Listen, there is no sense in cleaning up the place if the aliens are just going to take it over anyways. We might as well leave the problem in their hands. If they want the mess, they can have it.
Seriously, in 40 years a lot can happen. But its not going to miraculously happen on its own, I think the time frame is reasonable if someone is actually going to pro-actively do something about it.
If not, then hell, we might not make it that far anyways, so whats the worry?
