A plant that has been introduced (either intentionally or not) to a new geographical area is non-native, but not necessarily invasive. Invasive plant species display particular characteristics like fast growth, high seed production, and rapid maturation that—when combined with a lack of the natural predators and diseases that help control them in their native environment—allow them to rapidly grow and spread, overwhelming and displacing native vegetation. National parks in the San Francisco Bay Area are crucial natural refuges in a largely developed area. Invasive plants threaten these sanctuaries by permeating the landscape, altering ecosystem processes, and deteriorating habitat for many native plants and animals, including rare, threatened, and endangered species.
Being near developed areas also means that the parks are subject to a continuous barrage of non-native and invasive species growing nearby. Managing this constant stream of invaders is a daunting task. The NPS SFAN Early Detection Program focuses on identifying, mapping, and eradicating the most invasive plant species before they become wide-spread. To accomplish their goals they also rely heavily on the volunteer-based Weed Watchers program as well as numerous partnerships with other invasive plant management teams and the Bay Area Early Detection Network (BAEDN). Since early detection began in 2008, NPS staff, interns and Weed Watcher volunteers have mapped more than 5,000 priority invasive plant populations over more than 1,000 miles of roads and trails.