Synthesis of Ecosystem Resources and Threats 135 ECOSYSTEM RESTORATION ON SANTA CATALINA ISLAND: A SYNTHESIS OF RESOURCES AND THREATS Denise A. Knapp University of California, Santa Barbara Ecology, Evolution, and Marine Biology Department Santa Barbara, CA 93106-9610
[email protected] ABSTRACT: Catalina Island‘s oaks provide habitat for a diverse array of plants and animals, many of them rare. The oak ecosystem encompasses a large majority of the island, yet the foundation of this system, the oaks themselves, appear to be in decline. Seaver Institute funds allowed the Catalina Island Conservancy and its partners to initiate a variety of ecological research projects and restoration initiatives using an ecosystem-level approach. In this paper, the natural resources of the island are discussed (with an emphasis on those depending on oaks), along with the threats to those resources and natural processes. Oak habitat dominated by Quercus pacifica has declined by as much as 31 percent over the past 60+ years on the island, with no apparent recruitment into the canopy. Low moisture, poor dispersal, trampling by bison, and browsing by mule deer appear to be limiting regeneration of this species, the adults of which are likely dying due senescence (old age) hastened by stressors such as browsing by introduced ungulates. Quercus tomentella is restricted to seven locations on the island, yet maintains relatively high genetic diversity; the greatest threats to this species are likely small population sizes, fragmentation, deer browsing, and root exposure caused by erosion. A multitude of invasive, transformer species threaten the island‘s native and endemic species, along with hydrologic alteration, roads, and increased fire frequency.