Timber cutting also destroyed the majority of old growth trees, causing high densities of smaller and younger trees to grow in their place. Today we often think of forests being healthy when we see dense uninterrupted lush green trees. However forests in the western US were sparser previously, with regular wildfires thinning younger trees, sparing older/tougher trees, modulating forest density, and altering the mix of undergrowth/young trees/old growth. There are videos on YouTube showing comparisons of forests from 100 years ago and today, and they look very different as a result of these changes.