Optimal Regulation of Invasive Species Long-Range Spread: A General Equilibrium Approach

1 Introduction

The movement of invasive species into territories outside a species biological spread rate is often due to economic activity and has been known to increase the likelihood of invasion success (Wilson et al. 2009). Examples of human-induced invasive species spread include the Burmese python, a reptile currently altering the Florida Everglades ecosystem and spreading through the exotic pet trade (Reed 2005); the zebra mussel, a small mussel damaging economic structures and the ecosystem in the Great Lakes region and spreading through infested boats’ ballast water (Griffiths et al. 1991); and the emerald ash borer (EAB), a beetle threatening North America’s ash trees and spreading through infested firewood and on the wind currents of cars (Prasad et al. 2010). The increased rate of long-range spread is troubling; invasive species cause $120 billion in economic and ecosystem damages in the United States annually (Pimentel, Zuniga, and Morrison 2005). To reduce damages from invasive species, economic instruments can be implemented to help minimize the long-range spread of invasive species.

Current policies are in place to help minimize the damage caused by the introduction of invasive species from economic activity. Such policies include specific taxes, which are charged as a fixed amount on the sale/consumption of each specific unit of a good/service, and ad valorem taxes, which are levied on economic activity according to its value. These market mechanisms are typically applied to alter incentives (prices) and change human behavior, which reduces economic activity that contributes to the long-range spread of invasive species.

Specific taxes have been used by the states of Hawaii, Tennessee, and Maryland as well as by the federal government for controlling the spread of various invasive species. To aid in the state’s fight against invasive species, Hawaii implemented an Invasive Species Prevention Act in 2008, which levies a 50-cent tax on every 1,000 pounds of goods shipped via air cargo (Kim 2008). Tennessee has introduced the “Iris Tag,” a license plate depicting the state’s cultivated flower, which can be obtained by a Tennessee resident for an additional charge (Tennessee State Parks 2011). Maryland, through its Forest Stewardship Program, provides financial assistance, including a property tax reduction of about $150 per acre, to help preserve and restore private property to its natural state^[1] (Maryland Department of Natural Resources 2011). The Forest Stewardship Program includes financial assistance for invasive species management. Similarly, The U.S. Fish and Wildlife Service impose fixed excise taxes on hunting and fishing equipment.

Ad valorem taxes/subsidies are also a popular tax instrument and are currently used in Florida, Idaho, Oregon, Montana and Wisconsin. The 2010 Florida Statutes detail an Everglades Agricultural Privilege Tax in and around the Florida Everglades, which is levied on agricultural property for Everglades improvement and management, including the control of invasive species (Florida 2011). Idaho uses a tax instrument that is most similar to an ad valorem tax: The state requires boaters to contribute to the Idaho Invasive Species Fund by purchasing a permit based on the size of their boats (kayaks versus motorboats) (Idaho State Parks and Recreation 2011). Both Oregon and Montana have implemented similar permit requirements for boaters (Oregon 2010; Montana 2002). Wisconsin currently has a Managed Forest Law through the Living Forest Cooperative, which assists with the management of invasive species in forest areas Michigan Department of Agriculture (2013). This program offers a deferment of the forest owner’s property taxes if the owner prepares a sustainable forest management plan with a certified plan writer.^[2]

When applied correctly, specific and ad valorem taxes help regulate market failures, including ecosystem externalities resulting from the economic movement of invasive species (Koenig 1985; Crocker and Tschirhart 1992; Pirttilä 2002). However, these market mechanisms are often created under a great deal of uncertainty, including uncertainty in economic damages, control costs and how the invasive species interacts with the native ecosystem (Mehta et al. 2007; Eiswerth and Van Kooten 2002; Keen 1998). Further, little research has been done to determine the efficiency of these policies under economic and ecological uncertainty when multiple market failures exist (Richards et al. 2010; Goulder et al. 1999; Grant and Quiggin 1997).

To address this issue, I develop a general equilibrium model that is capable of evaluating optimal regulations of market failures caused by invasive species. The model accounts for feedback loops that exist between economic production, natural resource stocks, and invasive species populations. A key natural resource and the associated invasive species are modeled as an interdependent system. The invasive EAB is used as an example to determine the optimal specific and ad valorem taxes for minimizing the associated ecosystem externalities. Specific and ad valorem taxes are then compared. Important results suggest that specific taxes rely on fewer economic and ecological parameters, making them more robust to uncertainty. Additionally, although only one invasive species is considered, the results show that multiple instruments are necessary to correct for multiple forms of invasive species transmission. Although specific taxes are preferred due to uncertainty and distortionary effects, a combination of specific taxes and ad valorem taxes could be implemented to achieve a Pareto optimal outcome. Finally, this methodology is general enough that it could be applied to other serious invasive species such as the Asian longhorned beetle^[3] or other non-borer pests (for example, see Aukema et al. 2011).

2 Application to EAB

Invasive forest insects, specifically wood-boring insects, account for the largest economic damages of all invasive species. Wood-boring insects reduce the value of residential property by $830 million annually and cost local governments $1.7 billion annually. The EAB accounts for the largest share of this damage, including annual residential property loss totaling $380 million and annual local government expenditures totaling $850 million (Aukema et al. 2011).

Since its initial detection in Michigan in 2002, the EAB has killed millions of ash trees in the Midwest and, more recently, New England (USDA Forest Service 2008). Scientists believe this beetle, which was introduced from Asia, was transported through solid wood packing materials in cargo ships and on planes. Most notably, the EAB has the capacity to kill an adult ash tree within 3–5 years and saplings within 1 year by feeding on the inner bark (Poland and McCullough 2006).

The EAB spreads locally through flight; economic activity, including driving and ash timber harvesting; and leisure activities such as camping, firewood gathering, and gardening with infested nursery trees (Prasad et al. 2010; Poland and McCullough 2006). Economic activity leads to hundreds of new introduction points and is likely to blame for the blanket of infestation now seen in southeastern Michigan (BenDor et al. 2006; Prasad et al. 2010). For instance, on their own, EABs can move an average of 9.84 km/year; however, they are currently moving over 20 km/year (Taylor et al. 2006). Most recently, Greene and Ulster counties in New York have confirmed EAB infestations, yet the closest EAB-infested county is Steuben County, New York, which is over 350 km away (NYS Dept. of Environmental Conservation 2013). This distance is well beyond the EAB’s ability to fly, suggesting economic activity is contributing to the EAB’s spread.

The current policy that is used to mitigate or slow the spread of the EAB is quarantine. This policy prohibits any ash tree movement outside a confirmed EAB-infested county, and it may actually contribute to ash tree mortality. Under the quarantine, it is legal to move ash trees within and between adjacent quarantined areas, which results in an increased risk of ash tree death in the quarantined county by intensifying the spread of the EAB. Random firewood inspections are established throughout EAB-infested areas to ensure that the quarantine is followed. The state of Michigan levies fines at a rate of $1,000–$250,000 and up to 5 years in jail for the movement of regulated ash tree materials MDARD (2014). In addition to quarantines and inspections, the state of Ohio destroyed all ash trees within an 800-meter radius of an infested tree. This costly practice was suspended in 2006, when the EAB was discovered in numerous ash tree stands.

Quarantine inspections and infested tree removal address local biological spread rates and do not address long-range economic dispersal, as both inspections and tree removal require detection of the EAB prior to implementation. This is troubling because there is a 1-year time lag between infestation and possible detection.^[4] Prior to detection and quarantines, economic activity is free to move ash wood that potentially carries the EAB. Therefore, quarantines and tree felling help contain only short-range biological and economic spread once the EAB has been detected. It is imperative to implement policies that address both long- and short-range dispersal because once an area is infested with the EAB, there are almost no effective options for eradication, and EAB-related damage will likely ensue.

3 A General Equilibrium Model: Theory

The EAB provides an example of human-induced invasive species spread where movement in and around an EAB-infested area accelerates the rate at which the EAB spreads. This outside movement of EAB in turn degrades ash-resource-dependent economic activity and poses health risks from falling dead ash trees. In this sense, invasive species like the EAB are an environmental externality that operates through interdependent economic–ecological relationships (Figure 1). Using a steady-state general equilibrium analysis following Crocker and Tschirhart (1992),^[5] control techniques in the form of taxes/subsidies on economic activity known to contribute to the spread of EAB are examined. This model pays special attention to the predator–prey relationship of EAB and ash trees and the ecological consequences from economic activity.^[6]

Figure 1:

Ecosystem and economic model flow chart.

The theoretical economy consists of ash tree-dependent production and a representative consumer who derives utility through ash resource services, a composite good, and leisure. A predator–prey ecosystem models the relationship between ash tree population and EAB, where leisure and harvest of ash trees contribute to the growth of EAB. The ash resource-dependent economic activity and consumer utility link the economic and ecosystem services. The ecosystem is introduced into the economy through the harvest equation for ash trees.

The representative consumer in the model derives utility through ash tree harvests, ha, ash tree stock in the form of indirect use values for yard/forest quality, a, and a composite good, x. The consumer also participates in leisure either within the household, h, or outside the household, oh. Leisure is broken down into two categories because within household activities, h (such as watching TV) do not contribute to the spread of EAB, whereas driving and outside activities necessary for oh do contribute to EAB spread. The twice differentiable utility function is given by eq. [1] such that all goods generate positive utility at a decreasing rate, Ui>0,Uii<0, where i=ha,a,x,oh,h

Economic activity occurs within two industries in the economy, harvest of ash trees (used for either landscape purposes or timber production) and a composite good. Equation [2] represents a quasi-concave production function, Ha, for ash tree harvest, which is a function of ash tree stock,a, and labor in the harvest sector,Lh

Ash trees and labor positively impact the harvest production function, ∂Ha∂a=Haa,∂Ha∂Lh=HLha>0, where subscripts denote partial derivatives.

Composite good production is achieved through the use of labor, Lx, and a quasi-concave production function, X

As previously mentioned, a consumer derives utility from the non-consumptive use of ash trees, which can be interpreted as yard/forest quality. Ecosystem equations describing ash and EAB growth are introduced to account for the non-consumptive use of ash. For the clearest exposition of the tradeoffs involved assume ash and EAB stocks are in steady state such that net growth equals harvest as represented by eqs [4] and [5], respectively.

Assuming silviculture, the growth of ash trees, A, is a function of labor spent planting new ash trees, La, current ash stocks, a, and EAB, e. Labor in silviculture increases ash stock, ∂A∂La=ALa>0 as does density-dependent growth, ∂A∂a=Aa>0. EAB kills ash by destroying its ability to transfer water and nutrients, so ∂A∂e=Ae<0:

EAB growth is an increasing function in leisure and labor in the ash tree harvest sector because driving and movement around/in an EAB infested area spreads the EAB more quickly than it would naturally, ∂E∂oh=Eoh,∂E∂Lh=ELh>0. EAB spread rates from economic activity are uncertain, which is accounted for in the model by the normalized exogenous probability that one unit of economic activity will lead to one EAB introduction. The probability that outside leisure (from here on referred to as simply leisure) and ash tree harvest introduce an EAB is γ, σ, respectively, where 0≤γ,σ≤. Given this, γ∗oh and σ∗Lh are the expected number of EAB introductions from economic activity. Higher levels of ash tree stocks and EAB stocks increase the growth of EAB, ∂E∂a=Ea,∂E∂e=Ee>0:

Finally, the labor resource constraint is represented by

where Lˉ is the total available labor supply.

The ecosystem and economy are linked through changes in ash tree and EAB population, which directly impacts consumer utility and indirectly adjusts ash tree stocks where increases in EAB will decrease the amount of ash trees available for harvest.

4 Policy Results

Economic instruments in the form of taxes/subsidies are introduced as a corrective market mechanism to ensure that the externality of economic activity on invasive species is internalized by the firm and the consumer. As mentioned above, current EAB policies address only short-range dispersal. The policies created here attempt to address long-range EAB dispersal through economic activity because the unregulated competitive equilibrium suggests that consumers are participating in more EAB spreading activities than the centralized equilibrium. As a result, tax/subsidy policies adjust prices, and consequently behavior, which lead to less EAB spreading activity and/or more of the composite good or home leisure consumption. Similar corrective instruments have been applied to forest externalities in a partial equilibrium context (Englin 1990; Koskela and Ollikainen 2001). The two most widely used policy options among jurisdictions are considered, specific and ad valorem taxes.

4.1 Specific Taxes

Specific taxes can be levied on harvest and leisure at rates τh and τoh and attached to eqs [11] and [12].^[8] Taxes on leisure would occur as taxes on goods/services known to be complementary to leisure outside the household as is assumed with a Corlett–Hague rule (Gordon 1988; Pirttilä 2000).^[9] The decentralized solutions would take the form

[17]UhaUx=XLx1ALa+1HLha+τhpx

and

[18]UohUx=XLx+τohpx.

The solutions for the optimal taxes on harvest and leisure that would ensure a Pareto optimum are then calculated as

[19]τh=−pxσELhη

[20]τoh=pxγHLhaEohη.

An additional policy consideration includes taxing labor in harvest instead of harvest output. If instead specific taxes were levied on labor in harvest at the rate τa, the decentralized solution would take the form

[21]UhaUx=XLx1ALa+1HLha+τapxHLha

with a corresponding tax of

[22]τa=−pxσELhHLhaη.

If each of the ecological and economic partial derivatives was known, then the centralized solution would equal the decentralized solution, as demonstrated in Figures 2 and 3. Taxing harvest or labor associated with harvest would produce an efficient allocation, as shown in Figure 4. Taxing labor or harvest output produces the same social optimum but provides the regulator more flexibility if they have varying levels of information on labor or harvest level.

Figure 2:

Unit tax on harvest. This figure represents the invasive species externality in a decentralized and centralized framework assuming a negative invasive species externality. Curve ac represents attainable production, while the other curve is the consumer’s indifference curve. Line de is the price system in the market. Graph (a) represents the unregulated decentralized consumption of harvest, in which the firm fails to internalize the invasive species externality. As such, there is a demand surplus of harvest (g) and a supply shortage of the composite good (f) and a Pareto-efficient allocation fails to exist. Through unit taxes on harvest, or labor in harvest, the price system and the consumer adjust such that a decentralized solution equals a centralized solution where the MRS = MRT as in (b).

Figure 3:

Unit tax on leisure outside the home. This figure represents the invasive species externality in a decentralized and centralized framework assuming a negative invasive species externality. Curve ac represents attainable production, while the other curve is the consumer’s indifference curve. Line de is the price system in the market. Graph (a) represents the unregulated decentralized consumption of leisure, in which the consumer fails to internalize the invasive species externality. As such, there is a surplus of demand of leisure (g) and a supply shortage of the composite good (f) and a Pareto-efficient allocation fails to exist. Through unit taxes on harvest, or labor in harvest, the price system and the consumer adjust such that a decentralized solution equals a centralized solution where the MRS = MRT as in (b).

Figure 4:

Ad valorem tax on harvest and leisure outside the home. This figure represents the invasive species externality in a decentralized and centralized framework assuming a negative invasive species externality. Curve ac represents attainable production, while the other curve is the consumer’s indifference curve. Line de is the price system in the market. Graph (a) represents the unregulated decentralized consumption of harvest, in which the firm fails to internalize the invasive species externality. As such, there is a surplus of demand of harvest (g) and a supply shortage of the composite good (f) and a Pareto-efficient allocation fails to exist. Through ad valorem taxes on harvest, or labor in harvest, the price system and the consumer adjust such that a decentralized solution equals a centralized solution where the MRS = MRT as in (b). Figures (c) and (d) follow the explanation above.

Both the producer and consumer taxes are inherently complicated and are increasing in the fraction of economic activity contributing to EAB population and the consumers’ willingness to pay for improved ash quality. To determine the sign of the tax (tax or subsidy), the ecosystem externality must be signed, which is difficult because it includes adjustments throughout the entire ecosystem. Normalized by the price of the composite good, the relative difference of the partials in the ecosystem externalities will determine the sign of the tax on harvest and leisure.

An externality greater than zero (i.e. an increased marginal benefit from harvest and increased marginal cost from leisure), η>0, requires that the denominator of the externality is negative such that there is a reduction of ash stock due to EAB infestation, ALaEe<σAeELh and that the harvest benefits from an increase silviculture (ash growth) outweigh harvest benefits from an increase in labor HLhaAaEe−AeEa<HaaσAeELh+ALaEe. If η>0, it follows that taxes on harvest and harvest labor are negative (subsidy), τh=−pxσELhη>0 and τa=−pxσELhHLhaη>0; while the tax on the consumer is a positive (tax), toh=pxγHLhaEohη>0. In this scenario, the economy is consuming too much leisure and not enough harvest relative to the Pareto optimal outcome. As a result, a subsidy on harvest and a tax on the leisure will result in a Pareto optimal outcome.

An externality less than zero (i.e. an increased marginal cost from harvest and increased marginal benefit from leisure), η<0, requires a positive denominator in the externality. This could occur in one of two ways. One possibility is that the benefits from silviculture outweigh the increase in EAB due to harvesting ash trees, ALaEe>σAeELh. Alternatively, a positive denominator could occur when there is a reduction of ash stock due to EAB infestation, ALaEe<σAeELh, and the harvest benefits from an increase in labor outweigh the harvest benefits from an increase silviculture (ash growth) HLhaAaEe−AeEa>HaaσAeELh+ALaEe. If η<0, it follows that taxes on harvest and harvest labor are positive (tax), τh=−pxσELhη>0 and τa=−pxσELhHLhaη>0; while the tax on the consumer is negative (subsidy), toh=pxγHLhaEohη<0. In this scenario, the economy is producing more harvest and less leisure than the Pareto optimal outcome. As a result, a tax on the harvest and a subsidy on leisure will result in a Pareto optimal outcome.

4.2 Ad Valorem Taxes

If ad valorem taxes, charged as a percentage of the value, were levied on harvest (or labor) at a rate of th (or ta) and leisure at a rate toh and attached to eqs [11] and [12], the decentralized solutions would take the form^[10]

[23]UhaUx=XLx1ALa+1HLha11−th

[24]UohUx=XLx1+toh.

The corresponding taxes are

[25]th=σELhηALaHLhaσELhηALaHLha−ALaXLx−HLhaXLx

[26]toh=γHLhaEohηXLx

Though this ensures that the producer and consumer internalize the externality as shown in Figure 3, this tax structure creates a distortionary effect on inside leisure, h, as shown in Figure 5:

[27]UhUx=XLx1+toh≠XLx

Figure 5:

Ad valorem impact on leisure inside household. This figure represents the impact of the invasive species taxes in a decentralized and centralized framework assuming a negative invasive species externality. Curve ac represents attainable production, while the other curve is the consumer’s indifference curve. Line de is the price system in the market. Graph (a) represents the unregulated decentralized consumption of within household leisure, in which the household consumption of h is socially optimal or MRS = MRT. In (b), once ad valorem taxes on harvest, or labor in harvest, are introduced (shown in Figure 3) the price system and the consumer adjust such that a decentralized solution no longer equals a centralized solution. As such, there is excess demand/supply of harvest (g) and excess demand/supply of the composite good (f) and a Pareto-efficient allocation fails to exist.

This distortionary effect occurs because taxes on oh enter the model in the form of an income tax in which h is also impacted (Bovenberg and De Mooij 2004). This differs from the unit tax because the ad valorem tax is based on the value of oh or wage × oh. However, if it was possible for the government to only tax oh, then there would not exist distortionary effects on h. For example, if EAB spread specifically through the movement of cars, then a car property tax would target oh, leaving h unaffected.

Additionally, policy makers could consider taxing labor in harvest instead of harvest output. If instead ad valorem taxes were levied on labor in harvest at the rate ta, the decentralized solution would take the form^[11]

[28]UhaUx=XLx1ALa+1HLha1+ta

[29]ta=−σELhηALaHLhaXLx(ALa+HLha)

The interpretation and signing of the ad valorem taxes is slightly more complicated as the ad valorem tax relies on more information about the partial derivatives and generates a distortionary effect on leisure inside the household. However, interpretation could be similarly followed in that a positive tax on harvest would reduce EAB spreading economic activity from harvesting ash trees, a positive tax on leisure would reduce leisure outside the home diminishing EAB spread from leisure. Alternatively, a negative tax (or subsidy) would increase EAB spreading economic activity because the economic benefits outweigh the ecological costs.

5 Discussion

For this analysis, policy makers are able to address the producer externality with the choice of taxes imposed on harvest output or labor devoted to harvest. Either of these taxes, when used in conjunction with a tax on leisure, achieves a Pareto-efficient outcome, assuming policy makers can specifically target oh in the ad valorem taxes. However, in practice, the counteractive and indirect impacts from economic activity within the interdependent system make it difficult to formulate a definitive tax schedule. To do so, each partial derivative must be known, which requires a detailed knowledge of economic and ecological relationships. Comparing the specific taxes in eqs [19], [20], and [22] to the theoretical ad valorem taxes in eqs [25], [26], and [29], it is clear that the ad valorem taxes rely on more of the parameters from both the economic and ecological functions. As a result, the specific taxes would be preferred under a case of imperfect information or uncertainty over the parameter values.

While I address the various taxes separately, it would also be possible for a policy maker to combine the economic instruments and still achieve Pareto optimum. For example, it may be easier to tax leisure in the form of income or property taxes, which are often in the form of ad valorem taxes. However, a jurisdiction may prefer to tax logging output per board feet rather than using an ad valorem tax on harvest labor or the value of the harvest output. As shown in the introduction, jurisdictions prefer to use both specific and ad valorem taxes for invasive species policy. As a result, it is possible to present a tax menu to policy makers and allow jurisdictions, with varying laws and limitations, to implement a first-best tax schedule.

Introducing multiple market instruments for multiple market failures is an important considering for invasive species policy going forward. This becomes more important as the expected number of invasive species introductions from economic activity increases. A natural question arises, what if only one policy, either a tax on harvest/labor or leisure, can be implemented? Though welfare ranking is outside the realm of this paper, several observations can still be made. Under specific taxes, if the regulator was only able to implement one tax on either harvest or leisure, the second best solution would never equal the first-best, or the two-tax system. The impact from implementing only one ad valorem tax is uncertain given the distortionary impacts resulting from the ad valorem taxes on leisure outside the household because an ad valorem tax on oh will produce an efficient amount of oh, but impacts the consumption of h as seen in Figure 4. A welfare measurement or a way to rank welfare levels is needed to understand the distortionary impacts, which would be a valuable extension.

6 Concluding Remarks

This paper considers possible corrective mechanisms for invasive species long-range spread. Using the EAB as a case study, policies considered include specific and ad valorem instruments. Such policies are affected by the fraction of economic activity contributing to the spread of EAB and the consumer’s willingness to pay for ash quality. The theoretical model also addresses the importance of having a combination of policies for dealing with multiple forms of long-range transmission. Although the model considers a single invasive species, multiple policies are required to fully internalize the ecosystem externalities. Specifically, the EAB is introduced into the ecosystem via labor devoted to harvest and leisure outside of the home. As the specific and ad valorem taxes show, two taxes, one tax on harvest output or labor in the harvest sector and one tax on leisure, are required for the decentralized solution to equal the centralized solution; one tax will not suffice.

The simple theoretical model shows that the implementation of market policies can achieve a first-best outcome. Should the policy maker face uncertainties in various parameters, the specific taxes may be preferred over ad valorem tax to achieve an efficient first-best scenario, as it relies on fewer parameters from the ecological/economic equations. Likewise, specific taxes may be the easiest to implement in terms of the necessary calculations. This model has shown that a combination of tax options could be presented to the policy maker in order to achieve a social optimum.

There are some limitations to the modeling approach. First, I only consider specific and ad valorem taxes. Future research could benefit from examining other possible corrective mechanisms such as tradable permits, a two-part tariff, and quadratic taxes. Richards et al. (2010) have shown that quantity-based instruments, such as tradable permits, can be superior to price-based instruments for invasive species control policies, although few real-world applications exist.^[12] Two-part tariffs, such as implemented by Fullerton and Wolverton (2005), can be explained as a “deposit-refund” system, in which a dirty (polluting) product is taxed and a clean (nonpolluting) product or service is subsidized. Kossioris et al. (2010) illustrate that while specific, ad valorem, and quadratic taxes converge to a social optimum when correcting a common pool resource, a quadratic tax leads to an improvement in welfare. Second, I assume the taxes are only enforced on economic activity that introduces invasive species. Alternatively, future research could examine the benefits of taxing the forest managers who directly oversee trees impacted by EAB. For example, with the introduction of EAB, it may be socially optimal to remove, destroy, or replace the ash trees sooner than the forest manager would choose on their own. As a result, the removal of trees would prevent or limit the occurrence of ecosystem externalities [for additional examples, please see Englin (1990) and Koskela and Ollikainen (2001)]. Third, my model considers exogenous risk only. However, incorporating endogenous risk into the model would be a worthwhile exercise, as individuals invest in self-protection and self-insurance actions to minimize losses caused by invasive species.^[13] Fourth, while a steady-state model is good for initial intuition into this problem, a dynamic model would be a useful contribution to the current literature, along with an empirical application capable of ranking the welfare derived from each policy. Finally, though this model specifically addresses EAB, the application of the techniques could be extended to additional invasive species and future beetle outbreaks.