We'll probably just continue existing policy, which actually is fairly environmentally sound.

If you eliminate the middle class, they can't buy SUVs and take jet aircraft on vacations. Check.

If you eliminate industrial sites, they can emit greenhouse gasses. Check. Public policy for decades. See above, temporarily we've outsourced our middle class purchasing to Chinese factory production, but once we get rid of the middle class and return the USA to our agrarian roots, the factories in China will also close.

If you concentrate all capital and property ownership into a Very small, optimistically well educated group or individuals or corporations, they will have better chance of enlightened self interest than if the general population is permitted private property. Check, thats been public policy for decades.

Impoverish young people to discourage children, permanently lowering environmental load. Check. Public policy for decades.

I could go on about health care and homelessness and the highest prison population on the planet, but it all aligns quite well.

Honestly, we're already doing so much for the environment I don't know what more we can do without "extreme" measures.