You are aware that mankind has subjected itself to avoidable suffering for as long as we could swing a stick, right? We have hundreds of millions suffering (avoidably might I add) right now and even if we somehow managed to keep Earth squeaky clean - I see a lot more avoidable suffering for the millennia to come.

If anything, significantly reducing Earth's capacity to sustain humans may paradoxically result in diminished total human suffering (average suffering x number of humans) due to lower population.

For what it's worth I do care, courtesy to my overly empathetic neural wiring. I'd argue that I am doing a lot more than my peers to reduce future human suffering simply by not contributing to the overpopulation. Not that any of it matters in the grand scheme of things ;)

Keep fighting the good fight, I admire your zeal!