Of the over 900 species of plants in Point Reyes National Seashore, approximately 300 are non-native. Of those, at least 30 are invasive enough to threaten the diversity of native plant communities in the Seashore. The Seashore also supports 46 special status (rare) plant species, many of which are directly affected by invasive non-native species. Invasive species are second only to habitat destruction as the major cause of extinction. Population Action International and The Nature Conservancy have determined that the California Floristic Province (CFP) is a "global biodiversity hotspot" - one of 25 terrestrial regions of the world where biological diversity is most concentrated and the threat of loss most severe. Within the CFP, original extent of flora remaining is only 25%, with only 9.7% protected. National Seashore status has protected our flora from development, but not from invasive species.
Invasive species are transported both intentionally (as food, ornamentals, etc.) and unintentionally (seeds or plant fragments in feed, bedding or gravel, etc.) by humans in our highly mobile global society. An invasive species is one that displays rapid growth and spread, allowing it to establish over large areas. Free from the vast and complex array of natural controls present in their native lands, including herbivores, parasites, and diseases, exotic plants may experience rapid and unrestricted growth in new environments. Invasiveness is enhanced by features such as strong vegetative growth, abundant seed production, high seed germination rate, long-lived seeds, and rapid maturation to a sexually reproductive (seed-producing) stage. Invasive plants reproduce rapidly, either vegetatively or by seed. Their phenomenal growth allows them to overwhelm and displace existing vegetation and form dense one- to few-species stands.
With so many non-native species to manage, Seashore vegetation managers must prioritize removal efforts to maximize effectiveness. Priorities are set with the goal of minimizing the total long-term workload. Therefore, we act to prevent new infestations and assign the highest priority to existing infestations that are the fastest growing, most disruptive and affect the most highly valued (in terms of intact and/or rare plant communities) of the Seashore.
High-priority species include giant plumeless, yellow star, purple star, and distaff thistle, cape ivy, pampas grass, French and Scotch broom, European dune grass and iceplant. Mapping the extent of infestations is critical to prioritization. Several invasive species are too widespread for total control to be feasible. In these cases, priority for control is given to high-value areas, such as the Abbotts Lagoon area where rare dune plants and plant communities still maintain a fragile foothold.
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