Exotic pest plants can have many negative impacts on native ecosystems, by disturbing a community's natural equilibrium that has evolved over hundreds of thousands of years. They displace native flora and fauna by competition for and often monopolization of resources (water, light, nutrients, and space). Some plants, such as eucalyptus and iceplant, even use allelopathy, or chemical defenses, to inhibit growth of other plant species. Invasive plants can severely alter sensitive habitats like marshes or riparian areas, affecting critical watershed health. Some invasive plant species may cause harm to native fauna. For example, European beachgrass reduces and degrades western snowy plover habitat; iceplant outcompetes native dune plants that feed the Myrtle's silverspot butterfly; and cape-ivy can be toxic to native fish.
Population Action International and Conservation International have determined that the California Floristic Province (CFP) is a "global biodiversity hotspot"--one of only 25 terrestrial regions worldwide where biological diversity is most concentrated and the threat of loss most severe (Cincotta and Engleman 2000; Conservation International 2007). Forty percent of California's grass species are exotic; today it is rare to find a pristine native California coastal prairie community, and the dominance of exotic grasses over native bunch grass species could increase with global warming (Sandel and Dangremond 2012). This is only one example of how exotic pest plants can alter the structure, function, and composition of native communities, and degrade the overall health of natural ecosystems. Within the CFP, Population Action International found that original flora covers only 25% of the landscape, with only 9.7% of this land protected in parks, reserves, refuges, and other areas off-limits to development and resource exploitation. Point Reyes National Seashore supports 49 special status rare plant species (and manages others found on the northern lands of Golden Gate National Recreation Area), many of which are directly affected by invasive non-native species. While National Park status has protected the native flora at Point Reyes from development, only active restoration will protect the native flora from invasive species.
Diversity is the spice of life
Continue reading: Choosing our Battles
Last updated: February 28, 2015