A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 23 – non-native plants

Tu, Mandy; Demetry, Athena; Saah, David

Non-native (exotic, introduced, alien) species are non-indigenous species, such as plants, animals, and microbes, which have been introduced to new areas beyond their native ranges, and refer only to their place of origin. In contrast, invasive species are a subset of those non-native species that once introduced, are able to colonize and spread beyond cultivation and human care to impact natural habitats, biological diversity and/or the economy (Schwartz et al. 1996, Wilcove 1998, Pimental et al. 2005, NISC 2006). Non-native invasive species are widely recognized as posing threats to biological diversity second only to direct habitat loss and fragmentation, and have been implicated in the decline of endangered species worldwide (Baillie et al. 2004). Non-native invasive plants in particular are known to outcompete or displace native plants, provide unsuitable forage or nesting sites for native wildlife species, alter gene pools through hybridization, or alter vital ecosystem processes such as fire, hydrology and nutrient cycling (Macdonald et al. 1989, D’Antonio & Vitousek 1992, Chornesky & Randall 2003). In the United States, thousands of non-native plant species have been intentionally or accidently introduced for a multitude of reasons, such as for food, ornamental use, erosion control and other reclamation purposes, and many species have also arrived as hitchhikers in agricultural products, ship ballast, or transported on road machinery (Kolar & Lodge 2000, Mack 2003, Ruiz & Carlton 2003). Of these thousands of non-native plants however, it is estimated that less than 4% have the tendency to escape cultivation and become invasive in natural areas (Rapaport 1991), severely impacting native biological diversity and habitat functions. In California, approximately 18% of the plant species found in the wild are non-native in origin, with the majority of exotic species establishing in the past 150 years (Randall et al. 1998). The California Invasive Plant Council (Cal-IPC) maintains a list of Exotic Pest Plants of Greatest Ecological Concern in California that includes only invasive pest plants of natural areas (Cal-IPC 2006, 2007). This current inventory contains a total of 198 species (ranked as 39 High, 93 Moderate, and 67 Limited), indicating that only a relatively small proportion of those non-native species cause significant ecological damage. The National Park Service (NPS) acknowledges the spread of invasive species as one of the major factors contributing to ecosystem change and instability. Across the NPS, 6,500 non-native invasive species have been documented on park lands, 70% of documented invasive species on park lands are invasive plant species, and around 5% of park lands are dominated by invasive plants (NPS 2009). Sequoia-Kings Canyon National Parks (SEKI) has recognized the threat of non-native invasive plants to its resources and values for some time (NPS 1999, NPS 2006a) and in 2001 started an active management program to map, monitor and control their invasive plants (Demetry 2010). Additionally, since 2002, a parkwide weed database works to track the current status of mapped invasive plant populations and management progress. This database was initially populated by data from a 1996-1998 weed survey, and now also contains recently mapped weeds, but does not include other past plant datasets.

A natural resource condition assessment for Sequoia and Kings Canyon National Parks: Appendix 23 – non-native plants

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