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Ecology and Management of Invasive Species
Dean Pearson, USDA Forest Service, Rocky Mountain Research Station, Missoula, MT
Biological invasions present unique natural resource management challenges. When exotic species invade native systems, they shift the system out of its natural equilibrium dynamic and launch it onto a new trajectory defined by the invader’s impacts – the invasion trajectory. Understanding biological invasions in light of the invasion trajectory is crucial to effective invasive species management. Although management practices such as chemical and biological control offer powerful tools that can alter the invasion trajectory, they rarely extirpate the invasive species and return the system to its historic state. Moreover, much like in human medicine, management tools can have potentially negative side effects that can exacerbate the problem. Thus, effective invasive species management requires understanding the invasion trajectory and how management tools alter the trajectory so we can ensure that management actions improve system conditions. Here, we present a heuristic model for understanding, studying, and managing biological invasions in this light. We provide examples from an ongoing research program on spotted knapweed to illustrate the importance of determining the invasion trajectory in order to predict the community-level impacts of the invader over time and provide a baseline for evaluating the efficacy of management actions. We discuss how applying this approach can provide managers with the necessary knowledge to make informed decisions that will maximize efficacy and minimize side effects of management actions.