Without fires burning through the forest on a regular basis, the undergrowth gets too thick. So when it does catch fire, it burns much hotter. Forest fires are a natural thing. And established trees survive them. Unless the fire burns hot enough to burn the established trees. Humans carelessly starting forest fires (for the most part) kept the undergrowth down and kept the forests that much healthier. Also the forest service extinguishing both natural and man made forest fires as quick as possible, allowed the undergrowth to build up. Now when there's a fire, it completely destroys the forest. Even trees that have stood for hundreds of years. And once a fire gets going, it spreads and spreads. Because there are no natural firebreaks where a fire burned through an area years before and burned up all the fuel. Then there's the health of the forest. With the undergrowth getting too thick, it takes too much of the nutrients out of the soil, killing the trees. Some tree's seeds will only germinate after a small fire. Forest fires are a natural thing that forests evolved around. Then man started messing with nature, trying to do what they thought was best, and things got all fucked up. Add in that people now think that all fires are bad, and the forest service can't do controlled burns without people freaking out. In the end, the intent was a good and noble one. They were trying to save the forests. But the result is that they killed the forests. Sorry for the rambling. I think I repeated myself about ten times there.