The Earth doesn't need us, we are the ones who need earth - the way it is today. Period.
We might deplete all the resources on earth, we might leave it a mess, but eventually irrespective of whether mankind survives or not in the next 500 years, the earth will continue - after all it existed for 4.5 billion years and the entire existence of homo sapiens has been barely a wink in that period - a mere 200,000. No matter what we do, the earth will shrug off all what we did in a few million years. It's seen far more dominating species (dinosaurs and trilobytes were dominating species for many million years in their own time)and the earth has erased all traces of them in good time. Humankind might be destructive, but more than destroying earth, it will be destroying itself if humankind doesnt get its act together.
If we need to survive as a species for the next 500 years, we need to do much more than we do today to sustain those resources that earth provides us and which we cannot do without. And yeah, we would probably need to find our way to create colonies in outer space, in a different galaxy perhaps, that is today not within the reach of science.