SALEM, Ore. (AP) — Crews across the U.S. West are lighting controlled burns and taking other steps to prepare for the 2021 fire season that follows the worst one on record.

Prescribed burning gets rid of vegetation that can send flames into the forest canopy, where fire can spread easily, and makes the forest more fire resilient.

Last year’s fire season obliterated several towns in Oregon, caused mass evacuations in California and smothered the entire West Coast in thick brown smoke for days. All that activity, though, has barely scratched the surface.

The federal government owns roughly 640 million acres, all but 4% of it in the West, with some of it unsuitable for prescribed burning.