Invasive species and other threats to California's biological diversity

JOHN M. RANDALL, Associate Science Director, South Coast & Deserts, The Nature Conservancy - California Chapter & Plant Sciences Department, University of California, Davis

Monday, November 09, 2009
4:00 PM - 5:15 PM
La Kretz Hall 110

California's native animals, plants, and natural communities face a variety of threats including rapid development, land use change, altered fire regimes, water withdrawl and altered hydrology, and invasive species, among others.  I will focus on just one of these threats, invasive species, and illustrate how widespread and pervasive it is geographically, across habitats, and across species of plants and animals affected.  I will also point out relationships among and synergies between invasive species and other threats such as altered fire regimes and development.  Invasive species are of concern to the conservation community not because they are non-native, but because of their harmful impacts on native species, natural communities and the ecosystem processes that support them.  Their effects range from altering ecosystem processes like fire frequency and intesity or nutrient cycling, directly feeding on and killing native species, and altering the genetic make-up of native species populations by hybridizing with them. They can also disrupt biological processes like pollination and fruit dispersal, change plant and animal community composition and structure and suppress native species populations.  Many terrestrial, freshwater and nearshore marine systems around the world are now affected by invasive species, but California has been in the forefront of experiencing this damage.  Fortunately, California has also been in the forefront of scientific studies of the ecology, effects and control of invasive species and of innovative control and prevention efforts.  Unfortunately, we remain unable to control large infestations of some of the invaders which have the most harmful impacts, such as the fire-promoters cheatgrass and buffelgrass, and the lethal plant disease Sudden Oak Death.  On the positive side, efforts to prevent the introduction of new species likely to become invasive will help slow the growth of the problem.