Invasive Species in California State Parks
One of the central components of our State Parks mission is to preserve representative examples of California’s native ecosystems and native species diversity. Landscapes invaded by non-native invasive species do not portray an accurate view of natural California. Released from the control of their natural predators back home, some introduced species have spread, become invasive and, depending upon the species, cause a variety of problems in California ecosystems.
Introduced for practical purposes or by accident, non-native plants can wreak havoc on ecosystems, interfering with the complex interdependent relationships between native plants and animals. Non-native plants can outcompete native species for space, water, and soil nutrients, crowd out native plants, shade them from sunlight, and/or produce substances that inhibit their growth. Non-natives can also increase the frequency or intensity of wildfires and cover trails and waterways, affecting human safety, recreational opportunities and scenic values. Some examples include the eucalyptus tree that spreads along coastal stream canyons, Cape ivy that can completely cover native vegetation, iceplant that changes coastal dune species composition, and the spiny yellow starthistle which is invading more acres of California grasslands each year.
While some non-native plants such as introduced annual grasses have spread from one end of the state to the other, making effective control unachievable, other species that are less widespread and are in the process of changing ecosystems can be tackled. For over 30 years State Parks has taken aggressive action to control or eliminate the most serious invasive plants. Control methods include hand or mechanical removal, prescribed burning, and herbicides when other methods are inadequate. Experiments have been made with biological control, and Integrated pest management principles are used to find the most effective and least environmentally damaging treatments. An Early Detection, Rapid Response (EDRR) pilot program has been initiated to help detect new invasive plant introductions when populations are small, and State Parks partners with the California Invasive Plants Council (Cal-IPC) and other agencies and organizations in regional early detection collaborations.
Introduced animals came with the first European settlers to the state and newcomers continue to arrive. These non-native species either escaped or were released, sometimes by irresponsible pet owners, or more often for specific purposes such as enhanced hunting and fishing opportunities. Exotic animals can be aggressive competitors, consuming food and water resources and stealing nesting sites needed by native species. They can also kill native animals, compete with and prey upon native predators, many of which are already struggling for survival due to other threats. Extensive rooting by feral pigs damages wetland areas, grasslands and oak woodlands, impacting roads and trails, increasing erosion, fouling water sources, and spreading disease. Bullfrogs quickly increase in wetlands and eat native amphibians as well as compete with them for food, and planted sport fish create similar impacts in streams and lakes. Exploding populations of exotic shellfish such as quagga and zebra mussels use habitat resources but do not provide food for native species. Control efforts include fencing, trapping/capture and removal, and various experimental methods in aquatic ecosystems, however the best method of control is prevention.
Management of non-native species in our parks consumes time, effort, and limited funds, and our park visitors can play an important part in controlling these invaders by not bringing non-native plants or animals to parks to release (or escape), by not transporting or disposing of non-native plants n parks, by not planting invasive plants where they might spread into parks, and by joining groups that volunteer to remove non-natives from parks and other wildlands.