I don’t think it’s OK for us to wipe out most life on earth due to us not really knowing who our specific victims are or will be out of the perhaps billions being harmed today and well into the future for many millennia by our actions today, most of whom aren’t even born yet.
However, God knows the people who are and will be suffering from the effects of our local pollution, acid rain, stratospheric ozone depletion, global warming, dead zones in water bodies, ocean acidification, resource depletion, etc. And he knows who is causing these and who is causing them more.
Cain told God he knew nothing about his brother, but I think God actually did know about Cain’s involvement in Abel’s death. And he knows what we are up to, as well.
Whether these environmental harms are sins, venial or mortal, I don’t know. I’m not a moral theologian. And yes they do seem very diffuse, with many people causing them and many “nameless-to-us” people suffering from them, so as to seem nothing to us personally, a drop in the ocean of harms. My conscience, however, tells me these harms are not only wrong, but also an injustice…that the ones suffering most from the harms are the ones who have benefitted least or will be benefitting least in centuries or millennia to come from the extravagant, profligate & wasteful lifestyles of the people today causing the harms. And I personally think this is an important enough injustice – in the top 5 – to warrant a remedy, if we value life.
Are the remedies easy? It seems daunting, which I think is why people shy away from even considering they may have a role in the problems or that there are any such problems. There is no silver bullet, and there is not a whole lot the government or charitable orgs can do to solve it on their own – tho they also have a role. Mitigation of these serious environmental harms require, as JPII said in 1990, everyone’s participation.
However, what I’ve found is that with God’s gracious help it is a light cross to bear, even a weightless and uplifting cross. To my great surprise, for the most part it also saves money – immediately for some measures, short-term for others, and long-term for others – and also improves one’s health. Not everyone can do everything on the 1000+ item list of mitigation measures, but they can do 1 thing, or maybe 10 or 20 things. It’s worth turning around, admitting we are causing problems and injustices, and taking those first small baby steps. Sort of a 20+ small (some large) step program spanning decades, the rest of our lives. And God is there to help us up when we stumble.
Is life worth saving? Sometimes I wonder, since so many are against doing so

But then the issue of injustice wakes me up and makes me realize, yes, we must do everything to save lives, esp of the innocent, or rather, to reduce our contributions that are harming and killing them.
If this can’t be fit in the top five, then I think we need a longer list.