Anthropogenic degradation of the southern California desert ecosystem and prospects for natural recovery and restoration

Large areas of the southern California desert ecosystem have been negativel y affected by off-highway vehicle use. overgrazing by domestic livestock, a griculture, urbanization, construction of roads and utility corridors, air pollution, military training. exercises, and other activities. Secondary co ntributions to degradation include the proliferation of exotic plant specie s and a higher frequency of anthropogenic fire. Effects of these impacts in clude alteration or destruction of macro- and micro-vegetation elements, es tablishment of annual plant communities dominated by exotic species, destru ction of soil stabilizers, soil compaction, and increased erosion. Publishe d estimates of recovery time are based on return to predisturbance levels o f biomass, cover, density. community structure, or soil characteristics. Na tural recovery rates depend on the nature and severity of the impact but ar e generally very slow Recovery to predisturbance plant cover and biomass ma y take 50-300 years, while complete ecosystem recovery may require over 300 0 years. Restorative intervention can be used to enhance the success and ra te of recovery, but the costs are high and the probability for long-term su ccess is low to moderate. Given the sensitivity of desert habitats to distu rbance and the slow rate of natural recovery, the best management option is to limit the:extent and intensity of impacts as much as possible.