The United States regulates deliberate species introduction by blacklists: any species not blacklisted may be imported. Half of invasive introduced species were deliberately introduced, yet most were not blacklisted, so this system is not working. White lists are also needed: no species can be deliberately introduced unless experts place it on a white list. The United States has not closed pathways for inadvertent introductions, which are regulated by international treaties. Risk assessments for introduced species have mostly targeted species as potential vectors for pathogens rather than as potentially invasive themselves. Although multilateral treaties mandate quantitative risk assessments for exclusions of species or goods that may carry them, biologists and economists can predict probabilities of invasiveness, and associated costs, only with enormous confidence limits. However, assessing risk can lead to insights on the likelihood of impact. The crucial decision will be to what extent the precautionary principle will be implemented. An added problem is that species established in parts of the United States (either native or introduced) have become invasive when introduced elsewhere in the United States. There is scant legal basis for preventing such introductions. To stem the flood of invasive species into and within the United States would require blacklists, a white listing procedure, and tighter regulation of pathways.

This paper reviews recent work examining two topics of economic research vital for invasive species policy—integration and valuation. Integration requires bioeconomic models that blend invasive biology with economic circumstances and the feedback loops between the two systems. Valuation requires nonmarket valuation associated with human and environmental damages posed by invasive species. We argue for a second-level of integration in invasive species economics—valuation based on integration models. Policy prescriptions based on integration models need valuation work; valuation surveys need integration models—the two are complements. Valuation could be enhanced with integration in mind; integration could be made better with valuation in mind. An example from blending the two research areas is presented and its merits demonstrated.

The prevention of invasive species is modeled as a “weaker link” public good. Under the weaker link aggregation technology, individual contributions beyond the lowest level will provide benefits, but these benefits progressively decline as contributions exceed the minimum. A two-region model is constructed, assuming incomplete information concerning costs of provision. This framework allows us to explain why we observe underinvestment in prevention, how information facilitates efficiency, and under what conditions information is most relevant. Specific implications regarding improved invasive species prevention policy are extracted and discussed.

We present a conceptual, but empirically applicable, model for determining the optimal allocation of resources between exclusion and control activities for managing an invasive species with an uncertain discovery time. This model is used to investigate how to allocate limited resources between activities before and after the first discovery of an invasive species and the effects of the characteristics of an invasive species on limited resource allocation. The optimality conditions show that it is economically efficient to spend a larger share of outlays for exclusion activities before, rather than after, a species is first discovered, up to a threshold point. We also find that, after discovery, more exclusionary measures and fewer control measures are optimal, when the pest population is less than a threshold. As the pest population increases beyond this threshold, the exclusionary measures are no longer optimal. Finally, a comparative dynamic analysis indicates that the efficient level of total expenditures on preventive and control measures decreases with the level of the invasive species stock and increases with the intrinsic population growth rate, the rate of additional discoveries avoided, and the maximum possible pest population.

Prioritizing exotic or invasive pest threats in terms of agricultural, environmental, or human health damages is an important resource allocation issue for programs charged with preventing or responding to the entry of such organisms. Under extreme uncertainty, program managers may decide to research the severity of threats, develop prevention or control actions, and estimate cost-effectiveness in order to provide better information and more options when making decisions to choose strategies for specific pests. We examine decision rules based on the minimax and relative cost criteria in order to express a cautious approach for decisions regarding severe, irreversible consequences, discuss the strengths and weaknesses of these rules, examine the roles of simple rules and sophisticated analyses in decision making, and apply a simple rule to develop a list of priority plant pests.

Pest-free status certification is desirable if the demand-side impacts (increased export revenue) and supply-side impacts (lower pest damage and decreased ongoing control costs) exceed the compliance monitoring and eradication costs. Thus, eradication may be optimal without certification. Certification is more likely for regions facing costly treatment requirements (bans) or possessing geographic traits that lower monitoring costs and infestation probabilities than for those exporting higher-valued products. Certification benefits producers but hurts consumers. Thus, political feasibility may be greater if domestic consumption is a small share of the market and if the additional tax burden of certification programs is light.

Invasive species change ecosystems and the economic services such ecosystems provide. Optimal policy will minimize the expected damages and costs of prevention and control. We seek to explain policy outcomes as a function of biological and economic factors, using the case of Hawaii to illustrate. First, we consider an existing invader, Miconia calvescens, a plant with the potential to reduce biodiversity, soil cover, and water availability. We then examine an imminent threat, the potential arrival of the Brown treesnake (Boiga irregularis). The arrival of the snake in Guam has led to native bird extirpations, power outages, and health costs.

This paper presents a bioeconomic model of a commercial fishery facing biological invasion by an alien species acting as a space competitor for the native species. The model is illustrated in a case study of the common scallop fishery of the Bay of St-Brieuc (France), where biological invasion by a slipper-limpet (Crepidula fornicata) is now addressed by a control program. First we present the model, which combines the dynamics of the two competing stocks. We then use the model to analyze the equilibrium of the fishery under various assumptions concerning invasive species control, and to assess the social cost of the invasion. Finally we propose a set of dynamic simulations concerning the ongoing program, emphasizing the influence of its starting date on its overall economic results.

A conceptual bioeconomic framework that integrates dynamic epidemiological-economic processes was designed to analyze the effects of invasive species introduction on decision making in a livestock sector (e.g., production and feeding). The framework integrates an epidemiological model, a dynamic livestock production model, domestic consumption, and international trade. The integrated approach captures producer and consumer responses and welfare outcomes of livestock disease outbreaks, as well as alternative invasive species management policies. Scenarios of foot-and-mouth disease are simulated to demonstrate the usefulness of the framework in facilitating invasive species policy design.

Asian soybean rust (rust) is an emerging issue in U.S. crop production and was identified in nine states during 2004. Recent farm surveys indicate that many producers are adjusting their management practices to the possibility of a rust infestation. The economic and environmental impacts of such adjustments are not known in the medium run given these new developments. We combine 2005 data on the geographical distribution of the fungal pathogen that causes rust with 2005 information on the availability and material costs of fungicides to analyze three treatment strategies. Our results indicate a higher range of economic impacts than previous research has indicated, but are consistent with earlier findings indicating that rust infestations will likely result in reduced soybean production, reduced exports, and higher prices.

Asian gypsy and nun moth introductions into the United States, possibly arriving on imported Siberian coniferous logs, threaten domestic forests and product markets and could have global market consequences. We simulate, using the Global Forest Products Model (a spatial equilibrium model of the world forest sector), the consequences under current policies of a widespread, successful pest invasion, and of plausible trading partner responses to the successful invasion. We find that trade liberalization would have a negligible effect on U.S. imports of Siberian logs and, consequently, on the risk of a pest invasion. But, if it happened, possibly through trade in other commodities, a successful and widespread pest invasion would have large effects on producers and consumers over the period 2002 to 2030.

This paper presents a dynamic principal-agent model of aquatic species invasions in which a manager, concerned about the spread of invasive species across lakes by boaters, sets interseasonal management controls on a lake-by-lake basis, and boaters make a series of intraseasonal trip decisions to maximize random utility during the course of the season, conditional on the controls imposed by the manager. The results of a simulated invasion of Eurasian watermilfoil (Myriophyllum spicatum) highlight interesting aspects of the optimal management policies under two different management objectives: maximizing boater welfare and minimizing milfoil spread.

This paper presents a case study of the economic damages to homeowners in a northern New Jersey community due to an exotic forest insect—the hemlock woolly adelgid. Hedonic property value methods are used to estimate the effect of hemlock health on property values. A statistically significant relationship between hemlock health and residential property values is established. Moreover, there are some signs of spillover impacts from hemlock decline, as negative effects are realized on the parcels where the declining hemlock stands are located as well as on neighboring properties. These results give some indication of the benefits of potential control programs and strategies and also show support for community- or neighborhood-based programs in residential settings.

Plant invasions and their impact on land use pose difficult research questions, due to the complex relationships between the ecological nature of the invasion and the human responses to the invasion. This paper focuses on the linkages between an invasion of bracken fern and land use decisions in an agricultural frontier in southern Mexico. Agriculture in this region is practiced on an extensive basis, using traditional slash-and-burn techniques of temporary cultivation and continuous rotation through forest fallow. We investigate the factors that affect the decision of a subsistence farmer to either continue cultivating an invaded agricultural plot or permanently abandon the plot and cultivate elsewhere. We develop an agricultural household model of land use choices, where households maximize utility subject to constraints on land, labor, and income. We subsequently test the hypotheses raised, using data from a small household survey performed in the region in 2002.

This paper reviews the literature on the economics of invasive species management as it applies to invasive species in general and terrestrial invasive species in particular. The paper summarizes a number of recent studies that assign values to the economic impact of terrestrial invasive species on a national scale. This is followed by a review of the economic literature on control and prevention of a biological invasion and the literature on international trade and trade policy with invasive species. The paper then reviews selected studies on terrestrial invasive plants, animals, and microbes, respectively.

Invasive species are a growing threat in the United States, causing losses in biodiversity, changes in ecosystems, and impacts on economic enterprises such as agriculture, fisheries, and international trade. The costs of preventing and controlling invasive species are not well understood or documented, but estimates indicate that the costs are quite high. The costs of aquatic invasive species are even less well understood than those for terrestrial species. A systematic approach is needed to develop a consistent method to estimate the national costs of aquatic invasives. This review of the economic literature on aquatic invasive species is the first stage in the development of that estimate. We reviewed over sixty sources and include both empirical papers that present cost estimates as well as theoretical papers on preventing and mitigating the impacts of aquatic invasive species. Species-specific estimates are included for both animals and plants.