Well, in some cases, much of the life on earth went extinct. It's also not clear how long it took to make earth a good place to live again. The planet's ecology

Well, in some cases, much of the life on earth went extinct. It's also not clear how long it took to make earth a good place to live again. The planet's ecology might be able to "heal" the damage we're doing, but it's probabably more on the scale of centuries or millenia, than decades.