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The goal of the Invasive Plant Management program is to provide a comprehensive framework to protect the park’s natural and cultural resources from the impacts of non-native invasive plants. Yosemite resource managers use Integrated Pest Management (IPM), a sustainable approach to managing pests, by combining the best available science and tools in a way that minimizes risk, whether human health, environmental, or economic. Elements of IPM include prevention, inventory/early detection, prioritization, treatment, monitoring, and education and outreach. Managers implement IPM through adaptive management which promotes flexible decision making to allow for program adjustments in the face of uncertainties and with an aim to reduce uncertainty over time via monitoring. This process allows resource objectives to be met while information is gathered and lessons are learned, in hopes of continually improving future management.
Prevention measures also include working with contractors on two separate prevention programs: equipment inspection [63 Kb PDF], and pre-procurement gravel-pit inspection [190 kb PDF]. All heavy equipment entering the park is inspected to make sure weed seed harboring soil is cleaned from the machine before it arrives at the park. All gravel, fill, topsoil, and other construction materials are sourced from within the park or from inspected gravel pits to reduce the introduction and spread of infestations. An additional preventative measure is the cooperation between Yosemite National Park and the park concessioner to use certified weed-free forage to feed stock.
Catching infestations early enables managers to respond while populations are still small and easy to manage. This is critically important because the probability of eradication is much greater when invasive plant populations are small. The management response, therefore, requires far fewer personnel, equipment, and monetary resources, and would potentially use tools that are less intrusive to the surrounding landscape. In the figure below, one can see how dramatically the cost of control increases with increasing infestation size while the chance of success declines.
In order to successfully manage invasive plants in Yosemite, it is important that we are aware of what we have, including the presence and absence of target species. All survey efforts are tracked even when no target species are found in order to improve the reliability of the mapping effort, and to improve our understanding of the likelihood of habitats to become invaded. This data provides for the prioritization and planning of treatments and the ability to assess the success of management actions. Because it is not practical to inventory each of the 761,266 acres within Yosemite National Park, inventories focus on areas most likely to be invaded, but include enough other sampling areas to inform managers about where invasive species occur or do not occur. High probability areas include both natural and manmade disturbance sites, particularly those exposed to a ready source of invasive plants propagules.
Identifying pathways for invasive species entry and spread can help managers make informed management decisions regarding park prevention systems and early detection efforts. Maintaining an invasive species inventory is an ongoing process. Sophisticated mapping technology allows managers to inventory and document areas of concern and catalog how infestations respond to treatment over time. Unfortunately, Yosemite National Park has no dedicated funding for early detection survey work at the present time, hence, survey work as well as treatment work has to be carefully prioritized.
The first comprehensive park-wide early detection survey was conducted between 2012 and 2014, funded by the Yosemite Conservancy. The goal of this project is to provide park resource managers with a comprehensive inventory of non-native plants and baseline data on their distribution throughout the park. Upon completion of the project, 30 new non-native plants have been discovered within the boundaries of Yosemite, including highly aggressive weeds such as Medusahead (Elymus caput-medusae) and rush skeleton weed (Chondrilla juncea). Additionally, isolated patches of high priority invasive plants such as velvet grass and cheat grass have been found in remote wilderness locations. View a poster showcasing the results of this project. [9.9 MB PDF]
Another early detection effort in Yosemite is the Burned Area Rehabilitation (BAR) program. After major fires, Yosemite botanists conduct early detection surveys and enact rapid response treatments in all areas disturbed by firefighting operations that may be susceptible to new invasive species introductions.
By finding these threats before they become established, park staff are able to control the infestations with minimal time and resources. Early detection efforts such as these protect valuable natural resources and have the potential to save thousands of dollars in the future.
With the prioritization of Yosemite's invasive plant inventory, staff are able to implement the most appropriate control technique (i.e. manual control, mechanical control, herbicides) for each individual threat. Control operations can vary greatly from species to species depending on environmental factors and specific plant characteristics. Invasive plant control efforts are monitored in order to determine the efficacy of treatment methods and need for additional control measures. Learn more about Yosemite's control techniques.
The elements of monitoring allow for an adaptive approach so that park managers can adjust control methods as necessary to improve treatment success in the future. Monitoring is a crucial step in an iterative process that can benefit land managers in other parts of the Sierra Nevada and elsewhere. Land managers from other regions can learn from treatment successes and failures documented in Yosemite, thus, informing and assisting with their management decisions. Additionally, this information can be synthesized in ways that incorporate diverse methods of outreach and education to reach a greater audience.
Research, Education, and Outreach
Diverse education and outreach efforts can foster understanding of invasive plant prevention and control to a wide range of audiences. One method includes educating, training, and using volunteers, who are an essential component of invasive plant management in the park. Volunteering allows members of the public to forge a deeper relationship with the park, and become stakeholders in park resource challenges. Many volunteers return year after year to work on projects that they have become connected with. Volunteers are the frontline defense against invasive plants like bull thistle (Cirsium vulgare) in Yosemite Valley meadows and the Mariposa Grove. Additionally, restoration projects throughout the park that help foster ecosystems resilience to invasion rely heavily on volunteers. Yosemite would not be able to achieve the many resource management goals set forth without the support of dedicated volunteers. Learn more about how to become a volunteer.
Yosemite posts the Invasive Plant Management annual work plan [2.3 MB PDF] on the park's website, as well as in newspapers, journals, conferences, brochures, and visitor center exhibits. This strategy allows the park to communicate invasive plant research and other relevant information to park staff, partners, and visitors. Other outreach materials are created periodically to keep the public well informed about current and ongoing projects. For example, information about velvetgrass [1.1 MB PDF], blackberry treatment [1.6 MB PDF], and the Ahead of the Spread [9.9 MB PDF] project, can be expressed through informative posters.
You can do your part to help keep Yosemite beautiful. Work alongside park biologists to remove invasive plants throughout the park. Many group work projects, which include invasive species removal as well as other natural resources projects, can be scheduled in advance through the volunteer office. Call 209/379-1308 to register. Learn more about volunteering in Yosemite.
Map Invasive Plants Using Your Smart Phone with CalFlora Observer Pro
Did you know that you can help fight weeds in Yosemite National Park with your smart phone? Yosemite teamed up with CalFlora, The Yosemite Conservancy, and other land management agencies to develop an easy to use smart phone app that allows you to contribute valuable data to your park. If you encounter invasive plants during your visit, use this app to simply Download the app for Android or Apple devices.
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If interested in learning more, download Yosemite's overall Integrated Pest Management Plan [8 MB PDF], which includes some information about invasive plants.
Last updated: April 24, 2019