One of the many points the “tecchies” out there miss, that has been pointed out repeatedly by the old naturalists, is that the Chaparral plant community 'creates' moisture. There is almost no runoff from chaparral sites, and the soil only becomes dry on 'real' drought years. Most of the time soil moisture ranges from moist (not wet) to slightly dry. This is a great growing bed for the oaks, pines and trees of higher rainfall areas. The higher the brush gets, the more blowing fog or clouds are caught, and the more fog is created from this catch and release.
Chaparral is far from uniform so it is not possible to 'connect the dots'. I've drawn out the areas that could be in the range of the Chaparral plant community.
There's been a push by fire departments and insurance companies to remove Chaparral in urban interface areas. Here are some points to ponder.
Firemen don't usually die in brush fires, they die in grass
fires. Weedy fields burn faster than you can drive, never mind run. By
the time you figure out a grassy area is burning, it is over. It's like
standing in the middle of a tunnel with a high speed train coming.
Remove the alien, annual grasses and weeds; manage the native brush.
To repeat (ad nauseum!), there is almost no erosion in clean Chaparral; there are large mud slides in areas of Chaparral that have been converted to grass. In the large lysimeter study that was done at San Dimas, California, the conclusion was: removing brush would lead to enormous erosion problems. But fire insurance commonly doesn't cover mud slides....