There are several causes for forest fires, but once started the speed and intensity of its propogation depends on many factors.Some of these are totally beyond our control; the weather conditions (wind, temperature, relative humidity).
The lay of the land (steepness of terrain, orientation, etc.).
But there are other factors which we can control with an eye to minimizing, or even stopping, the speed and intensity of the fires devopment.
It is a question of COMBUSTIBLE MATERIAL.
The thickness, the type and the situation of the undergrowth, are determining factors in the evolution of a fire.
So we work with the forest to diminish its combustibility and make the spreading of a fire less likely.
We prune the low branches of the trees so that they are out of reach of the undergrowth (vertical continuity). We also prune the brush to reduce their size and stimulate their fruiting (junipers, aladerns, etc).
We partially eliminate bushes to avoid their contact with each other or the trees (horizontal continuity), and we totally eliminate the species that are highly combustible and of no ecological value (wild grass and weeds, etc.).
With all this we achieve:
Disminish the density of the undergrowth, the quantity of combustible material.
Select the species, eliminating those that are of no interest.
Break the continuity (horizontal, vertical) between the undergrowth and the trees.
These actions do not only slow down or, in the best of cases, stop the sreading of a fire, but also create a zone where fire fighters can safely and effectively operate to extinguish the fire.