NJ,
"banging on for years about reducing harmful emissions" are only words, pressure groups have no power and governments have power and that is confined within their own boundaries, but the human activity problem is supranational.
If you are suggesting negative population growth, meaning having more deaths than births then I agree that is a useful idea,but that has enormous social implications after a period of time, but also enormous financial ramifications in our global financial setup.(as the rate of growth of GDP is crucial to that system's survival)
And this rate of economic growth is the key point as it has fueled population growth AND environmental degradation.( encompassing alleged human caused climate change due to the gases their economic activities emitted)
It would have been clearer if I had said "one way is to dramatically reduce the damaging activity humans are perpetrating".
Unfortunately, I think neither of our suggestions have any hope of being implemented .