Managing nonindigenous invasive species: Insights from dynamic analysis

Accidental introductions of nonindigenous invasive species impair ecosystems, increase the risk of native species extinctions, and cause substantial economic damages on a worldwide basis. Despite the magnitude of the problem, very little economic analysis has been focused on this topic to date. This manuscript develops an optimal control model of the management of a nonindigenous species stock following its introduction and establishment. We find that the influence of changes in ecological and human factors (such as the invader's intrinsic growth rate, carrying capacity, and the effectiveness of invasive species management technologies) on the optimal level of management are analytically (mathematically) ambiguous in sign and depend on the values of other parameters and variables. To estimate actual numerical solutions to the model and conduct sensitivity analyses, we construct a case study illustration based on invasive plant species on arid lands. The illustration shows that the optimal level of management effort is sensitive to biological and ecological factors (the stock's intrinsic rate of growth, the carrying capacity afforded the invasive species, and the form of the invader's growth function) that are species- and site-specific as well as uncertain given currently available scientific information. This highlights the need for better collaboration and information transfer between economists and scientists interested in this topic. Given that resources for addressing nonindigenous species threats typically are quite constrained, and complete eradication in a particular area is often technically infeasible, the model provides useful insight on optimal levels of ongoing management and how they may vary according to bioeconomic factors.