On the other hand when damaging the environment bet on living humans doing more harm than dead humans. The best thing for the environment would be the utter annihilation of humanity - a rather destructive process. Mind you I'm not going to make bets about that...
I don't know what it means for something to be good for an environment in the absence of people living in that environment.
Perhaps you mean that wild animals (say mammals) would be better off. Many domesticated animals arguably have lives not worth living so would be better off. However, many partially domesticated animals would be worse off; think of the rats in New York City, for example.
A reminder for everyone: on this day in 1983, Stanislav Petrov saved the world.
It occurs to me this time around that there's an interesting relationship here - 9/26 is forgotten, while 9/11 is remembered. Do something charitable, and not patriotic, sometime today.