Science-based invasive plant management on the California Channel Islands

Invasive species are the leading cause of species extinctions in island ecosystems; the California Channel Islands are no exception. All eight Channel Island floras include a significant proportion of non-native invasive plant taxa, and control measures have been implemented to differing degrees on each island to address these threats. In 1992 following the removal of cattle and feral sheep from Santa Cruz Island, and in combination with record levels of precipitation during an “El Nino year,” Foeniculum vulgare (fennel) expanded exponentially throughout the Island. Learning from this situation, the Catalina Island Conservancy initiated a science-based invasive plant program in 2003, including an island-wide invasive plant survey, species and site prioritization, and program implementation after successfully eradicating feral goats and pigs on Catalina Island. The program has led to the active eradication of 25 plant species during their invasion phase, and the reduction of five widespread priority species from key watersheds on Catalina Island. In 2007, The Nature Conservancy on Santa Cruz Island adapted its science-based program from the program implemented on Catalina Island by increasing speed and efficiency through the utilization of a helicopter in both species survey and eradication efforts. Both programs base management objectives on scientific data and ecological processes and function, thus allowing for defendable management decisions to be made.