Using Citizen Science Observations to Develop Managed Area Watch Lists

Invasive species are a major threat to natural ecosystems. To combat the destructive potential of arriving invasive species, many natural resource managers have adopted an "early detection and rapid response" (EDRR) strategy. A key component of EDRR is a "watch list" of invasive species that have yet to be detected in a managed area and are prioritized for surveillance, reporting, and other responses. However, managed areas with limited resources may not have the capacity to develop useful watch lists. To address this need, we developed an automated process to use data from iNaturalist, a popular citizen science platform, and a United States national list of nonnative plant species to compile a provisional watch list of the 100 most frequently reported nonnative species within a 160 km buffer around a managed area. We demonstrated the application of the process using 36 US National Park Service units with relatively small operating budgets. Using Fort Vancouver National Historic Site, Washington, as an example, we show how provisional watch lists can be refined by removing species that are unlikely to occur in the unit due to the absence of suitable habitat and prioritizing species from the state priority invasive plant list. The automated process has the advantage of being easily repeatable at regular intervals to alert managers of newly arrived species. Managers can readily modify this method for use anywhere if they have access to observation data from a citizen science platform and a list of nonnative species in the area of interest.