
Serious and monumental efforts in conservation of plant and wildlife and habitat is a damn good place to start. The more natural habitat there is, the more plant and wildlife there is, the better it will be for us. First thing is first... the oil industry and the chemical industry needs to go away within the next 10 years. Government, which people control, needs to make all that crap unprofitable. All pollution must cease, and we need to figure out how to clean up what has been done. Let's not bitch about energy, nor evangelize nuclear power. Let's just bite the bullet for a few generations and force everything and everyone to generate their own energy, and require that it be clean.