Mark E. Eiswerth

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 invaders 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 stocks intrinsic rate of growth, the carrying capacity afforded the invasive species, and the form of the invaders 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.

The value of water levels in water‐based recreation: A pooled revealed preference/contingent behavior model

In this paper we present estimated recreation values for preventing a decline in water levels at, and even the total loss of, a large western lake that is drying up. We use a Poisson version of the count data travel cost model; however, in addition to and in combination with revealed preference (RP) data, we employ contingent behavior (CB) responses to hypothetical questions on alternative water levels and number of trips. The pooled model used allows for tests of differences between results using RP and CB data. This particular pooled RP/CB approach has not to our knowledge previously been applied to examine the values of alternative water quantities in water-based recreation.

Prevention or Control: Optimal Government Policies for Invasive Species Management

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.

Potential Environmental Impacts and Economic Damages of Eurasian Watermilfoil (Myriophyllum spicatum) in Western Nevada and Northeastern California1

Abstract: Eurasian watermilfoil, an aquatic invasive weed, has been identified recently at a number of sites in western Nevada and northeastern California, including Lake Tahoe. Because Eurasian watermilfoil is easily spread by fragments, transport on boats and boating equipment plays a key role in contaminating new water bodies. This is an important means of the potential spread of this weed throughout key recreational and agricultural areas surrounding Lake Tahoe. Unless the weed is controlled, significant alterations of aquatic ecosystems, with associated degradation of natural resources and economic damages to human uses of those resources, may occur. This research uses the economic valuation approach known as benefits transfer to estimate the value of a portion of the recreational service flows that society currently enjoys in the Truckee River watershed below Lake Tahoe. The lower-bound estimates of baseline water-based recreation value at a subset of sites in the watershed range from

Maximizing conserved biodiversity: why ecosystem indicators and thresholds matter

30 to

Input–output modeling, outdoor recreation, and the economic impacts of weeds

45 million/yr. Impacts from the continued spread of Eurasian watermilfoil in the watershed could be significant; for example, even a 1% decrease in recreation values would correspond to roughly

Adjusting benefits transfer values for inflation

500,000/yr as a lower bound. Nomenclature: Eurasian watermilfoil, Myriophyllum spicatum L. #3 MYPSP. Additional index words: Aquatic weeds, economic impacts, invasive species, recreation, MYPSP.

Dynamic Benefit-Cost Analysis for Controlling Perennial Pepperweed (Lepidium latifolium): A Case Study'

Abstract Accounting for biodiversity is important in several different types of constrained choice problems, including public and private decisions for habitat and species conservation, the establishment of recreational parks and natural areas, mitigation banking, and natural resource damage assessment (particularly primary and/or compensatory restoration planning and scaling). In such applications it is important to give careful consideration to (1) the choice of biodiversity indicator(s) to be used, and (2) the role of discontinuous, nonlinear ecological processes in light of the decisionmakers chosen time horizon. The former is important because the choice of indicator(s) can substantially influence decisions about conservation priority-setting and planning. The latter is critical for the same reason, notwithstanding that dynamic ecosystem processes have rarely been considered sufficiently, if at all, in such applications (in part because the processes usually are poorly understood or measured). In this manuscript we use avian diversity data, collected by one of the authors, from hardwood forest ecosystems in the eastern United States. We couple these data with estimates of species prevalence factors to construct a case study of how indicator choice and consideration of ecological thresholds influence the outcomes of biodiversity preservation problems. We show that (1) the choice of indicator(s) is critical, (2) failure to account for nonlinear, threshold effects in an ecosystems future progression alters preservation decisions and ignores important information, (3) the effect of choosing different time horizons depends on the indicator used, and (4) for any given biodiversity indicator, dynamic solutions can depend on the time horizon chosen but not necessarily in monotonic or simple fashion. Our case study highlights the importance of further system-specific research on dynamic ecological progressions as well as uncertainty regarding future supply and demand for ecosystem service flows.

Determinants of Threatened Sage Grouse in Northeastern Nevada

Abstract Nonindigenous invasive weed species can have substantial negative impacts on the quantity and quality of outdoor recreational activities such as fishing, hunting, hiking, wildlife viewing, and water-based recreation. Despite the significance of impacts on recreation, very little research has been performed to estimate the corresponding economic losses at spatial scales such as regions, states, and watersheds. This is true primarily because in most jurisdictions the data necessary to estimate recreational impacts are scarce and incomplete. Because of the challenges involved in measuring recreational losses precisely, we illustrate a method that can provide indications of the ranges in which the true economic losses likely lie. To reflect underlying uncertainty in parameters such as the number of acres infested in a jurisdiction and the rate at which wildlife-related recreation decreases as a function of increasing weed infestation, we developed a range of estimates using lower, medium, and higher scenario combinations of parameter and variable values. Our case study jurisdiction is a western state (Nevada) in which nonindigenous weed infestations on public lands have expanded rapidly in recent years. Under conservative assumptions, the negative economic impacts stemming from the adverse influence of nonindigenous weeds on wildlife-related recreation in Nevada likely range from

The Child Adoption Marketplace: Parental Preferences and Adoption Outcomes

6 million to