[pegas1]

Controled burns are only a part of the solution, generally substituting for large grazing animals that would keep the forest density and undergrowth at bay. Also, a lot of wetland in Califormia was dried and even rivers were straightened and deprived of the traditional meandering and inundation area. All that makes California dryer, slowly but surely decreasing water stored in the soil and therefore also decreasing secondary rainfall (summer thunderstorms from local evapotransiration) that would keep forests less dry.