Practical Considerations for Early Detection Monitoring of Plant Invasions

Abstract

Invasions by multiple nonnative species into wildland areas require that decisions be made on which species and sites to target for early detection monitoring efforts and ultimately management actions. Efficient allocation of resources to detect invasions from outside of a management unit, and to monitor their spread within a management unit, leaves more resources available for control efforts and other management priorities. In this chapter, we describe three types of monitoring plans that are possible given three typical scenarios of data availability within or adjacent to the management unit: (1) there are no data on invasive species, (2) there are species lists of invasives, and (3) there are georeferenced abundance data for invasive species. In the absence of invasive species data, monitoring must be guided based on the general principals of invasion biology related to propagule pressure and plant resource availability. With invasive species lists, prioritization processes can be applied to narrow the monitoring area. It is also helpful to develop separate prioritized lists for species that are currently colonizing, established but not spreading, and those that have begun to spread within a management unit, because management strategies differ for species at different phases of the invasion process. With georeferenced abundance data, predictive models can be developed for high priority species to further increase the efficiency of early detection monitoring. For the majority of invasive species management programs, we recommend a design based on integrating prioritization and predictive modeling into an optimized monitoring plan, but only if the required species information and resources to process them are available and the decision is based on well-defined management goals. Although the up-front costs of this approach appear to be high, its long-term benefits can ultimately make it more cost-effective than less systematic approaches that typify most early detection programs.