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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
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Title of Proposal: The Economics and Ecology of the Risk of Invasive Plant Establishment from
the Horticultural Trade in North America
Program to Which Application being Made: “PREISM”
Priority Research Area: II. Practical Decision Analysis for Invasive Species Management
Principal Investigator/Project Director: Edward B. Barbier, John S. Bugas Professor of
Economics, Department of Economics and Finance, University of Wyoming.
Co-Investigators:
Professor Duncan Knowler, School of Resource and Environmental Management, Simon Fraser
University.
Professor Sarah Reichard, Center for Urban Horticulture, College of Forest Resources,
University of Washington.
Type of Institution: University of Wyoming (Land Grant University)
Contact Numbers:
Prof. E. Barbier: Phone (307) 766 2358; Fax (307) 766 5090; E-mail [email protected].
Prof. D. Knowler: Phone (604) 291 3421; Fax (604) 291 4968; E-mail [email protected]
Prof. S. Reichard: Phone (206) 616 5020; Fax (206) 685 2692; E-mail
[email protected]
Signature of Principal Investigator:…………………………………………………...…
Date:…………..
Signature of Authorized University of Wyoming Representative:…….…………….…
Date:…………..
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Table of Contents
Project Summary
PROJECT DESCRIPTION
1
Rationale and Significance
3
Research Methods
6
Research Tasks
7
Conclusion
12
Citations to Project Descriptions
Collaborative Arrangements
Vitae and Publication Lists for Project Staff
Budget (Forms ARS-455 –9 pages)
Indirect Cost Rate Schedule
Current and Pending Support
Additions to Project Description: reprints
Knowler, D. and Barbier, E.B., 2005, “Importing Exotic Plants and the Risk of Invasion: Are
Market-Based Instruments Adequate?” Ecological Economics 52:341-354.
Knowler, D., 2005, “Reassessing the Costs of Biological Invasion: Mnemiopsis leidyi in the
Black Sea,” Ecological Economics, 52:187-199.
Barbier, E.B. and Shogren, J.R. 2004. "Growth With Endogenous Risk of Biological
Invasion." Economic Inquiry 42(4):587-601.
Barbier, E.B., 2001, "A Note on the Economics of Biological Invasions," Ecological Economics,
39(197-202.
Reichard, S.H. and White, P., 2001, “Horticulture as a Pathway of Invasive Plant Introductions in
the United States,” 51(2):103-113.
Reichard, S.H. and Hamilton, C.W., 1997, “Predicting Invasions of Woody Plants Introduced into
North America,” Conservation Biology, 11(1):193-203.
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Project Summary
The proposed research aims to develop an integrated economic and ecological analysis of
the costs and benefits associated with the risk of invasive plant establishment from the
horticultural trade in North America. The research will encompass:
(1) Modeling the economic behavior of a profit-maximizing horticultural industry that
imports an exotic plant species through establishing nurseries at specific geographical
locations in North America.
(2) Ecological and economic analysis of the risk and potential damages from accidental
introduction and establishment of invasive plant species associated with a commercial
plant industry that imports and breeds exotic plant species at its various locations.
(3) Integrating these economic and ecological analyses to model the potential policy
tradeoff between the profits of the commercial plant breeding industry with the
expected losses associated with the risk of accidental introduction.
(4) Evaluation of various policy interventions for reducing the risk of accidental
introduction by the North American horticultural industry; for example, these might
include: “doing nothing”, self-regulation by the industry, taxing or banning the sale of
exotic species and policy coordination between the US and Canadian governments.
The overall objective of the project is to produce a new ecological-economic method of
assessing the commercial decision of private nurseries in the US and Canada to sell exotic
species and the accompanying risk of accidental introduction. Such research is of increasing
importance to improve policies to control this problem in both countries and to decision makers
seeking new tools and modelling methods to assist in the design of better policies.
Principal Investigator/Project Director: Edward B. Barbier, John S. Bugas Professor of
Economics, Department of Economics and Finance, University of Wyoming.
Co-Investigators:
Professor Sarah Reichard, (College of Forest Resources), University of Washington.
Professor Duncan Knowler, School of Resource and Environmental Management, Simon Fraser
University.
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Project Description
1. Introduction
The proposed research aims to look at the ecology and economics of the risk of invasive
plant establishment from the horticultural trade in North America.
Non-indigenous, or "exotic" plant species are often intentionally imported into regions
outside of their normal range as plant or breeding stock for agricultural, horticultural or domestic
gardening activities. However, one of the unintended side effects of such introductions is that
the exotic plant species may be accidentally introduced into the wider environment of the new
host region, with dramatic impacts.
For example, the cumulative losses to the U.S. economy from invasive plants have been
estimated at $600 million over the period 1906 to 1991 (OTA, 1993). Recent estimates suggest
that the annual losses from invasive plants in the U.S. may be even larger (Pimental et al. 2000).
In Canada, recognition that invasive exotic plants could have a significant economic and
ecologic impact began with the instigation of a national awareness program for purple loosestrife
in 1990 (Haber 1998). Recent surveys of plant invasions suggest the cumulative damages
inflicted non-native invaders are comparable to damages in the US (Haber 2002; Claudi 2002).
Economic analysis of the problem of invasive species is emerging as a new area of
interest among environmental economists, as demonstrated by a spate of recent works on the
subject (Perrings et al., 2002; Barbier, 2001; Barbier and Shogren, 2004; Eisworth and Johnson
2002; Naylor, 2000; Knowler and Barbier, 2000; Settle and Shogren 2002). In most treatments of
the economics of invasion, the invasive species is seen as imposing costs without contributing
any benefits in return. This approach accords with the standard treatment of a pollution problem,
and results in policy prescriptions that tradeoff residual pollution damages against the costs of
control, settling at equilibrium on a mix that maximizes social welfare, usually by minimizing
damages plus control costs.
However, the economic analysis of plant invasions needs to be modified in the case for
exotic species that have been deliberately introduced, as typically there was some perceived
benefit for their introduction in the first place. This potential benefit adds an additional element
not taken into account in the growing literature on the economics of biological invasions. For
instance, horticultural operations such as nurseries may find it profitable to import, breed and sell
exotic species since they can earn profits from doing so, even though the plant may become
invasive and incur damages and control costs as a result. Thus, prohibiting sale of the exotic has
social costs in the form of foregone consumer benefits and nursery profits, and these must be
considered in a proper analysis of the economics of invasion if it is to serve as a practical guide
to policies and decisions concerning management of the plant invasive problem. For example,
Claudi (2002) notes that, prior to the 1996 ban on sales of Lythrum cultivars in Manitoba, annual
garden nursery revenues from sale of loosestrife cultivars in the province were CAN$10,000 per
year.
A principal contribution of the proposed research is therefore to demonstrate the
development of such a practical decision analysis of the costs and benefits associated with the
possible accidental introduction and establishment of plant invasives through commercial
horticultural operations.
Preliminary economic analyses by two of the researchers involved in this proposal
develop and use such a cost-benefit framework to examine policy options to regulate the
commercial horticultural decisions to import exotic plant species (Barbier and Knowler 2005;
1
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Knowler and Barbier 2005). This initial work has identified two additional features of the
invasive plant problem associated with the commercial horticultural trade that must be
considered in any economic analysis in support of practical decision-making for managing this
problem.
First, the decision by the commercial nursery to import, breed and sell an exotic plant
species is taken ex ante of any knowledge of a possible threat of invasion and its consequent
economic losses. That is, the likelihood and timing of any future invasion are unknown and thus
revealed only ex post. Given this uncertainty, the economic assessment of the threat of plant
invasion must be concerned with analyzing the potential unintended risk of introduction
associated with private nursery operations benefiting from sales of exotics.
Second, better assessment of the commercial decision of private nurseries to sell exotic
species and the accompanying risk of accidental introduction requires improvements in
integrating ecological-economic modeling. This approach is necessary because the problem of
invasive species introduced through commercial sale is fundamentally economic and ecological.
For example, as noted above, although many exotic species are imported, bred and sold by
horticultural operations throughout North America relatively few have become established
successfully as invaders in their host environment, and not all of the successful invaders have
caused widespread economic damage. To determine the potential risk of future unintended
introductions via the horticultural trade it is necessary to know: a) the key characteristics of
various exotic species that make them more likely to become successfully established in North
American environments and b) the key environmental factors that contribute to the spread and
adaptation of plant invasives as well as their ability to displace native species and cause harmful
economic damages (Reichard and Hamilton 1997).
The proposed research aims to develop an integrated economic and ecological analysis of
the costs and benefits associated with the risk of invasive plant establishment from the
horticultural trade in North America. The research will encompass:
(1) Modeling the economic behavior of a profit-maximizing horticultural industry that
imports an exotic plant species through establishing nurseries at specific geographical
locations in North America.
(2) Ecological and economic analysis of the risk and potential damages from accidental
introduction and establishment of invasive plant species associated with a commercial
plant industry that imports and breeds exotic plant species at its various locations.
(3) Integrating these economic and ecological analyses to model the potential policy tradeoff
between the profits of the commercial plant breeding industry with the expected losses
associated with the risk of accidental introduction.
(4) Evaluation of various policy interventions for reducing the risk of accidental introduction
by the North American horticultural industry; for example, these might include: “doing
nothing”, self-regulation by the industry, taxing or banning the sale of exotic species and
policy coordination between the US and Canadian governments.
2
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
2. Rationale and Significance
2.i. General
Policymakers in North America face a critical tradeoff concerning the risk of accidental
introduction of plant invasions as a result of commercial horticultural operations.
Horticulture is a profitable and expanding industry. US floriculture and nursery crop
sales, based on growers’ wholesale receipts, topped $14 billion in 2002, a more than 50%
increase from a decade previously (Jerardo 2002). On average, a typical US household spends
$129 annually on these crops. In Canada, the value of direct ornamental and plant sales to the
public in 2003 was over CAN$290 million, also a significant rise over previous years (Statistics
Canada 2004).
As the North American horticultural industry continues to grow, new nursery locations
are being established. For example, a 2001 survey of floriculture growers in 36 US states
indicated that since 1992 the number of small growers (between $10,000 and $100,000 in annual
sales) has increased from 5,829 to 6,243, and the number of large growers (over $100,000 in
annual sales) rose from 4,566 to 4,722 (Jerardo 2002). About two-thirds of the growing area
utilized for floriculture crops comprises open fields, currently estimated at 41.1 million acres.
Most retail nurseries operate locally, and thus any potential risk of invasion may also be confined
to the immediate environment. However, some retail and many wholesale nurseries may sell
across the US, through the use of commercial shipping and postal mail order as well as internet
sales (Reichard and White 2001). The seed trade industry is also expanding rapidly in the US,
much of which is for horticultural uses. Seed producers tend to trade and ship across the US.
Thus the expansion of the horticultural industry and trade in North America carries a
large risk of invasive plant species establishment. For example, it is estimated that the
operations of the horticultural industry accounts for as much as 80-85% of woody plant invasions
and 60-65% of herbaceous invasions (Reichard and White 2001). The initial selection and
source of the plant, that is the choice of cultivars and breeding program, affects the level of plant
invasion. Moreover, the private purchase of plants from the horticulture industry fails to take
into account the external public cost that is incurred if and when these plants become invasive.
In assessing the increased risk and growing scale of the problem posed by the
introduction of plant invasives in the US, an Issue Paper by the Council for Agricultural Science
and Technology (Mullin et al. 2000, p. 4) concluded: “Although there are some federal
regulatory constraints on movement, sale, and possession of exotic organisms, the overall
resources directed at prevention, intervention, quarantine, removal, public awareness, and the
enforcement of existing federal statutes are seriously inadequate. Many states also have
regulations governing invasive plant species but these regulations are inconsistent from state to
state, may be confusing or contradictory, and do not adequately address the scope of the
problem.”
Similar conclusions have been reached in Canada about the inadequacy of existing
federal and provincial policies for managing the threat of plant invasions (Haber 2002; Claudi
2002).
Further research in the integrated ecology and economic modelling of the commercial
decision of private nurseries in the US and Canada to sell exotic species and the accompanying
risk of accidental introduction is therefore of increasing importance to improve policies to
control this problem in both countries. Moreover, such research is crucial at this time as the
current debate over what policy approaches to adopt to this problem considers a number of
3
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
possible alternatives: from “doing nothing” to self-regulation by the horticultural industry to
increased government and state regulation of the sale and distribution of exotic species.
The North American horticultural industry should also benefit from better policies to
manage the potential risk from the importing, breeding and sale of exotic plant species. By
reducing uncertainty in the industry over current and proposed regulations, improved polices will
enable the industry to make informed choices about how best to substitute non-invasive species
with potentially invasive ones in wholesale and retail operations. An effective policy would
ensure that this would meet the objective of reducing the risk of potential plant invasions without
affecting significantly the profits of the horticultural industry. In fact, as a recent study has
found, an effective policy that controls the sale of invasive plants by nurseries “could actually
stimulate sales, if handled correctly, because replacement plants would be promoted and sold”
(Reichard and White 2001, p. 111).
2.ii Examples of Plant Invasions from the Horticultural Industry
Both the United States and Canada face common ecological and economic impacts posed
by plant invasions, because these species spread rapidly across similar eco-zones in North
America. As noted by Haber (1998), most of the exotic species that have become invasives in
the northern latitudes of North America have originated from temperate zones of Europe and
Asia where the climate and eco-zones in Canada and the US is similar to that in their adopted
homelands. Moreover, the impacts of invasive plants, especially with regard to endangered and
threatened native plants in Canada, are most evident in eco-zones that “overlap” into Northern
US states (Haber 1998 and 2002; Claudi 2002).
Some of the most pernicious North American invaders are species that were introduced
deliberately through horticultural operations and trade. For example, the exotic perennial purple
loosestrife (Lythrum salicaria) invades wetlands, incurring lost forage and control costs of $45
million per year (ATTRA, 1996). As much as 3.24 million acres of wetlands in the US Midwest
are considered “highly susceptible to degradation” by purple loosestrife (Thompson et al. 1987,
p. 24). Similarly, the exotic saltcedar (Tamarisk spp) has invaded up to 23 states, disrupting
irrigation systems, hydropower generation, municipal water supplies and flood control
investments. One estimate puts the annual damages from this species alone at $121 to 291
million (Zavaleta, 2000).
Claudi (2002) has collated some of the available estimates for Canada’s most notorious
plant invasive species :
 Canada thistle: Wheat losses in Saskatchewan of CAN$3.6 million per year, and canola
crop losses and control costs of CAN$320 million per year for all prairie farmers.
 Leafy spurge: Impacts on cattle grazing of CAN$20 million per year in Manitoba.
 Knapweed: Economic impacts on rangeland in Western Canada of CAN$58 million per
year.
 Eurasian watermilfoil: Estimated annual aquatic weed clean-up costs of CAN$450,000
per year for the Okanagan-Basin Water Board of British Columbia.
 Purple loosestrife: Due to its ecological impacts, in 1996 Manitoba banned garden
nurseries from selling all Lythrum spp. cultivars.
In addition:
 Annual direct costs of knapweed species in Montana alone were estimated to be US$11.0
million (Hirsch and Leitch 1996).Aquatic weeds cost US$10 million in losses and
damages and US$100 million in control costs annually (Pimental et. al. 2000).
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Prof. Barbier, University of Wyoming,

Practical Decision Analysis for Invasive Species Management
Losses of pasture and range forage is estimated to be at least US$1 billion per year
(Pimental 1991).
2.iii. Current Policy Response for Preventing and Controlling Plant Invasions in North
America
The United States attempts to prevent entry of invasive plants by what is known as a
"dirty list" approach to intentional introductions. In other words, species are allowed to be
introduced into the country as long as they are not on a specific list of species known as the
"Noxious Weed List." Originally designated under the federal Noxious Weed Act, that list is
now maintained under the Plant Protection Act of 2000. Most of these species have already
proven to be a problem in some part of the country, but some are not known to be present and are
believed to be a potential threat. Under this Act movement of the listed species with the U.S.
borders is also prohibited.
National Management Plan, adopted in 2001, specifies that a more proactive screening
approach is needed and outlines necessary steps. It should be noted that actions in the Plan are
behind schedule, but on December 10, 2004, the Federal Register published Docket No. 03-0691, which gave an advance notice of a proposed change to rules that would allow movement
towards a "clean list" approach which would restrict entry of species not already known to be
safe.
Control efforts are largely regulated by individual states. Most states have some sort of
noxious weed list although in many states this list is more advisory than regulatory. In those in
which it is regulatory, the laws vary as to whether listing for control priorities also means
quarantining movement.
In Canada, the recent Invasive Alien Species Strategy for Canada was approved by
federal-provincial-territorial Ministers responsible for wildlife, forests, fisheries and aquaculture,
and endangered species in September 2004. It is anticipated that the draft action plans for various
invasive species, including terrestrial invasive plants, will be presented to Ministers for
consideration in September 2005. At present there is a Proposed Action Plan for Invasive Alien
Terrestrial Plants and Plant Pests.
Current regulations that address the invasive plant species problem are inconsistent
across jurisdictions. For example, differences exist between states as to the invasive species
programs being implemented as well as the species that are listed as invasive (Klein, 2004;
Mullin et al., 2000). The same is true in Canada, where some provinces have adopted noxious
weed listings but others have not (Myers and Bazely, 2003). The observed variation in policy is
problematic when considering that mail-order and internet sales are an important component of
the horticulture industry (Maki and Galatowitsch, 2004). Thus it is likely that plants originating
in one jurisdiction may be purchased in another, resulting in the transport across state or
provincial boundaries. If these states and provinces don’t share common policies, regulating this
type of trade will prove difficult.
In sum, many species that are considered invasive in the United States are also deemed
invasive in Canada, and vise versa. Therefore, it is reasonable to argue that there exists a need to
coordinate the control of invasive species from a regional perspective (Doelle, 2001), rather than
attending to the issue at a national scale. This is especially true within the context of the North
American Free Trade Agreement (Perrault et al., 2003). Therefore, the policy frameworks of
both countries need to be consistent in order to effectively manage the invasive plant species
problem.
5
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
3. Research Methods
3.i. Ecological and Economic Modeling of the Risk of Plant Invasion Establishment
As noted in the Introduction, two of the researchers involved in this proposal have begun
developing a cost-benefit framework to examine the commercial horticultural decisions to import
exotic plant species (Barbier and Knowler 2005; Knowler and Barbier 2005).
For example, the model developed by Barbier and Knowler (2005) indicates that the
number of plant-importing nurseries established is determined by the marginal profits of the last
nursery just equaling the expected social costs it generates through accidentally causing an
invasion in the region. The latter social costs have two components: the expected social damages
due to an increase in the rate of invasion over time (divided by an adjusted discount factor) and
the increase in expected damage cost per hectare caused by an additional nursery. This suggests
that any estimate of these benefits and costs associated with importing exotic plant species will
depend crucially on the following relationships: an expression for horticultural industry profits as
a function of the number of firms in the industry; the probability that a species is likely to
become invasive, as a function of its innate characteristics and those of the potential host
environment; and the changes and damages over time to a particular eco-zone area that is
invaded. Preliminary estimates of these costs and benefits were calculated for purple loosestrife
(Barbier and Knowler 2005) and salt cedar (Knowler and Barbier 2005).
However, these studies should be considered only a first step toward a more
comprehensive and integrated ecological-economic analysis, as they were hampered by poor and
incomplete data on the profits of the horticultural industry, on the key invasive characteristics of
different exotic plant species, and on the likely impacts on and vulnerability of key affected ecozones. In addition, rather than assessing the benefit costs associated with importing exotic plant
species to both Canada and the United States, the geographical focus was limited solely to the
latter country. This not only restricts unnecessarily the data available for analysis of horticultural
nursery profits as well as the risks of accidental invasion but also ignores the possible ecological
and economic linkages pose by the invasive plant problem across North America. As noted in
Section 2.ii, both the United States and Canada have similar plant-importing horticultural
industries, and both countries share common eco-zones that are at risk from the impacts of
invasion posed by the same exotic species.
To improve the ecology and economics of analyzing the risks of invasion from the
commercial decision of the nursery industry to import exotic species and to apply this analysis to
the horticultural industry of North America requires amassing and integrating several new data
sources: ecological data concerning the invasive characteristics of individual plants and the
probability of invasion (e.g. Reichard and Hamilton, 1997); eco-zone data for US and Canada on
the introduction and spread of individual species that have become invasive (e.g. Thompson et
al. (1987) for purple loosestrife (Lythrum salicaria), Zavaleta (2000) for saltcedar (Tamarix spp)
and Haber (1998 and 2002) generally for Canada); and economic data for the US and Canadian
horticulture industry from the 1998 US Census of Horticultural Specialties (USDA, 2000) and
the Annual Greenhouse, Sod and Nursery Survey of Canada (Statistics Canada 2004).
With a seed money grant from the Center for Invasive Plant Management (CIPM) for an
eighteen-month pilot project, the co-investigators of this proposal have joined together to begin
preliminary work on developing further the ecology and economic modelling of the commercial
decision of private nurseries in the US and Canada to sell exotic species and the accompanying
6
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
risk of accidental introduction and establishment of plant invasives. Our team of three
economists (Barbier, Burgess and Knowler) and one ecologist (Reichard) is spread over three
different institutions in North America: Simon Fraser University (Knowler), University of
Washington (Reichard) and University of Wyoming (Barbier and Burgess). The CIPM
funding began in May 2004, and the bulk of the seed grant money provided limited financing of
a post-doctoral research assistant (Burgess) to assist with research tasks. The remainder of the
CIPM funding enabled our team to have one initial meeting, in January 3-7 2005, to outline the
research required to develop and estimate improvements in our ecological-economic model of
horticultural industry profits and the risk of invasion, which has formed the basis of this PREISM
proposal.
3.ii. Research Tasks
Our proposed research of the ecological-economic modelling of the costs and benefits
associated with the possible accidental introduction and establishment of plant invasives through
commercial horticultural operations consists of the following inter-related tasks.
(1)
Modeling the economic behavior of a profit-maximizing horticultural industry that
imports an exotic plant species through establishing nurseries at specific geographical
locations in North America.
As part of our theoretical framework, we intend to develop a model of a private
commercial plant breeding industry operating under conditions of monopolistic competition that
imports an exotic plant species into a region by establishing nurseries at various locations. Our
previous economic analysis suggests that the North American horticultural operation satisfies
market conditions conforming to monopolistic competition (Barbier and Knowler 2005; Knowler
and Barbier 2005). For instance, the reason for restricted entry in the horticultural industry is that
there are a finite number of "prime" locations in most regions for establishing plant breeding
nurseries, due to the geographical distribution of consumers and input suppliers (i.e. distance to
markets) or to the variable quality of the land and other environmental conditions required by
nurseries. That is, the total profits of the industry are positive, but the marginal profit of the last
nursery established at the final location is zero.
A monopolistic competition model of the horticultural industry will enable us to
determine the aggregate level of profits of the entire horticultural industry as a function of the
total number of nurseries established in each unique location by the industry. This relationship
will become important when we compare the tradeoff between the profits made and the expected
social damages associated with the creation of additional nurseries by the horticultural industry.
Another important feature of developing a monopolistic competition model of the
horticultural industry is that such a model allows considerable flexibility in assessing possible
policy interventions. An important feature of economic models of monopolistic competition is
that they assume a one-to-one relationship between a firm (i.e. in our model, a nursery at a
specific location) and its differentiated share of the market (i.e. its level of sales for the local
market). It follows that any policy that regulates the “sales” of exotic plants by nurseries is
tantamount to regulating nurseries themselves, and equally, any policy that regulates the
“optimal number of nurseries” can easily translate into limiting nursery “sales”. This means that
we can consider policy interventions that control the number of nurseries established by the
horticultural industry, such as an “introducer’s pay” tax that internalizes the expected social cost
7
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
of an accidental invasion or a fixed quota on the number of new nurseries allowed, and also
determine the impact on total horticultural sales.
Our previous attempts to model the monopolistic competition features of the horticultural
industry used the “classical” model with U-shaped average cost curves (see, for example, Varian
1984, pp. 85-91). In the proposed research, we will model the monopolistically competitive
behavior of the horticultural industry using the Dixit-Stiglitz approach (Dixit and Stiglitz 1977).
This type of model is now standard in monopolistic competition models in economic geography
and international trade (see, for example, Baldwin et al. 2003; Fujita et al. 1999; Krugman 1979
and 1980; Neary 2001).
The Dixit-Stiglitz framework will confer two additional advantages over our previous
monopolistic competition model. First, the Dixit-Stiglitz framework models both consumer and
industry behavior in a monopolistic competitive market. This will facilitate our ability to assess
the welfare effects of any policy interventions in terms of impacts of both producer surplus and
consumer surplus effects. Second, as the economic geography literature has demonstrated, the
Dixit-Stiglitz framework is ideal for examining the location and trade effects of an industry that
operates over two regions, especially under conditions where there may be a significant policy
change in one region but not the other (see in particular Baldwin et al. 2003). This is directly
relevant to our analysis of possible policy interventions in North America to control the
accidental introduction of plant invasives by the horticultural industry, when for example one
“region” (e.g. Canada) decides to adopt a more stringent policy of controlling the number of
domestic nurseries or exotic plant sales than the other region (e.g. the US). One possible effect
of the lack of policy coordination between the two regions is that the Canadian horticultural
industry might relocate its nursery operations in the US but use internet and postal sales to “ship”
exotic seeds and plants back to Canadian customers. By applying the Dixit-Stiglitz framework
in a two-region model of the North American horticultural industry, we will be able to analyze
such policy consequences and its welfare impacts in the two regions.
We will also use the monopolistic competition model as the basis for estimating
horticultural industry profits as a function of the number of established nurseries. In a previous
analysis, Knowler and Barbier (2005) industry profits were specified as a quadratic function of
nurseries, and data only for the US horticultural industry by state from USDA were used to fit
the model (USDA, 2001). Using the new Dixit-Stiglitz modeling framework we anticipate
improving upon the specification of this econometric model. We also believe that we can
improve and extend the estimation for the entire North American horticultural industry by
utilizing economic data for the US and Canadian horticulture industry from more recent USDA
horticultural census data and the Annual Greenhouse, Sod and Nursery Survey of Canada (e.g.,
Statistics Canada 2004).
(2)
Ecological and economic analysis of the risk and potential damages of accidental
introduction and establishment associated with the commercial plant industry importing
and breeding exotic plant species at its various locations.
We next propose to model the expected social damages associated with the creation of
nurseries by the horticultural industry, which is the main purpose of this task and the following
one.
If an exotic plant introduced into a region through such commercial horticultural
operations escapes and becomes successfully established in the wider natural environment of the
8
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
host region, then the invader can cause extensive damages, e.g. through crowding out native
plant species essential to natural ecosystems, by infesting livestock ranges and cropland, through
changing the habitat of fauna in the area, by altering key ecosystem services (e.g. changing
nutrient cycles, hydrological conditions and enhancing fire cycles), through clogging waterways,
irrigation ditches and other water bodies, and by becoming a lawn and garden weed. In addition
to the economic costs of such damages caused by invasive species, both public authorities and
private individuals may incur considerable costs in controlling or limiting the spread of a plant
invasive. Thus, when an exotic plant is imported into a new region by a commercial horticultural
industry, there is a probability that the species may become an invasive, and as a result,
additional social costs will arise. We refer to this potential cost as the expected social cost of
invasion associated with a commercial plant breeding or nursery industry.
We plan to develop the economic analysis of the accidental risk of invasion associated
with the commercial plant industry importing and breeding exotic plant species at its various
locations. We believe that this problem has similarities to a standard duration problem, where
the “spell” represents the number of periods after introduction of the species without invasion
taking place. The risk that invasion will occur in a given period, given that it has not become
invasive yet, can be described by a hazard function. We postulate that the key determinants of
the hazard are the exogenous characteristics of the exotic plant itself, the vulnerability of the host
region to invasion and the number of commercial nurseries selling the exotic plant and thus
contributing to dispersal. The problem for the decision-maker is then to choose the optimal
number of nurseries that balances the trade offs between the profits of the commercial plant
breeding industry with the expected losses associated with the risk of accidental introduction. We
therefore plant to adapt a model suggested by Reed and Heras (1992) that is suited towards
utilizing a hazard-function approach that translates this stochastic dynamic optimization problem
into a deterministic analogue.
The relevance of such a modeling approach is that it implies that the government's
optimal choice of nurseries selling a potentially invasive exotic species in the long run will be
less than that of a competitive plant breeding industry. As a result, we will be able to consider the
possibility of employing regulatory or market-based instruments (e.g. standards versus taxes) to
ensure that the plant breeding industry internalizes the expected social cost of an accidental
invasion associated with establishing new nurseries. Of particular interest to this policy decision
is the relative influence of the hazard function on the expected marginal social costs of invasion
associated with horticultural operations. Since the hazard function acts as a premium on the
social discount rate, this serves to increase the size of the nursery industry as the hazard increases
(Clarke and Reed, 1994). This counterintuitive result stems from the well-known observation
that increasing risk leads to a desire to discount more heavily, thereby speeding up consumption.
Since invasion is inevitable in our model, it follows that the commercial nursery industry should
grow larger to take advantage of its commercial opportunities before the invasion takes place. In
contrast, the marginal hazard term should have the opposite effect – since more nurseries lead to
a greater risk of invasion, there is a penalty associated with a larger industry. Which effect
dominates, as the hazard changes, depends on the specification of the hazard function and its
magnitude.
Our next step in our ecological-economic analysis will therefore be to estimate the hazard
function for determining the probability that an imported exotic species will become established
as an invasive if it has not already become one to date.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Some of our previous work made a preliminary attempt at this analysis (Knowler and
Barbier 2005). In this work, we assumed that the hazard rate function is given by h(a; n), where
a represents species characteristics and n represents environmental factors That is, the hazard is
independent of duration but relies on several covariates, one of which is time-varying, n(t) the
number of horticultural operations, and the other is not, a the attributes of plants that make them
more or less susceptible to be established as invasives in host environments. To model the
influence of the covariates we used a proportional hazard model (Kiefer, 1988), which we
simplify so that the hazard function can be estimated using an ordered logit procedure suggested
by Han and Hausman (1990). The data on plant attributes used were from Dalsimer (2000), who
surveyed land managers who deal with invasive plants on a routine basis. She asked questions
about the biological characteristics of individual plants as well as local ecosystems vulnerable to
invasion; the resulting database contained 114 data points, which was sufficient for estimation
purposes. The dependent variable consisted of four categories of invasiveness: highly invasive
(T1), moderately invasive (T2), slightly invasive (T3), and not yet known to be invasive (T4).
We believe that we can improve considerably on this estimation of the hazard function by
incorporating better ecological data concerning the invasive characteristics of individual plants
and the probability of invasion (e.g. Rejmánek and Richardson 1996; Reichard 1997; Reichard
2001). These studies have documented that traits relating to high reproduction and stresstolerance and positively associated with successful invaders and negatively associated with noninvaders. Such traits include high seed production and viability, vegetative reproduction, and
nitrogen-fixation.
To complete our analysis of the expected social damages of any invasion associated with
a commercial plant breeding or nursery industry is we will need to estimate the potential
ecological and economic impacts on key eco-zones in the US and/or Canada that may be
affected. Previous work by Knowler and Barbier (2005) and Barbier and Knowler (2005)
employed a standard logistic growth function to describe the rate of spread of invasion over the
area of the host environment, as suggested by Shigesada and Kawasaki (1997). Solution of the
growth function enabled formulation of an expression for the present value of invasion damages
at the point of time in which an exotic plant species becomes successfully established in the host
environment.
In the proposed task, we plan to improve this analysis by collecting better eco-zone data
for US and Canada on the introduction and spread of individual species that have become
invasive (e.g. Thompson et al. (1987) for purple loosestrife (Lythrum salicaria), Zavaleta (2000)
for saltcedar (Tamarix spp) and Haber (1998 and 2002) generally for Canada).
(3)
Integrating these economic and ecological analyses to model the potential policy
tradeoff between the profits of the commercial plant breeding industry with the
expected losses associated with the risk of accidental introduction.
The next step in our methodology is to integrate the first two tasks into a single model to
enable us to provide analysis of specific case study simulations of the potential tradeoffs between
the commercial profits of the North American horticultural industry and any expected social
damages from potential risks of invasion.
To illustrate how such modeling simulation will be conducted, we will use the example
of the simulation conducted for salt cedar by Knowler and Barbier (2005) in previous research.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
For example, for salt cedar, Knowler and Barbier (2005) devised four different basic
models based on varying simplifying assumptions concerning the specification of a prototype
hazard function, f1(n), and the potential environmental damages of the invasive:
- Model (a): the non-linear specification for the influence of industry size on the hazard, f1(n),
together with the low estimate of the damages from invasion;
- Model (b): the linear specification for the influence of industry size on the hazard, f2(n),
together with the low estimate of the damages from invasion;
- Model (c): the non-linear specification for the influence of industry size on the hazard, f1(n),
together with the high estimate of the damages from invasion; and,
- Model (d): the linear specification for the influence of industry size on the hazard, f2(n),
together with the high estimate of the damages from invasion.
The results for salt cedar indicate that, in all four cases, the socially optimal number of
nurseries was lower than the long run private equilibrium, where no consideration is given to the
risk of invasion. However, it was clear that the marginal hazard has an important role, since there
were marked differences in the results using a non-linear hazard function in comparison to the
linear specification, i.e. Models (a) and (c) versus Models (b) and (d). In the former case, the
very small marginal hazard at larger sizes of the industry resulted in a relatively small effect
from the presence of a risk of invasion, evident in the minor deviations in the optimal size of the
industry from the private outcome. This observation held even when other modeling assumptions
were varied (e.g. size of invasion damages, share of industry profits, etc.), including assumptions
about the characteristics of the plant species, as captured by the hazard rate.
Examination of the results using a linear specification for the function, represented by
Models (b) and (d), confirm the above observation. The optimal number of nurseries selling the
exotic plant was more sensitive to model assumptions with a constant marginal hazard. For
example, when the hazard rate is high, no sales of the exotic plant species are desirable, while a
positive number of nurseries are permitted to sell the exotic if the hazard rate is low (except in
one case).
It is of course very difficult for us to predict what new “models” will emerge from our
proposed research in tasks (1) and (2) to develop an integrated ecological-economic analysis of
the tradeoffs between the commercial profits of the North American horticultural industry and
any expected social damages from potential risks of invasion. However, we do anticipate that
qualitatively the same general methodology will result. Once we have integrated the first three
research tasks into a single model, we should be able to analyze specific case study simulations
indicating the extent to which the optimal number of nurseries will differ from the long run
private equilibrium, where no consideration is given to the risk of invasion. Moreover, as the
above salt cedar example indicates, we also believe that our estimation of the hazard function is
likely to have an important bearing on the deviation between the social and private equilibrium
for the horticultural industry.
(4)
Evaluation of possible policy interventions for reducing the risk of accidental
introduction by the North American horticultural industry.
The model constructed in task (4) will enable us to assess numerous policy scenarios.
The principal ones that we have identified initially are:
a) do nothing
11
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
b) voluntary self regulation by the horticultural industry (codes of conduct, niche
market etc)
c) government interventions (e.g. taxing or banning the sale of exotic species or the
establishment of new nurseries)
d) policy coordination between US and Canada to regulate the cross-border trade in
exotic plant species.
We believe that our integrated ecological-economic model should provide important
insights into the costs and benefits of these various policy options. As an illustration, we again
use the example of the salt cedar analysis conducted by Knowler and Barbier (2005), which was
used to assess the implications of an “introducers pay” tax on nurseries to internalize the
potential risk of plant invasion.
The analysis by Knowler and Barbier (2005) showed that the values for the introducers
pay tax required to bring about the socially optimal size of the industry were primarily sensitive
to the profitability of the exotic plant species. However, there were dramatic differences in the
tax between models, and again these appear to result from differences in the marginal hazard
function.
More importantly, the results of Knowler and Barbier (2005) indicate that the mere
presence of a risk of invasion associated with an exotic plant species does not mean that it is
socially optimal to “ban” commercial sales of the species if it is valued by consumers as an
ornamental plant. For certain specifications of the hazard function, an introducers’ pay tax
becomes a very feasible policy instrument for ensuring that commercial horticultural operations
fully incorporate the expected social costs of an accidental plant invasive introduction.
4. Conclusion
The pilot grant from the Center for Invasive Plant Management (CIPM) Montana State
University enabled the three co-investigators to meet for a two-day workshop at the University of
Wyoming, during January 6-7, 2005, to discuss the state of ecological and economic modeling of
the risks of introduction of plant invasives through the commercial horticultural trade. This
preliminary meeting revealed that much work has been done independently to understand the
risk of invasive plant establishment through horticultural trade. As reported in this proposal, we
now feel that by combining the tools and data already available in both economics and ecology,
our interdisciplinary effort can present a clearer understanding of both how horticultural trade
fosters plant invasions and provide recommendations to guide mitigating this pathway.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Citations to Project Description
ATTRA, 1996. Purple loosestrife: Public enemy #1 on federal lands. ATTRA Interior Helper
1(2): 2.
Baldwin, Richard, Rikard Forslid, Philippe Martin, Gianmarco Ottaviano, and Frederic RobertNicoud 2003. Economic Geography and Public Policy; Princeton: Princeton University
Press.
Barbier, E.B. 2001. A note on the economics of biological invasions. Ecological Economics
39(2): 197--202.
Barbier, E.B. and Knowler, D. 2005. “Commercialization decisions and the economics of
introduction.” Euphytica, in press.
Barbier, E.B. and J.F. Shogren. 2004. “Growth with Endogenous Risk of Bioinvasion.”
Economic Inquiry 42(4):587-601.
Claudi, R. 2002. “Environmental and Economic Costs of Alien Invasive Species in Canada.”
Report by RNT Consulting Inc. for the Canadian Information System for the
Environment (CISE), Environment Canada, Quebec.
Dalsimer, A.A., 2000. Predicting the Spread of Non-indigenous Invasive Plant Species: Can it be
Done?. Georgetown Public Policy Institute, Washington, D.C. (thesis).
Dixit, A., and J.E. Stiglitz 1977. "Monopolistic Competition and Optimum Product Diversity."
American Economic Review 67: 297-308.
Doelle, M. 2001. Legal and Policy Responses to Invasive Species. Background Paper
Commission for Environmental Cooperation. Retrieved January 20, 2005, from
http://www.cec.org/files/PDF/BIODIVERSITY/Legal-Policy-ResponsesInvasivesSpecies_en.pdf
Eiswerth, M.E. and W.S. Johnson. 2003. “Managing Nonindigenous Invasive Species: Insights
from Dynamic Analysis.” Environmental and Resource Economics 23:319-342.
Fujita, M., Krugman, P. and Venebles, A. 1999. The Spatial Economy: Cities, Regions and
International Trade. The MIT Press, Cambridge, Massachusetts.
Haber, E. 1998. “Impact of Invasive Plants on Species Habitats at Risk in Canada.” National
Botanical Services. Prepared for the Canadian Wildlife Service, Environment Canada,
Ottawa.
Haber, E. 2002. “Invasive Species of Canada Survey 2002: An Assessment of Resources and
Needs.” National Botanical Services. Prepared for the Canadian Wildlife Service,
Environment Canada, Ottawa.
Han, A. and Hausman, J.A., 1990. Flexible parametric estimation of duration and competing risk
models. Journal of Applied Econometrics, 5:1-28.
Hirsch, S.A. and J.A. Leitch. 1996. The impact of knapweed on Montana's Economy. North
Dakota State University, Agricultural Experimental Station, Agricultural Economics
Report no. 355. 43 pages.
Jerardo, A. 2002. “Floriculture and Nursery Crops Outlook.” Electronic Outlook Report from the
Economic Research Service FLO-1, U.S. Department of Agriculture, Washington, DC.
Kiefer, N.M., 1988. Economic duration data and hazard functions. Journal of Economic
Literature, XXVI (June):646-679.
Klein, B. 2004. Making a list. prevention strategies for invasive plants in the Great Lake States.
Environmental Law Institute.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Knowler, D. and Barbier, E.B. 2005. “Importing exotic plants and the risk of invasion: are
market-based instruments adequate?” Ecological Economics 52:341-354.
Knowler, D. & E. Barbier, 2000. The economics of an invading species: a theoretical model and
case study application. In C.Perrings, M.Williamson, and S. Dalmazzone (Eds), The
Economics of Biological Invasions. Edward Elgar, U.K.
Krugman, Paul R. 1979. "Increasing Returns, Monopolistic Competition, and International
Trade." Journal of International Economics 9: 469-479.
Krugman, Paul R. 1980, "Scale Economies, Product Differentiation and the Pattern of Trade."
American Economic Review: 67, 298-307.
Maki, K., Galatowitsch, S. 2004. Movement of invasive aquatic plants into Minnesota (USA)
through horticultural trade. Biological Conservation 118: 389-396
Mullin, B.H., Anderson, L.W.J., DiTomaso, J.M., Eplee, R.E. and Getsinger, K.D. 2000. Council
for Agricultural Science and Technology CAST Issue Paper 13 (February):1-18.
Myers, J.H. and Bazely, D.R. 2003. Ecology and Control of Introduced Plants. Cambridge
University Press.
Naylor, R.L. 2000. The economics of alien species invasions. In H. Mooney & R. Hobbs
(Eds.), Invasive Species in a Changing World, pp. 241—259. Island Press, Washington
DC.
Neary, J.P. 2001. “Of Hype and Hyperbolas: Introducing the New Economic Geography.”
Journal of Economic Literature 39(June):536-561.
OTA. 1993. Harmful non-indigenous species in the United States. U.S. Congress, Office of
Technology Assessment, OTA-F-565. U.S. Government Printing Office: Washington,
D.C.
Perrault, A., Bennett, M., Burgiel, S., Delach, A., Muffett, C. 2003. Invasive Species,
Agriculture and Trade: Case Studies from the NAFTA Context. Discussion paper for the
Second North American Symposium on Assessing the Environmental Effects of Trade.
Commission for Environmental Cooperation.
Perrings, C., M. Williamson, E. Barbier, D. Delfino, S. Dalmazzone, J. Shogren, P. Simmons, &
A.Watkinson, 2002. Biological invasion risks and the public good: an economic
perspective. Conservation Ecology 6(1): 1. [online] Available at:
http://www.consecol.org/vol6/iss1/art1
Pimental, D. 1991. Handbook on Pest Management in Agriculture.Volumes 1,2, and 3. Boca
Raton, FL: CRC Press
Pimental, D., L. Lach, R. Zuniga, & D. Morrison, 2000. Environmental and economic costs of
nonindigenous species in the United States. Bioscience 50(1): 53--67.
Reichard, S. 1997. Preventing the introduction of invasive plants. In Luken, J. and J. Thieret,
eds. Assessment and management of plant invasions. New York: Springer-Verlag. pages
215-227.
Reichard, S.H. 2001. The search for patterns that enable invasion prediction. In Weed Risk
Assessment, eds R.H. Groves, F.D. Panetta & J.G. Virtue, CSIRO Publishing,
Melbourne, Australia. Pages 10-19.
Reichard, S.H. and Hamilton, C.W. 1997. Predicting invasions of woody plants introduced into
North America. Conservation Biology 11(1):193-203.
Reichard, S.H. and White, P. 2001. “Horticulture as a Pathway of Invasive Species Introductions
in the United States.” BioScience 51(2):103-113.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Rejmánek, M. and Richardson, D.M. (1996). What attributes make some plant species more
invasive? Ecology 77, 655-661.
Settle, C. and J.F. Shogren. 2002. “Modeling Native-Exotic Species in Yellowstone Lake.”
American Journal of Agricultural Economics 84(5):1323-1328.
Shigesada, N. and Kawasaki, K., 1997. Biological Invasions: Theory and Practice.
Oxford: Oxford University Press.
Statistics Canada. 2004. Annual Greenhouse, Sod and Nursery Survey 2003. Statistics Canada,
Ottawa, Ontario.
Thompson, D.Q., R.L. Stuckey & E.B. Thompson, 1987. Spread, impact, and control of purple
loosestrife (Lythrum salicaria) in North America Wetlands. Fish and Wildlife Research
2. US Dept of the Interior, Fish and Wildlife Service, Washington DC.
USDA, 2001. 1998 Census of Horticultural Specialties. U.S. Department of Agriculture:
Washington, D.C.
[http://www.nass.usda.gov/census/census97/horticulture/horticulture.html ]
Zavaleta, E. 2000. The economic value of controlling an invasive shrub. Ambio
29(8):462-467.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Collaborative Arrangements
The lead institution for the proposed project is the University of Wyoming, and the
project director will be Prof Edward Barbier of the Department of Economics and Finance of
the University of Wyoming. Professor Barbier will be assisted in the project by Dr. Joanne
Burgess and one graduate research assistant.
The two collaborating institutions in the project are the University of Washington and
Simon Fraser University. The co-investigator at the University of Washington is Prof Sarah
Reichard, who will be assisted by a graduate research assistant. The co-investigator at Simon
Fraser University is Prof Duncan Knowler, who will be assisted by a graduate research
assistant.
Collaborative links between these researchers and institutions have already been
established as the result of a seed money grant from the Center for Invasive Plant Management
(CIPM) for an eighteen-month pilot project to begin preliminary investigations of the economicecological modeling required to assess the commercial decision of private nurseries in the US
and Canada to sell exotic species and the accompanying risk of accidental introduction. The
CIPM funding enabled our team of researchers (Barbier, Burgess, Knowler and Reichard) to
have one meeting at the University of Wyoming, in January 6-7 2005, to outline the research
required to improve the ecological-economic model of horticultural industry profits and the risk
of invasion, to identify sources of ecological and economic data and to outline the key research
tasks and collaborative arrangements necessary for the research of this proposed project.
As noted in the Project Description, we have identified four research tasks to be
conducted during this project. We envision that the collaborative arrangements for each of these
research tasks will be as follows:
The proposed task (1), modeling the economic behavior of the North American
horticultural industry, will be conducted mainly by Barbier and researchers at the University of
Wyoming, in consultation with Knowler and Reichard.
The econometric modeling of the hazard function in proposed task (2), ecologicaleconomic assessment of the risk of introduction and potential damages from plant invasives, will
be conducted mainly by Knowler and researchers at Simon Fraser University. The necessary
ecological analysis of plant characteristics data for this estimation will be conducted by
Reichard and researchers at the University of Washington. Thus, considerable collaboration
between Knowler and Reichard will be necessary to integrate this critical ecological-economic
analysis of the proposed research, in consultation with Barbier. In addition, the estimates of
potential environmental and other damages in key eco-zones of North America will be conducted
through close collaboration of Barbier, Knowler and Reichard and their associated researchers.
The proposed task (3), integrating the economic and ecological analyses into a single
policy analysis model, will be conducted through collaboration of Barbier and Knowler, in
consultation with Reichard.
The proposed task (4), the evaluation of policy options, will be conducted through
collaboration of Barbier and Knowler in consultation with Reichard on the policy option
scenarios to be assessed.
To facilitate collaboration, we have included funding for two annual meetings of
researchers at the University of Wyoming in our project budget.
1
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Vitae and Publications List(s) = PI and co-investigators. 2 page CV & 5 year publications
list.
2
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Budget (Form ARS-455).
3
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Indirect Cost Rate Schedule –applicant’s federally negotiated audited rate.
4
Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Current and Pending Support
The lead institution, University of Wyoming, has a $4,950 seed-money grant from the
Center for Invasive Plant Management, Montana State University, for a pilot study, “The
Ecology and Economics of Commercialization When Plants Carry a Risk of Becoming
Invasive”. The pilot project began in May 2004 and will end in September 2005. The CIPM
funding enabled our team of researchers (Barbier, Burgess, Knowler and Reichard) to have
one meeting at the University of Wyoming, in January 6-7 2005, to outline the research required
to improve the ecological-economic model of horticultural industry profits and the risk of
invasion, to identify sources of ecological and economic data and to outline the key research
tasks and collaborative arrangements necessary for the research of this proposed project.
Professor Knowler has obtained a one-year Canadian SSHRC scholarship over 2005/6
for a Master’s student, Ms. Arianne Ransoom-Hodges, to assist him in conducting research on
the plant invasive problem in North America and the current policies of the US and Canadian
governments to manage this problem. The SSHRC scholarship ends in May 2006.
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Prof. Barbier, University of Wyoming,
Practical Decision Analysis for Invasive Species Management
Additions to Project Description: reprints
Knowler, D. and Barbier, E.B., 2005, “Importing Exotic Plants and the Risk of Invasion: Are MarketBased Instruments Adequate?” Ecological Economics 52:341-354.
Knowler, D., 2005, “Reassessing the Costs of Biological Invasion: Mnemiopsis leidyi in the Black Sea,”
Ecological Economics, 52:187-199.
Barbier, E.B. and Shogren, J.R. 2004. "Growth With Endogenous Risk of Biological Invasion." Economic
Inquiry 42(4):587-601.
Barbier, E.B., 2001, "A Note on the Economics of Biological Invasions," Ecological Economics, 39(197202.
Reichard, S.H. and White, P., 2001, “Horticulture as a Pathway of Invasive Plant Introductions in the
United States,” 51(2):103-113.
Reichard, S.H. and Hamilton, C.W., 1997, “Predicting Invasions of Woody Plants Introduced into North
America,” Conservation Biology, 11(1):193-203.
6