Wildfires were once essential to the American West. Prairies and forests burned regularly, and those fires not only determined the mix of flora and fauna that made up the ecosystem, but they regenerated the land.
When people replaced wilderness with homes and ranches, they aggressively eliminated fire. But now, scientists are trying to bring fire back to the wilderness, to recreate what nature once did on its own.
One place they're doing this is Centennial Valley, in southwestern Montana.