Importing exotic plants and the risk of invasion: are market-based instruments adequate?

Exotic plant species are often intentionally imported into regions outside of their normal range as ornamental plants or as breeding stock, thereby generating benefits for consumers and producers. However, one of the unintended side effects of such introductions is that the exotic plant species may become invasive. Prohibiting sale of this type of exotic plant species, on the basis that it may become invasive, will have social costs in the form of foregone consumer benefits and nursery profits. We develop a model of a private commercial plant breeding industry that imports an exotic plant species into a region. The risk associated with invasion is modeled using a probabilistic ‘hazard function’, the key determinants of which are the characteristics of the exotic plant and the number of commercial nurseries contributing to its dispersal. We consider the possibility of employing market-based instruments (e.g., Pigovian tax) consistent with the concept of ‘introducers pay’, to regulate the nursery industry. We then provide an empirical illustration using the historical introduction of saltcedar (Tamarisk spp.) into the United States. Our results indicate that the mere presence of a risk of invasion does not mean that it is socially optimal to prevent commercial sales of an exotic plant species. Indeed, there appear to be plausible forms of the functional relationships involved that require only a modest reduction in the private industry optimum. In contrast, no sales of the exotic plant should occur at all under several sets of assumptions about the level of invasion risk and the linkage between dispersal sites and invasion hazard.     

Using an integrated fuzzy set and deliberative multi-criteria evaluation approach to facilitate decision-making in invasive species management

There are two issues at the core of invasive species risk management: on the one hand, decision-makers struggle to balance environmental goals against other often competing societal goals such as economic benefits and social welfare; on the other hand, uncertainty often prevails in understanding the invasion process and in communicating invasion risks to the stakeholders. In this paper, we describe how an integrated Deliberative Multi-Criteria Evaluation (DMCE) and fuzzy set approach can tackle these two issues in the analysis of alternative risk management strategies, using the example of European House Borer (EHB, Hylotrupes bajulus Linnaeus). DMCE offers a platform for stakeholders to interact and to make a trade-off decision between multiple goals based on social learning and deliberation. The fuzzy set approach, applied within a DMCE framework, explicitly incorporates the inherent uncertainty in estimating potential EHB impacts and in evaluating participants' subjective preferences. This integrated method, therefore, provides a promising approach for tackling the dual challenges of competing goals and uncertainty in the evaluation of invasive species risk management options.     

Spatial economic analysis of early detection and rapid response strategies for an invasive species

Economic impacts from invasive species, conveyed as expected damages to assets from invasion and expected costs of successful prevention and/or removal, may vary significantly across spatially differentiated landscapes. We develop a spatial–dynamic model for optimal early detection and rapid response (EDRR) policies, commonly exploited in the management of potential invaders around the world, and apply it to the case of the Brown treesnake (Boiga irregularis) in Oahu, Hawaii. EDRR consists of search activities beyond the ports of entry, where search (and potentially removal) efforts are targeted toward areas where credible evidence suggests the presence of an invader. EDRR costs are a spatially dependent variable related to the ease or difficulty of searching an area, while damages are assumed to be a population-dependent variable. A myopic strategy in which search only occurs when and where current expected net returns are positive is attractive to managers, and, we find, significantly lowers present value losses (by $270 m over 30 years). We find further that in the tradeoff between search costs and damages avoided, early and aggressive measures that search some high priority areas beyond points of entry even when current costs of search exceed current damages can save the island more ($295 m over 30 years). Extensive or non-targeted search is not advised however.     

A bioeconomic model for determining the optimal response strategies for a new weed incursion

Invasions by non-indigenous plant species pose serious economic threats to Australian agricultural industries. When a new invader is identified a rapid response is critical, particularly if the invasive species has the ability to spread rapidly. An early decision is required whether to attempt to eradicate or contain the infestation, or do nothing and leave it to landholders to manage. These decisions should be based on economic considerations that account for long term benefits and costs. This paper describes a bioeconomic simulation framework with a mathematical model representing weed spread linked to a dynamic programming model to provide a means of determining the economically optimal weed management strategies over time, from the government’s perspective. The modelling framework is used to evaluate hypothetical case study invasive weed control scenarios in the Australian cropping systems. The benefit–cost ratios of invasion control are shown to be generally very high and clearly, there are significant benefits to be achieved by controlling highly invasive weeds when initial infestations are at a low level. Even if the invasion cannot be eradicated due to its high invasiveness or budget constraints, it still pays to maintain invasions at low levels.     

The Asian clam Corbicula fluminea in the European freshwater-dependent industry: A latent threat or a friendly enemy?

While the biofouler Corbicula fluminea (Müller, 1774) is known to cause great economic losses in North America, studies reporting the problem in Europe are much scarcer. This paper explores the industrial effects of the species in Portugal, the gateway by which the bivalve entered Europe around 30 years ago. National waterworks, major power stations, cement plants, pulp and paper mills and irrigation systems were surveyed. The industrial impacts of the pest were shown to remain relatively mild; irrigation systems are those that seem to be facing more significant economic losses due to infestation. Possible reasons for the apparent discrepancy between this result and the species dispersal in natural ecosystems are discussed, and recommendations on adequate responses to the latent threat are provided. This study may assist the implementation of integrated pest management policies in countries at risk of invasion or recently invaded, and contribute to an understanding of the species’ progression in industrial environments.     

The welfare impacts of an invasive species: Endogenous vs. exogenous price models

The “fixed-prices” models used to measure damages from invasive species typically overestimate financial impacts. These fixed-price assessments do not address key behavioral modifications that lower costs as people adapt by changing their mix of inputs and outputs given new economic circumstances. Using the invasive emerald ash borer (Agrilus planipennis) in Ohio as a motivating example, we develop a computable general equilibrium model that accounts for these behavioral responses. We estimate annual damages from the beetle to be about $70 million, an order of magnitude less than the $400–$900 million in damages estimated using a fixed-price model. Damages are lower because people adapt through price and income adjustments that occur after ash trees are devastated from the emerald ash borer.     

Reassessing the costs of biological invasion: Mnemiopsis leidyi in the Black sea

Invasions of ecosystems by exotic species have been the focus of a growing body of research in applied biology and ecology, but relatively little attention has been paid to their economic consequences. Even where economic estimates have been made these often make ad hoc assumptions about the biological relationships of interest and lack grounding in economic theory. This paper develops an integrated ecological-economic approach to assess the economic consequences of invasion for a commercially harvested endemic species whose population dynamics are altered by the invader. As a case study, the Black Sea anchovy fishery represents an interesting example of such a situation. In the early 1980s, the comb jelly Mnemiopsis leidyi invaded the Black Sea, eventually becoming established and experiencing a population explosion with dire consequences for the commercial anchovy fishery. In modeling the population dynamics of the Black Sea anchovy (Engraulis encrasicolus), the influence of Mnemiopsis is incorporated as a structural change in the anchovy stock-recruitment relationship. Then the economic loss associated with this structural change is assessed, using a discrete, dynamic bioeconomic model. It is shown that Mnemiopsis had a dramatic effect on the potential sustainable harvest from an optimally managed anchovy fishery but these losses were at least an order of magnitude lower than estimates cited elsewhere.     

Monopoly pricing when consumers are antagonized by unexpected price increases: a “cover version” of the Heidhues–K?szegi–Rabin model

This paper reformulates and simplifies a recent model by Heidhues and K?szegi (The impact of consumer loss aversion on pricing, Mimeo, 2005), which in turn is based on a behavioral model due to K?szegi and Rabin (Q J Econ 121:1133?C1166, 2006). The model analyzes optimal pricing when consumers are loss averse in the sense that an unexpected price hike lowers their willingness to pay. The main message of the Heidhues?CK?szegi model, namely that this form of consumer loss aversion leads to rigid price responses to cost fluctuations, carries over. I demonstrate the usefulness of this ??cover version?? of the Heidhues?CK?szegi-Rabin model by obtaining new results: (1) loss aversion lowers expected prices; (2) the firm??s incentive to adopt a rigid pricing strategy is stronger when fluctuations are in demand rather than in costs.     

The bioeconomics of tritrophic systems: applications to invasive species

Adapted species in nature are assumed to have solved renewable resource management problems, and this is examined here using a physiologically based model of energy acquisition and allocation. Newly established invasive species are merely in an early phase of this process in their new environment. Analogies between the economies of humans and other species are used to develop an objective function for individual utility of energy allocation. The objective function includes the physiologically based population dynamics models of the consumer and resource species in a food chain as constraints. The model applies to all trophic levels in a food chain including human harvesting of renewable resources (see also Regev et al. (Regev, U., Gutierrez, A.P., Schreiber, S., Zilberman, D., 1998. Biological and Economic Foundation of Renewable Resource Exploitation. Ecological Economics. 26 (3), 227-242.)).Specifically, the analysis:

• (1)Attempts to combine ecological and economic theory;
• (2)Points out the importance of time frame in the two economies (evolutionary vs. market time);
• (3)Examines the effects of expected uncertainty due to environmental hazards in defining energy acquisition and allocation strategies in two invasive aphid species at the extremes of so called r- and K-strategies and the well adapted Central American cotton–cotton bollweevil system;
• (4)Evaluates the effects of changes in behavioral and physiological parameters and environmental degradation on the abundance of resource and consumer species.

     

The ghost of extinction: Preservation values and minimum viable population in wildlife models

The inclusion of a minimum viable population in bioeconomic modeling creates at least two complications that are not resolved by using a modified logistic growth function. The first complication can be dealt with by choosing a different depensational growth function. The second complication relates to the inclusion of the in situ benefits of wildlife into the analysis. Knowledge about the magnitude of the in situ benefits provides no guide for policy about conservation management. Simply knowing that people are willing to pay a large amount each year to protect a species says nothing about whether one should manage habitat to protect or enhance the species' numbers, unless the species is in imminent danger of extinction. If willingness to pay is to be a guide, it needs to be better tied to population numbers, especially the minimum viable population.     

The Willingness to Accept Value of Statistical Life Relative to the Willingness to Pay Value: Evidence and Policy Implications

Large disparities between willingness to accept (WTA) and willingness to pay (WTP) based values of statistical life are commonly encountered in empirical studies. Standard economic theory suggests that if a public good is easily substitutable there should be no marked disparity between WTA and WTP values for the good, though the disparity increases with reduced substitutability. However, psychologists have shown that people often treat gains and losses asymmetrically and tend to require a substantially larger increase in wealth to compensate for a loss than the amount they would be willing to pay for an equivalent gain. Although most transport projects may aim to improve safety, situations arise when a relaxation of an existing regulation saves resources but increases the risk of death and injuries. A survey was recently carried out in New Zealand to determine people’s willingness to pay to reduce road risks and their willingness to accept compensation for an increase in risk. This paper reports the disparity observed between the two measures and considers some of the problems posed for policymakers.     

Economic Valuation of the Threat Posed by the Establishment of the Asian Tiger Mosquito in Australia

Invasive species policy could be better informed if we understood how much people value reductions in the risks posed by these organisms. This study investigates the public’s willingness to pay (WTP) for additional measures to reduce the risk of invasion of the Australian mainland by the Asian tiger mosquito (ATM). The study contributes to the literature by applying a stated preference method to estimate the public’s WTP to reduce the risk of an ATM invasion, expressed as a change in probability. It is the first ex ante invasive species analysis to test over two discrete invasion reduction probabilities based on management effort. Further, to overcome the challenges in valuing changes in probabilities, the study presented respondents with a well-defined discrete difference in the final probability, with one scenario reducing risk from 50 to 25% and the other from 50 to 5%. We find a significant difference in the mean WTP values between these two scenarios (A$67 vs. A$90). The overall conclusion is that estimated benefits of reducing the probability of an ATM incursion outweigh the costs.     

A comparison of contingent valuation method and random utility model estimates of the value of avoiding reductions in king mackerel bag limits

This paper estimates the value of king mackerel bag limit changes with both stated and revealed preference methods. The 1997 Marine Recreational Fishery Statistical Survey allows estimation of the value of avoiding bag limit reductions with the random utility model and the contingent valuation method. Using the contingent valuation method, the willingness to pay to avoid a one fish reduction in the bag limit is $2.45 per year. Using the random utility model, the willingness to pay to avoid a one fish reduction in the bag limit is $2.24 per trip and $7.71 for a two-month time period. Considering several methodological issues, the difference in willingness to pay between the stated and revealed preference methods is in the expected direction.     

Identifying,preventing and controlling invasive plant species using their physiological traits

A model of a plant community that is biologically reasonable and easily adaptable to economic models is presented. The model includes optimization, competition, stochastic limiting resources, and identification of redundant and invasive species. Species exhibit a rich array of traits that make them suited for some set of environmental factors and not for other sets. And because environmental factors are constantly changing, species that are very successful under one set of factors become redundant under another set, implying that an ecosystem needs redundant species as insurance. Invasive species are the flip side of redundant species as they are successful, at least under some environmental conditions. Identification depends on four physiological parameters defining each plant: two respiration parameters, a parameter that gives the plant's ideal level of the stochastic limiting resource, and the specific leaf area. The parameters are terms in an expression that gives the net energy intake of an individual plant, and the plant behaves as if it optimizes this by choosing its individual biomass. Success of species is judged based on the biomass of the species in steady state. An application extends the range management literature by incorporating the model into a rangeland manager's decision problem extends the range management literature. The model allows for multiple plant species, addresses the influence of limiting resources (other than density dependence), and tracks the response of the entire system to human and natural system perturbations. The methods allow simple predictions of community composition in the face of jointly determined economic/ecological behavior. The power of the method is demonstrated through stylized examples of alternative invasion control techniques.     

Partial equilibrium approach to the free-rider problem

Groves and others have shown that truthful answers concerning preferences for public goods can be elicited as dominant strategies if appropriate tax-subsidies rules are applied. This paper studies the statistical properties of the total revenues generated by one of the mechanisms with this desirable dominant strategy property. For particular specifications, it is shown that the expected total revenues increase like √N. Further, if these revenues are rebated equally to the individuals in the model, then, although the dominant strategy property no longer obtains, the optimal responses converge to the truth in large economies. As a result, it can be shown that the mechanism with rebates will make the Pareto optimal decision with arbitrarily high probability, provided that the willingness to pay distribution is assumed to be symmetric.     

Spatially optimal habitat management for enhancing natural control of an invasive agricultural pest: Soybean aphid

By their direct effects on private profitability, invasive agricultural pests create special incentives for management that set them apart from other categories of invasive species. One attractive nonchemical management approach for agricultural pests relies upon biological control by natural enemies. By improving the habitat of natural enemies of invasive agricultural pests, biological pest control can become privately attractive. This study develops a spatial optimization model to explore economically optimal spatial configuration of natural enemy habitat in agricultural landscapes. The model is applied to the management of soybean aphid (Aphis glycines), a recent invasive pest species of soybean production systems in the North Central region of the United States. Results indicate that non-crop habitat management can be a promising pest management option for organic cropping systems. Under current prices, however, habitat management tends to reduce net returns for conventional farms. Both area and configuration of non-crop habitats affect economic performance, with the greatest value coming from small, scattered areas of habitat.     

Theoretical incentive properties of contingent valuation questions: Do they matter in the field?

Green et al. (1998) [Green, D., Jacowitz, K.E., Kahneman, D., McFadden, D., 1998. Referendum contigent valuation, anchoring, and willingness to pay for public goods. Resource and Energy Economics 20 (2), 85−116] show theoretically that stated preference questions about public services can be framed in such ways that if the subjects accept the frame the payoff­maximizing behavior will be to answer truthfully. One key element of such a theoretically incentive­compatible framing is that the (hypothetical) decision rule specified in the survey instrument is understood to be a majority rule rather than the efficiency rule typically used in cost­benefit analysis. We conducted field experiments in Germany and Switzerland to test if a referendum framing as suggested by Green et al. is effective in reducing strategic misrepresentation in a contingent valuation setting. We did not find the expected effects of the framing treatments on stated willingness to pay or on individuals' (stated) beliefs about the social choice context. The results do not support hopes that a theoretically incentive compatible framing could be purposefully used to invoke the specific beliefs about the linkage between responses and policy implementation that would make stated preference questions incentive compatible.     

Valuing the potential economic impact of climate change on the Taiwan trout

The purpose of this study is to estimate the value of the potential economic impact of climate change on the Taiwan trout (also referred to as Oncorhynchus masou formosanus), an endangered species that only lives in high mountain stream sections in which the water temperature is lower. A two-stage approach is adopted to estimate the value of the change in the Taiwan trout stock due to a change in climate. The first stage involves establishing the relationship between the Taiwan trout stock and climate change, while the second stage involves estimating the non-market value of the change in the Taiwan trout population using the double bound model associated with the contingent valuation method (CVM). Our results indicate that the total Taiwan trout population will decline from 1612 to 974, 560, and 146 if precipitation in Taiwan increases by 0.6 mm/day, while the temperature increases by 0.9 °C, 1.8 °C, and 2.7 °C, respectively. The mean willingness to pay per person per year to avoid a change in the trout stock caused by climate change is found to be US$16.22, US$25.72, and US$33.60, respectively.     

On the willingness to pay to reduce risks of small losses

While willingness to pay is a common concept to measure the benefit gained from a reduction in the probability of loss, it is still questionable how it is linked to risk aversion and risk elimination behaviors, and how it is affected by the presence of an exogenous source of risk. By focusing only on risks of small losses, this article sheds light on these three issues and provides new results on the determinants of the willingness to pay.      

谨防物种地理入侵维护区域经济可持续发展

人类历史上外来物种的地理引入对区系经济发展有过积极的作用,由于物种地理引入过程中的“入侵”机制,使得引入种不但不能增加原生地生物区系的物种种类,反而减少了它的生物多样性,加速了原生生物区系的物种灭绝速度,引发水土流失,恶化人类生存环境,增大难以逆转的经济损失隐患,进而制约区域经济的可持续发展,对区域经济可持续发展可能会造成严重的潜在危害。为了维护区域经济的可持续发展,必须谨防物种地理入侵。