The US Forest Service was started in 1905 in part to reduce forest fires. The result of that policy was forests with a much higher tree density than naturally occurred otherwise.
Other changes include that around 1900 settlers of the western US introduced livestock that ate grass, which in turn removed potential fuel for smaller fires, and enabled smaller trees to grow.
After a hundred years of fire prevention, you end up with very different forest density. As the fire manager of Santa Fe National Forest noted: “On this forest, it’s averaging about 900 trees per acre. Historically it was probably about 40.” The result is a much bigger fire risk than previously.
https://unintendedconsequenc.es/morals-of-the-moment/
Other changes include that around 1900 settlers of the western US introduced livestock that ate grass, which in turn removed potential fuel for smaller fires, and enabled smaller trees to grow.
After a hundred years of fire prevention, you end up with very different forest density. As the fire manager of Santa Fe National Forest noted: “On this forest, it’s averaging about 900 trees per acre. Historically it was probably about 40.” The result is a much bigger fire risk than previously. https://unintendedconsequenc.es/morals-of-the-moment/