What does a “resilient” forest look like in the Sierra Nevada? A lot fewer trees than we’re used to, according to a study of frequent-fire forests from the University of California, Davis. More than a century ago, Sierra Nevada forests faced almost no competition from neighboring trees for resources. The tree densities of the late 1800s would astonish most Californians today. Because of fire suppression, trees in current forests live alongside six to seven times as many trees as their ancestors did — competing for less water amid drier and hotter conditions.