Reforest the oceans, shrubs and grasses are good enough for land.

Kinda hard to make male contraceptives. Women are naturally infertile for most of the time not spent actively ovulating. They are permanently infertile during pregnancy, real or synthetic. But men? We’re always churning out swimmers. When that process stops, something has gone very wrong.

So, artificially induce a naturally occurring phenomenon vs artificially terminate a constant mechanism.