This planet can't protect us forever. Sooner or later, there'll be a catastrophe that renders this world uninhabitable for humans. And when that day comes, we'll need to know already how to live in space.
Yesterday, we explained why we should reboot the Biosphere 2 projects of the 1990s. There are a lot of scientific and technological benefits from learning to create self-sustaining habitats — but the biggest reason is because we need to know how to live in space, before we have noplace else to live.