Most the time it is either because humans think it would be cool to burn down the forest, but it really isn't most the animals will die only some can run from it. The other way a forest fire can happen is when there is lightning and it hits the forest the forest catches on fire.....
of course fires can happen anywhere a wild fire is just a fire that is out of control.
the fire will go out.
Windscale fire happened in 1957.
Dome Fire happened in 1996.
Return Fire happened in 1995.
Laguna Fire happened in 1970.
Trigo Fire happened in 2008.
Ballantyne's fire happened in 1947.
Star Fire happened in 1979.
Heli Fire happened in 1980.
Rattlesnake Fire happened in 1953.
Chariots of Fire happened in 1924.