Monday, June 30, 2008

Invasive Plant Research and Partnership

This is the report from a gathering of organizations and stakeholders which I helped bring together in March of 2008.
I wish to thank Dr. Phyllis Johnson, USDA ARS, retired, for coming up with the idea of a meeting of the minds, and Dr. Chris Dionigi, NISC, for making this meeting possible.
Invasive Plant Research and Partnerships with Ornamental Horticulture and Natural Resource Management Workshop Report

Sponsored by:
U. S. National Arboretum
Beltsville Agricultural Research Center
The Nature Conservancy
The American Nursery and Landscape Association
National Invasive Species Council

Suggested Citation: Invasive Plant Research and Partnerships with Ornamental Horticulture and Natural Resource Management Workshop Report. May 2008. Workshop sponsored by U. S. National Arboretum, USDA Beltsville Agricultural Research Center, The Nature Conservancy, The American Nursery and Landscape Association, National Invasive Species Council, and Invasive Species Advisory Committee. Held March 3 and 4, 2008, at the U.S. National Arboretum, Washington, D.C. 30pp.
Executive Summary…………………………………………… 3
1. Introduction………………………………………………… 6
2. General Consensus Points…………………………………. 7
3. Research Prioritization Criteria and Planning…………… 8
4. Research Focus Areas………………………………………. 9
5. General Strategic Research Planning Needs……………… 10
6. Process and Institutional Recommendations……………… 11

7. Issues Outside the Scope of the Workshop……………….. 12

Appendix 1: Workshop Participants………………………… 13

Appendix 2: Meeting Agenda………………………………… 17

Appendix 3: Invasive Species Definition Clarification…...… 18

Appendix 4: On-line Resources……………………………… 30

Executive Summary
Many non-native plants are important components of gardens, farms, orchards, and landscapes. However, some non-native plants escape cultivation and cause economic and environmental harm. These “invasive plants[1]” complicate efforts to sustain our natural areas and cultivated landscapes. The environmental conservation community, federal resource managers, the horticulture industry, and others all seek to avoid the introduction and spread of invasive plants. Development of new plant cultivars that retain valuable horticultural characteristics and also exhibit “non-invasive” attributes, e.g., sterility, provide enhanced planting options and reduce the likelihood of undesired spread. However, the degree that traits are exhibited by plants can vary among cultivars, and there are no agreed upon scientifically demonstrable standards for “sterile,” “hardy,” and “non-invasive” traits. In addition, plants and their environments are dynamic. Rising carbon dioxide concentrations, atmospheric deposition of nitrogen, habitat fragmentation, and other global-scale processes impact plant invasions within the decadal periods envisioned by current landscape and natural resource management plans.

On March 3 and 4, 2008, a workshop was held at the U.S. National Arboretum. Representatives of the horticulture industry, natural resource managers, environmental conservation groups, researchers, and others identified strategic knowledge gaps and priorities for ornamental plant breeding and natural area protection research and related issues. The focus was on the USDA’s U.S. National Arboretum’s and the Beltsville Agricultural Research Center (BARC) research agendas. Research by other agencies and institutions was also discussed.
General Consensus Points:
1) Industry and natural resource conservation stakeholder groups represented were in consensus concerning the importance of coordination and avoiding the introduction and spread of invasive plants.

2) Partnerships and communication among industry representatives, natural resource managers, and research administrators are critical to the success of research programs.

3) Terminology can contribute to confusion. It is important to clarify terms initially, e.g., “invasive species,” during discussions.

4) Stakeholders, i.e., the horticulture industry and conservation groups, have not agreed upon standards (i.e., adequate levels of expression) for attributes such as “sterility,” and “non-invasiveness” in plant selections and cultivars. However, the relative effectiveness of the underlying genetic and/or physiological mechanisms that produce sterility in a cultivar provides a level of assurance of that cultivar’s anticipated performance in the field.

5) Decisions concerning codes of conduct, regulations, and planting recommendations should be based on “sound science.” Although specific scientific standards were not identified in this workshop, examples of the application of sound science principles were provided.

6) Systematics[2] is a critical limiting factor. There are critical shortages of trained systematics experts and gaps in the U.S. systematics research and collections infrastructure. For example, currently there is no comprehensive inventory of the cultivated plants in North America[3].

7) A critical limiting factor is shared access to reliable information. There is no centralized, searchable data source of credible, geographically-referenced information on the behavior of species, cultivars, and hybrids of cultivated plants in the field, i.e., information concerning their undesired spread, if any. Data exists in dispersed sources. Their reliability is difficult to determine and coverage is incomplete.

8) Finding solutions to complex problems requires research efforts at that are sustained over long periods at levels that are commensurate with the value of the resources a stake. Resources are a critical limitation.

Priority should be given to research projects that are:
1) Integrated - Establish or enhance strategic multi-sector partnerships that consider the integrated needs of a full range of stakeholders, such as conservationists, industry, and consumers;
2) Strategic - Build strategic “infrastructure elements,” avoid duplication, and employ the most efficient and up-to-date methodologies and approaches;
3) Important - Address urgent problems and/or problems where research would contribute to substantial positive economic and environmental benefits, and of;
4) Broad Application – Provide a sustained stream of new products and solutions that meet stakeholder and consumer needs in applications that range from highly cultivated landscapes to natural areas.
Research Focus Areas:
1) Non-invasive Alternatives:
a. enhanced techniques for reducing plant reproduction/spread, such as obligate (true)
sterility and lack of spontaneous vegetative reproduction, including specific gene and
chromosome (ploidy) manipulation;
b. enhanced methods for the scientific evaluation of new plants for invasiveness
(screening); and
c. develop scientific standards for non-invasive attributes, e.g., sterility.

Research Focus Areas Cont.:
2) Quantifying Harm/Benefits and Avoiding Negative Impacts:
a. determine the impacts (if any) of native plant cultivars on indigenous native plant
b. develop methods for objectively evaluating the harm/benefits of invasive plants on
native plant and animal populations and ecosystem services, such as effects on water
quality and wildlife habitat;
c. develop scientific methods for the evaluation of post-cultivation persistence/spread of
species, cultivars, and hybrids of cultivated plants;
d. determine how site-specific factors (i.e. soils, climate, and disturbance) influence plant
behavior in the environment and the harm/benefit caused by cultivars;
e. determine how(if) gene flow and pathogens influence plants’ invasiveness and impacts;
f. develop scientific objective methods for estimating (ranking) the invasive potential of
cultivars and hybrids of cultivated plants;
g. enhance methods for the detection, evaluation, and response to new invasions
(Early Detection and Rapid Response, i.e., EDRR); and
h. develop ways to identify invasive taxa (e.g. genetic markers) for use by field
personnel when evaluating plants found at sites.
1. Introduction
Many non-native plants are important components of gardens, farms, orchards, and landscapes. However, some non-native plants escape cultivation, spread, persist, exclude other species, and cause other forms of economic and environmental harm. Other plants arrive unintentionally as hitchhikers on materials, equipment, and by other pathways of introduction. These invasive plants[4] are harmful to natural areas and cultivated landscapes. They are ongoing problems for conservationists, gardeners, and public-sector resource managers. They complicate the shared challenge of sustaining our natural areas and cultivated landscapes. It can be difficult to correctly identify plants, especially closely related taxa in the field. Cultivars may not be readily discernible, even by experts. Additionally, certain hybrids can exhibit invasive characteristics that are not known in parent populations. The public, the environmental conservation community, and the horticulture and landscaping industry all seek to avoid the introduction and spread of invasive plants and protect both natural areas and cultivated landscapes.

Invasive species cross jurisdictional boundaries and require a coordinated multi-sector response. Executive Order 13112 created the National Invasive Species Council (NISC) to coordinate federal invasive species actions. NISC is co-chaired by the Secretaries of the Interior, Agriculture, and Commerce and in total contains thirteen members. The Invasive Species Advisory Committee (ISAC) is chartered under the Federal Advisory Committee Act to provide non-federal stakeholder advice to NISC. The coordination of research is an important aspect of NISC’s work, and critical to solving invasive species problems. Scientific information is also needed to provide a sound underpinning for self-regulation of invasive plants and for federal or state regulations.
Research is advancing our capacity to address invasive species issues. However, significant technical challenges and knowledge gaps remain. Currently, there is no comprehensive inventory of the plants in cultivation in North America. Many plant characteristics that contribute to “invasiveness” have been identified, but the underlying genetic, physiological, and ecological processes and interactions are poorly understood. Both plants and their environments are dynamic. The potential impacts of global-scale processes, particularly rising atmospheric carbon dioxide concentrations and nitrogen deposition, increase the invasiveness of some plants. These dynamics are increasingly a factor in invasive species policy and management decisions.
Scientific advances in molecular genetics, plant breeding, systematics, ecology, and other fields offer great promise and are very active areas of research. The development of new plant cultivars that retain valuable horticultural characteristics and also exhibit important “non-invasive” traits, such as stable sterility and a lack of spontaneous vegetative reproduction, provide enhanced options for new and replacement plantings, while reducing the likelihood of escape from cultivation. However, there are no agreed upon scientifically demonstrable standards for traits such as “sterile,” “hardy,” “non-invasive,” and “non-persistent” that would provide performance targets for plant breeding research and cultivar selection and evaluation efforts.

The U. S. National Arboretum maintains a 446 acre facility in Washington, DC that welcomes over 500,000 visitors a year. Additionally, the National Arboretum conducts nearly two-thirds of all the USDA-ARS’s research in ornamental horticulture. This $12.8 million per year research and education facility has made over 675 official ornamental/horticultural plant releases. The National Arboretum is part of USDA’s Agricultural Research Service’s Beltsville Agricultural Research Center (BARC). The nearby 6900-acre BARC research facility is the largest agricultural research facility in the U.S. The National Arboretum and BARC are uniquely qualified to provide scientific information that is needed to solve many of the problems concerning the invasiveness of ornamental plants.

On March 3 and 4, 2008, U. S. National Arboretum, BARC, The Nature Conservancy, The American Nursery and Landscape Association, Invasive Species Advisory Committee (ISAC) and NISC sponsored a workshop at the U.S. National Arboretum in Washington DC. A total of thirty-five representatives of the commercial horticulture industry, ISAC, natural resource managers, NISC, state government officials, environmental conservation groups, researchers, and other constituencies from across the U.S participated (see Appendix 1). Participants included: Dr. Peter Raven the President of the Missouri Botanical Garden and a Trustee of the National Geographic Society, Deputy Assistant Secretary of the Interior Paul Hoffman, and the Executive Director of NISC, Lori Williams. Facilitators were provided by the Department of the Interior and NISC.

Purpose and Scope of the Workshop:
This workshop was convened to explore whether a consensus could be reached among representatives of the commercial horticulture industry, natural resource managers, environmental conservation groups, and researchers concerning knowledge gaps and research priorities for ornamental plant breeding and testing and natural area protection. An emphasis was placed on discussion rather than formal presentations (see Appendix 2). Objectives were to identify specific focus research areas and criteria for prioritization of projects. The focus was on BARC and the U.S. National Arboretum’s research agendas. However, other research partner organizations were included and recommendations outside the scope of this meeting were also offered.

2. General Consensus Points
Participants represented a diverse range of stakeholders, interest groups, subject discipline areas, sectors, and regions. However, consensus was reached on several issues.

Participants agreed that invasive species are critical problems for both highly cultivated landscapes and for natural-resource conservation. The need for federal interdepartmental coordination and for input from the full range of stakeholders was identified as critical to the shared goal of avoiding the introduction and spread of invasive plants. Stakeholders have important resources and expertise, and they can provide specialized opportunities to test new methods and cultivars. However, no single agency or group can provide all of the perspectives and resources needed. Partnerships and communication among industry, natural-resource conservation, and research institutions were indentified as critical to the success of research programs. Invasive-species research requires new partnerships with institutions and constituencies in addition to those with long records of involvement with the USDA.

A key factor contributing to inefficient communication is “terminology.” What is meant by terms such as “sterile, hardy, non-invasive, weedy, and invasive species” varies among individuals. Some terms such as, “invasive species,” “variety” and “noxious” have definitions that are established Executive Order 13112, the Plant Variety Protection Act, and the Plant Protection Act. Additionally, supportive information concerning the definition of “invasive species” has been developed by ISAC (see Appendix 3). Certain definitions are appropriate for regulations others maybe appropriate for public information and educational campaigns. The use of definitions without explanation and clarification can lead to confusion and unintended interpretations of statements, documents and meeting outcomes. Participants agreed that it is important to clarify terms used during discussions and recognize the potential for miscommunication.

Development of new plant cultivars that retain valuable horticultural characteristics and also exhibit important “non-invasive” attributes, such as stable sexual sterility and lack of spontaneous vegetative reproduction, provide enhanced options for new and replacement plantings, while reducing the likelihood of escape from cultivation and undesired spread. However, the degree and stability (i.e. robustness) of those traits can vary among cultivars, over time and across regions. Various genetic and/or physiological mechanisms lead to different degrees of sterility. Stakeholders, such as the horticulture industry and conservation groups, have not agreed upon standards (i.e., adequate levels of expression) for attributes such as “sterility,” and “non-invasiveness” in plant selections and cultivars. However, the relative strength and stability of the underlying genetic mechanism(s) used to produce a trait provides an indication of a cultivar’s anticipated performance in the field. For example, cultivars that have reinforcing (redundant) mechanisms of sterility exhibit more robust sterility. Enhanced methods for the scientific evaluation of new plants for invasiveness (i.e., screening) would augment the field evaluation of plant selections.
Participants agreed that decisions concerning development of codes of conduct, regulations, and planting recommendations should be based on “sound science.” Although specific scientific standards were not determined in this workshop, examples of the application of sound science principles were provided, e.g., the California Horticultural Invasive Prevention partnership (CAL-HIP) project concerning Pampasgrass and Jubatagrass [Pampasgrass and Jubatagrass Threaten California Coastal Habitats. 1999. J. M. DiTomaso, E. Healy, C. E. Bell, J. Drewitz, and A. Tschohl, Leaflet #99-1. See Appendix 4].
A critical limiting factor is authoritative identifications of plant specimens and related systematics information. Currently, there is no single source of systematic information that researchers and others can use to find what cultivars are currently or have been grown in North America. Work toward a comprehensive cultivated flora of North America was presented. This flora will be very large and require on-going revision. It may use a “Wiki-type” open review and editing structure. A comprehensive cultivated flora would have several applications. For example, to obtain a Certificate of Protection under the Plant Variety Protection Act, plant breeders must demonstrate that a proposed new plant variety is “new and distinct” from all other varieties. Specifically, a cultivated flora would help plant breeders protect a new “non-invasive cultivar” by indicating what other varieties are in cultivation. Research advances could help plant breeders differentiate non-invasive cultivars from others by demonstrating the removal or suppression of the invasive traits. Additionally, the performance of a particular cultivar in the field, such as its spread, viable seed production, vegetative reproduction, hybridization, and other characteristics related to invasiveness could be entered into the database and be subject to review and revision. Currently, there is no centralized searchable data source of credible, geographically referenced information concerning the performance of cultivars. Information, such as undesired spread or persistence, may be available from dispersed sources. However, information about specific cultivars is often lacking, and the reliability of available data is difficult to determine.

Some cultivars may not be readily discernible, even by experts. There is a critical shortage of trained systematics experts. In the past, programs such as the National Science Foundation’s Partnerships for Enhancing Expertise in Taxonomy (PEET) provided support for the training of systematics and systematics research. However, new faculty positions, graduate fellowships, and research support for systematics are declining. Systematics laboratories and collections are also in decline. There is a need for enhanced methods to identify invasive taxa (e.g. genetic markers) that can be used by field personnel and others.

Finding solutions to complex problems requires sustained research that maintains the continuity of programs over time and is coordinated among locations and across subject discipline areas. Lapse in research support can undermine years of effort. Additionally, research funding should be at levels that are commensurate with the size of the resources at stake. The nursery industry is estimated to be about a $4.65 Billion industry (U.S. Department of Agriculture, National Agricultural Statistics Service page 9.) In 2005, U.S. grower sales receipts for annual and perennial bedding and gardening plants alone totaled about $2.6 billion (Floriculture and Nursery Crops Yearbook. Market and Trade Economics Division, Economic Research Service, U.S. Department of Agriculture, June 2006, FLO-2006.). Sustained support for research at levels that are commensurate with stakeholder needs was identified as critical gap.

3. Research Prioritization Criteria and Planning
Participants suggested several criteria for prioritizing research projects and suggestions for planning research.
Criteria for establishing priorities:
1. A priority should be placed upon research that not only solves a specific problem but also increases overall research capacities.
2. Certain projects exploit similarities among taxa and allow the rapid propagation of technical advances to other areas of application. Others offer a sustainable source of new products and other advances over time. Projects that offer broad and/or sustained applications should be given priority.
3. Certain problems are urgent. Research can expedite the detection of emerging problems and increase our ability to respond quickly while problems are localized and by that prevent more extensive harm. Priority should then be given to projects that increase our abilities to proactively avoid problems and take timely action.
4. Certain problems result in large economic costs and/or environmental impacts and research may provide large benefits compared to investments of time and research costs. Projects with a potential for extensive benefits should be given priority.
5. Advances in molecular genetics, plant breeding, systematics, and other fields may expedite research, and also make possible new solutions. Efforts that utilize “cutting edge” methodologies and advance the overall technical capacity should be given priority.
6. Research efforts that augment and complement other efforts but not duplicate them should be given priority.
Suggestions for planning research:
1. In addition to cultivated landscapes, planning should consider a range of potential applications, such as how specific research might be integrated with environmental restoration projects, biomass and bio-fuels production, overseas development programs, and natural area management.
2. The potential impact and relevancy of research should be considered so that there is a balance between long-standing problems and emerging “new” issues. Additionally, a balance between economic and ecological benefits should be sought.
3. Focus should be on researchable targets where it is anticipated that significant advances will be available within a five to twenty-year period. Timeline planning should anticipate partnerships needed to transfer basic research advances to the private sector for further development. The needs of consumers and those that supply consumer needs should be considered early in the planning process.
4. No single agency or group can provide all of the perspectives and resources needed. A project’s potential to establish and foster strategic partnerships should be evaluated.

5. Integrated planning should focus on enhancing overall capacities and infrastructure. Areas of strength, unique capacities, specific resources, roles and responsibilities within partnerships, and strategic gaps should be identified and then evaluated among research cooperators.
4. Research Focus Areas
Participants identified two focus areas for research. In addition, specific examples of research topics were suggested within the two focus areas.

1) The development of non-invasive cultivars that serve as alternatives to currently available invasive plants.

The development of enhanced techniques for manipulating plant reproduction/spread was identified as a way to develop new plant cultivars that retain valuable horticultural characteristics and also exhibit important “non-invasive” attributes. The manipulation of genes involved in sexual and vegetative reproduction, alteration of chromosome (ploidy) number, production of single sex populations and sterile hybrids were identified as approaches to developing obligate (true) sterility. Molecular techniques such as “knockout genes” and “epigenetics” or gene silencing may also be useful.

It is important to note that asexual and vegetative mechanisms can be important means of reproduction and spread. All mechanisms of reproduction and spread must be identified and addressed. Physiological and genetic information is needed to develop relative rankings of the invasive potential for cultivars and the scientific evaluation of new plants species and cultivars.

Gene flow or introgression of genes within populations could result in a reversion of the progeny of some plants to invasiveness. Cultivars that have very stable and/or reinforcing (redundant) mechanisms of sterility (and lack spontaneous vegetative reproduction) typically exhibit greater levels of sterility, and are less likely to regain an ability to reproduce than other cultivars. The type(s) of sterility bred into plant selections yielding new cultivars could be indicated at points of sale to facilitate purchaser choice.

2) Improved quantification and prediction of the current and potential harm and/or benefit of species and cultivars and avoiding negative impacts.

There is a need for improved methods to determine the benefits and harm (if any) caused by non-native plant cultivars and their underlying genetic, physiological, and ecological mechanisms. For example, various cultivars may harbor or inhibit pathogens or differ in their value as wildlife food. They may provide differing levels of ecosystem services, such as preventing soil erosion. The competiveness of cultivars with native plants may also vary among cultivars and across environmental gradients. In addition to the plants themselves, the potential for gene flow from cultivars of native species to indigenous (or local) native populations could impact plant and animal communities. Understanding of the underlying genetic, physiological, and ecological mechanisms that produce specific benefits or undesirable traits would guide further development of plant selections and evaluation of cultivars.

Interactions with physical conditions and the “human environment” can be critical to a cultivar’s performance. Cultivars may differ in their responses to soils, fire, flooding, precipitation, climate change, light quality and quantity, and both natural and human-induced disturbance. The need for objective quantitative methods to determine “invasiveness” e.g., post-cultivation persistence, spread, and harm (if any) of cultivars across environmental gradients and a range of environmental applications is needed.

The combination of early detection, rapid assessment, and rapid response (EDRR) can prevent larger negative impacts from invasive species. Improved GIS-based methods for finding invasive populations that are large enough to detect, but localized enough to contain and eradicate are needed. Systematic analysis and access to up-to-date and accurate inventory and mapping data are needed for the timely assessment of suspected invasions and prediction of spread and impacts. Improved methods for the containment and eradication of localized invasive species populations are also needed.

5. General Strategic Research Planning Needs
Central to strategic planning is the clear identification and articulation the actual or “root” problem to be solved by the research. Focus should remain on what objective is actually to be accomplished and differentiate between objectives and strategies towards an objective. For example, is the objective to remove invasive populations or it is to reduce their impacts? Is it to promote the recovery of native species or maintain ecosystem services? Is the prevention of invasive species range expansions the objective or a strategy towards a larger objective? Seemingly subtle differences can lead to very different outcomes. Research recommendations should identify priority problems rather than “desired” or predetermined solutions. This allows researchers to bring the latest advances and strategies to bear on problems and allow for unanticipated or “creative” solutions, rather than trying to achieve a specific solution. Close coordination with research partners and on-going stakeholder review helps ensure that research remains directed at core problems.

Many ornamental plants are long-lived species and are planted across wide regions. Research planning should consider large-scale and long-term factors, such as climate change, habitat fragmentation, and changes in land use. To facilitate this, there is a need for global climate modeling as related to invasive species threats and interactions. Information, such as current and potential ranges, rates of spread, and predicted effects of increased nitrogen and carbon dioxide availability could guide research efforts. Additionally, information on plant systematics and mapping, cultivar sterility, persistence, growth, and spread within and among regions, vegetative growth and interactions with native plant populations, and plant and site-specific factors that contribute to invasiveness is needed. In some cases, invasive species may be symptomatic of both global-scale processes and localized disturbances. These underlying factors must be addressed to achieve invasive species objectives.

6. Process and Institutional Recommendations
Adoption of products and practices depends in part upon consumer choice. A better understanding of consumer attitudes towards invasive species, why and how they make planting choices, and how best to market alternatives can help guide research. Enhanced agency information staff participation is needed in research planning rather than just “after the fact.”
Scientifically-sound reinforcing messages must be provided to consumers directly and by those that they rely upon for information. “Awareness messages” should be coupled with “action” or “what I can do” messages. Information and technology transfer staff members can facilitate the transfer of research results to professional educators, Master Gardeners, horticulture and landscape professionals, and Land Grant University personnel. However, in addition to these “traditional contacts,” information staff members should develop contacts with conservation organizations and other stakeholders so that they are aware of ARS-generated developments.

Academics have access to scientific publications in peer-reviewed journals and presentations at scientific society meetings. These communicate effectively within the academic community, but they are not sufficient for consumer education needs. Communicating research findings to consumers is also required.

Much of the information produced is supported by federally agencies or grants. These data are in the public domain. There are extensive data sources, such as the USDA’s Natural Resource Conservation Service’s PLANTS database and those at the USDA’s National Agricultural Library. However, there is no centralized repository of searchable geographically-linked data. Data are available from dispersed sources, but reliability of those data is difficult to determine. Although data are often lacking, conducting a comprehensive analysis of gaps is also difficult.

Interdepartmental and interagency review of research contributes to improved quality assurance of the products and practices developed. Cross-agency coordination with Department of the Interior, Animal Plant Health Inspection Service, and other agencies increases ARS’s service to those action agencies and departments.

Research, especially with long-lived plant species, may require long timeframes and have both a high risk of failure and a high impact. The evaluation and compensation of researchers involved in “high risk” and long-term research needs to differ from that used to evaluate researchers involved in shorter-cycle projects.

7. Issues Outside the Scope of the Workshop
Research questions concerning biofuel crops, forage crops, and large-scale post-fire restoration plantings were identified as being similar to those discussed at this workshop that was focused upon ornamental plants. In addition, determining the most effective forms and methods for public communication of important invasive-species concepts, e.g., what is an invasive species and what actions should an individual take, were identified as important to the overall success of programs.
Appendix 1: Workshop Participants
Present at the Workshop:
Elenor Altman Adkins Arboretum
Gordon Brown U.S. Department of the Interior
Chip Cameron Facilitator
Steve Clemants Brooklyn Botanic Gardens
Brian E. Corr Ball Horticultural Company
Hilda Diaz-Soltero U.S. Department of Agriculture
Chris Dionigi NISC Staff
Thomas Elias USDA U.S. National Arboretum
Amy Frankmann Michigan Nursery and Landscape Association and ISAC
Dave Fujino California Center for Urban Horticulture
Susan Goodwin Facilitator
Robert Griesbach USDA Agricultural Research Service
John Hammond USDA U.S. National Arboretum
Nadine Hiers USDA U.S. National Arboretum
Paul Hoffman U.S. Department of the Interior
Carol Holko Maryland Department of Agriculture
Kate Howe The Nature Conservancy
Gary Knosher Midwest Groundcovers, LLC
Faith Kuehn Delaware, Plant Protection and Weed Management Section
Kerrie Kyde Maryland Department of Natural Resources
Wayne Mezitt Weston Nurseries
Richard Olsen USDA U.S. National Arboretum
Margaret Pooler USDA U.S. National Arboretum
John Randall The Nature Conservancy
Tom Ranney North Carolina State University
Peter Raven Missouri Botanical Garden
Craig Regelbrugge American Nursery & Landscape Association
Robert E. Schutzki Michigan State University
Joe Spence USDA Animal Health Inspection Service
Carol Spurrier U.S. Bureau of Land Management
Catherine Hazlewood The Nature Conservancy and ISAC
Marc Teffeau American Nursery & Landscape Association
John Peter Thompson The Behnke Nurseries Company and ISAC
Mary Travaglini The Nature Conservancy
Lee Van Wychen Weed Science Societies of America
Valerie Vartanian The Nature Conservancy
Alan Whittemore USDA U.S. National Arboretum
Mark Widrlechner USDA North Central Regional Plant Introduction Station
Lori Williams NISC Staff
Lewis Ziska USDA Agricultural Research Service

Appendix 2:
Workshop on Invasive Plant Research and Partnerships with Ornamental Horticulture and Natural Resource Management

Monday, March 3, Objective – Discuss and identify the issues
Discussion Lead
8:30 - 9:00
Arrive & sign in

9:00 - 9:10
Welcome from National Arboretum

National Arboretum: T. Elias
9:10 - 10:00
- Introductions around the table
- Groundrules
- Agenda review

10:00 - 10:50
Overview of work on Invasive Species
- National Invasive Species Council (NISC)
- Invasive Species Advisory Committee (ISAC)
- USDA: Agricultural Research Service (ARS)
- Questions & comments
NISC: P. Hoffman
NISC/ISAC: L. Williams
ARS: J. Spence

10:50 - 11:10

11:10 - 11:50
How will outcomes of meeting be used?
- Research priorities & national program planning
- Transfer of technology & research results to industry & resource managers
- Questions & comments
ARS National Program Staff: G. Wisler
Office of Technology Transfer: R. Griesbach

Monday, March 3, Cont.
11:50 - 1:00

1:00 - 3:00
Panel Discussion:
- Background & importance of issue from perspectives of industry, conservation community, & Federal government
- Questions & comments
ANLA: M. Teffeau C.Regelbrugge
TNC: J. Randall V. Vartanian
Federal: H. Diaz-Soltero, G. Brown
3:00 - 3:15

3:15 - 3:45
Climate Change & Cultivars
- Climate change impacts on planting & resources management decisions
- Questions & comments
BARC: L. Ziska
3:45 - 4:15
Systematics – What plants are here now?
- What do we know & need to know about cultivated plants in North America
- Questions & comments
Missouri Botanical: P. Raven
4:15 - 4:30
Wrap up & prepare for second day
- Overnight assignments? Things to think about?
- Plus/Delta (what went well today & what should we change for tomorrow)

Tuesday, March 4, 2008, Objective – Identify researchable targets
Discussion Lead
8:30 - 9:00
Arrive & check in

9:00 - 9:30
Recap from Day 1 & Agenda overview of Day 2
9:30 - 10:30
What abilities do we have now? In the next 5-10 years?
- Current systematics, bredding & selection programs & methods
- Emerging technologies, new methods & opportunities, e.g. genetic sterility.
- Questions & comments
ARS: R. Olsen

10:30 - 10:45

10:45 - 11:45
Small Group Discussions- Develop initial list of Researchable Targets (problems to be solved)
- Criteria for prioritizing targets (e.g. costs/impacts/importance of the problem, technical feasibility of solutions, strategic partnerships availability, duplication avoidance (is it already being done?), & etc.)
Each group will identify a facilitator & recorder
11:45 - 12:15
Small groups report back to full group
Facilitators will record on flip charts
12:15 - 1:15

1:15 - 3:30
Identify Priority Researchable Targets: Link priority problems & potential approaches/opportunities.
- Criteria for identifying & prioritizing researchable targets
-Application of criteria to researchable targets
- Identify potential candidate targets
- Identify resource gaps, barriers and opportunities to complete target research & strategize about how to fill gaps (ie. leveraging resources through partnerships, other opportunities…)

Full group discussion
3:30 - 4:15
Identify roles, timetable & next steps
4:15 - 4:30
Wrap up & Plus/Delta

Appendix 3: Invasive Species Definition Clarification and Guidance White Paper

Invasive Species Definition Clarification and Guidance White Paper
Submitted by the Definitions Subcommittee of the
Invasive Species Advisory Committee (ISAC)
Weeds As Examples
Weeds provide good examples to clarify what is meant by an invasive species because most people have a concept of what constitutes a “weed.”
Invasion can be thought of as a process that in our example, a plant must go through to become a successful, yet harmful invader. Several barriers must be overcome for a plant to be considered an invasive weed. Invasive weeds are invasive species.
Large-scale geographical barriers
First, a geographical barrier first must be overcome, which often occurs as a mountain range, ocean, or similar physical barrier to movement of seeds and other reproductive plant parts. Plants that overcome geographical barriers are known as alien plants or alien species. Alien plants are non-native plants and alien species are non-native species. Therefore, non-native plants are those that occur outside their natural range boundaries, and this most often is mediated by humans either deliberately or unintentionally.
Survival barriers
The second set of obstacles that a non-native plant must overcome is barriers to germination and survival in its new location. These typically are environmental barriers such as adequate moisture availability to allow successful germination and survival of seedlings that will continue to grow to maturity. Other physical barriers might be soil pH, nutrient availability, or competition for resources from neighboring plants.

Dispersal barriers

Established alien plants next must overcome barriers to dispersal if they are to continue on the process to become invasive weeds. Or simply put, they must spread from their site of establishment. For example, an established, terrestrial, alien plant that reproduces only by seed would be considered an invasive plant if it spreads from its establishment site more than 100 yards in about 5 years. Or, if an established, terrestrial, alien plant reproduces vegetatively, it would be considered an invasive plant if it spread more than 6 yards in 3 years from its establishment site. However, this movement or spread alone does not make this invasive plant a harmful invader or invasive weed.


To be labeled an invasive weed or harmful invader, the invasive plant must cause negative environmental effects and these may have associated negative economic effects. Just as importantly, however, the overall negative effects caused by an invasive plant must outweigh any beneficial effects to warrant designation as an invasive weed or invasive species. For example, we do not mean smooth brome, we do mean water hyacinth; we do not mean ?, we do mean zebra mussels.
Approved by ISAC April 27, 2006
Preamble: Executive Order 13112 – defines an invasive species as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.” In the Executive Summary of the National Invasive Species Management Plan (NISMP) the term invasive species is further clarified and defined as “a species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.” To provide guidance for the development and implementation of the NISMP, the National Invasive Species Council (NISC) and the Invasive Species Advisory Committee (ISAC) adopted a set of principles outlined in Appendix 6 of the NISMP. Guiding Principle #1 provides additional context for defining the term invasive species and states “many alien species are non-invasive and support human livelihoods or a preferred quality of life.” However, some alien species (non-native will be used in this white paper because it is more descriptive than alien), for example West Nile virus, are considered invasive and undesirable by virtually everyone. Other non-native species are not as easily characterized. For example, some non-native species are considered harmful, and therefore, invasive by some sectors of our society while others consider them beneficial. This discontinuity is reflective of the different value systems operating in our free society, and contributes to the complexity of defining the term invasive species.
NISC is engaged in evaluating and updating the 2001 NISMP and is developing comments for a revised action plan as required by the EO 13112. While there have been numerous attempts to clarify the term invasive species, there continues to be uncertainty concerning the use and perceived meaning of the term, and consequently over the prospective scope of actions proposed in the NISMP. Options related to private property use, pet ownership, agriculture, horticulture, and aquaculture enterprises may be affected depending upon the definition, use, and policy implications of the term.
Weeds As Examples (continued)
Establishment barriers
The third obstacle that a non-native plant must overcome to be considered an invasive weed, is to form a population that is self-sustaining and does not need re-introduction to maintain a population base such that it continues to
survive and thrive in its new environment. Once this occurs, this population of non-native plants is considered to be established. Environmental barriers to survival and establishment are similar.
Dispersal and spread barriers
Established non-native plants must overcome barriers to dispersal and spread from their site of establishment to be considered invasive plants. Additionally, the rate of spread must be relatively fast. However, this movement or spread alone does not necessarily make this non-native plant an invasive weed or invasive species.
Harm and impact
Finally, a plant is deemed to be invasive if it causes negative environmental, economic, or human health effects, which outweigh any beneficial effects. For example, yellow starthistle is a source of nectar for bee producers. But the displacement of native and other desirable plant species caused by yellow starthistle leads to dramatically decreased forage for wildlife and livestock, which severely disrupts the profitability of associated businesses. These negative effects greatly overshadow the positive effects and thus, define harm caused by yellow starthistle and explain why it is considered an invasive species.

In particular, the desire to consider a non-native species as ‘invasive’ may trigger a risk/benefit assessment process to determine whether regulatory action is warranted. All these uncertainties have stood and could continue to stand in the way of progress in actions and policy development to prevent new invasions and manage existing invasive species. While it is not the purpose of this white paper to define a risk/benefit assessment process, development of such a process must be open and efficient to minimize the uncertainties.

This white paper is intended to provide a non-regulatory policy interpretation of the term invasive species by identifying what is meant, and just as important, what is not meant by the term. ISAC recognizes that biological and ecological definitions will not precisely apply to regulatory definitions. We believe, however, that our clarification will apply to all taxa of invasive species in all habitats and furthermore, our explanation will be functional and acceptable to most stakeholders. ISAC simply wants to clarify what is meant and what is not meant by the term invasive species in the technical sense and to provide insight into those areas where societal judgments will be necessary to implement effective public policy.
The utility of our clarification should be in education, conflict resolution, and efficiency in the planning, prevention, control/eradication, and management of invasive species.
ISAC recommends that NISC adopt the clarifications presented in this white paper to foster progress for invasive species management in the United States.

An invasive species is a non-native species whose introduction does or is likely to cause economic or environmental harm or harm to human, animal, or plant health. The National Invasive Species Management Plan indicates that NISC will focus on non-native organisms known to cause or likely to cause negative impacts and that do not provide an equivalent or greater benefit to society. In the technical sense, the term ‘invasion’ simply denotes the uncontrolled or unintended spread of an organism outside its native range with no specific reference about the environmental or economic consequences of such spread or their relationships to possible societal benefits. However, the policy context and subsequent management decisions necessitate narrowing what is meant and what is not meant by the term invasive species. Essentially, we are clarifying what is meant and not meant by “causing harm” by comparing negative effects caused by a non-native organism to its potential societal benefits.
Perception to Cause Harm
Complications concerning the concept of invasive species arise from differing human values and perspectives. Differing perceptions of the relative harm caused or benefit gained by a particular organism are influenced by different values and management goals. If invasive species did not cause harm, we would not be nearly as concerned. Perceptions of relative benefit and harm also may change as new knowledge is acquired, or as human values or management goals change.
For a non-native organism to be considered an invasive species in the policy context, the negative effects that the organism causes or is likely to cause are deemed to outweigh any beneficial effects. Many non-native introductions provide benefits to society and even among species that technically meet the definition of invasive, societal benefits may greatly exceed any negative effects (for example crops and livestock raised for food). However, in some cases any positive effects are clearly overshadowed by negative effects, and this is the concept of causing harm. For example, water hyacinth has been popular in outdoor aquatic gardens but its escape to natural areas where its populations have expanded to completely cover lakes and rivers has devastated water bodies and the life they support, especially in the southeastern U.S. And, there are some organisms, such as West Nile virus, that provide almost no benefits to society at all. Such organisms constitute a small fraction of non-native species, but as a consequence of their ability to spread and establish populations outside their native ranges, they can be disastrous for the natural environment, the economies it supports, and/or public health. Because invasive species management is difficult and often very expensive, these worst offenders are the most obvious and best targets for policy attention and management.
The negative impact to a native species caused by an invasive species might trigger additional negative interactions for other associated native species; i.e., there could be direct and indirect effects. For example, an invasive weed that is undesirable as a food source may outcompete and displace native grasses and broadleaf plants. These displaced native grasses and broadleaf plants may have been primary forage for animals, which subsequently would be displaced to a new location or have their populations reduced because the weed invasion decreased the availability of food in their native plant and animal community. However, negative effects are not always characterized by a cascade of impacts realized throughout the environment. For example, simple displacement of an endangered species by a non-native species might alone provide sufficient justification to consider the non-native organism an invasive species.
What We Do Not Mean, What We Do Mean, and the “Gray” Area
Native and Non-native Species
Invasive species are species not native to the ecosystem being considered. Canada geese are native to North America and most of their populations migrate annually. However, in some locations in the U.S. (e.g. suburban Maryland; the Front Range of Colorado) introduced, non-migratory populations of Canada Geese are causing problems – such as fouling lawns, sidewalks, grass parks, and similar areas. While non-migratory populations can cause problems, they are not considered an invasive species because they are native. Additionally, Canada geese are of significant financial value to many local economies through waterfowl hunting and simple enjoyment. Mute swans, however, are invasive. Mute swans are native to Europe and Asia but were introduced into North America where their populations have increased dramatically. They compete directly with native waterfowl for habitat, displacing them, and that is why they are considered an invasive species. Whitetail deer populations have increased dramatically in the northeastern U.S. and are problems in farms, yards, and natural areas because they consume plants valued by humans; but are not invasive because they are native. Nutria, on the other hand, are another classic example of an invasive species. Nutria are native to South America but were introduced into North America where their populations have soared. Nutria compete directly with native muskrats, beavers, and other similar native species for habitat; often causing the displacement of these native species.
Feral Populations
It is also essential to recognize that invasive species are not those under human control or domestication; that is, invasive species are not those that humans depend upon for economic security, maintaining a desirable quality of life, or survival. However, the essential test is that populations of these species must be under control. Escaped or feral populations of formerly domesticated plants and animals would be considered invasive species if all the concepts and conditions are met as outlined in “Weeds Are Examples.” Cereal rye being produced on a farm in Kansas is considered very desirable, but feral rye on the breaks of the Poudre River in Colorado would be considered an invasive species because it is displacing native plants and the native animal communities they support. Domesticated goats on a farm in Texas are considered highly desirable, but feral goats in Haleakala National Park on Maui are considered an invasive species. Feral goats have severely overgrazed areas and eliminated native Hawaiian plants, which were never adapted to grazing. Areas denuded by feral goats have led to increased soil erosion.
A Biogeographical Context
An invasive species may be invasive in one part of the country, but not in another. A biogeographical context must be included when assessing whether a non-native species should be considered an invasive species. Lake trout are highly desirable in the Great Lakes where they are native, but are considered an invasive species in Yellowstone Lake. They compete with native cutthroat trout for habitat, which decreases their populations. Atlantic saltmarsh cordgrass is an essential component of east coast salt marshes, but is highly invasive on the west coast where it covers mudflats and displaces native estuarine plants and the community of animals they support, including huge flocks of migrating waterfowl. Kentucky bluegrass would be considered an invasive species in Rocky Mountain National Park in Colorado, but considered non-invasive a mere 60 miles away at a golf course in Denver. English ivy is considered a good ground cover species in the Great Plains and Midwest, but is a highly invasive weed in the forests of the Pacific Northwest and Eastern U.S. where it outcompetes native plants and displaces the associated animal communities.
The “Gray” Area
There are obvious examples of invasive species such as snakehead fish, yellow starthistle, or Phytophthora ramorum (the organism that causes sudden oak death); and there are obvious examples of species that are not invasive, namely native plants and animals. There are, however, non-native organisms for which it will be difficult to make a determination and these should be subject to assessment. Whether these non-native organisms will be considered invasive species will depend upon human values. For example, European honeybees are cultured to produce honey and pollination services, and even though they form wild populations in many parts of the country and occasionally create problems by building hives in the walls of homes or can be a human health problem for individuals that are highly allergic to their sting, most would not consider them an invasive species because they produce a desired food product.
Another gray area example would be native termites v. Formosan termites. No one wants termites in their homes but only Formosan termites would be considered an invasive species because they are non-native. Smooth brome also serves as another gray area example. It was imported from Russia in the 1890s for forage and was widely planted. It clearly has escaped cultivation and can be found in many natural areas particularly in the western U.S. but in most situations, smooth brome would not be considered an invasive species because of its forage value for wildlife and livestock.
Chinese or Oriental clematis serves as another gray area example. Chinese clematis (virgin’s bower, orange peel) is a popular ornamental that has been planted worldwide. However, it has escaped cultivation in several western states where its populations can spread, particularly in shrubland, on riverbanks, sand depressions, along roadsides, in gullies, and along riparian forests in hot dry valleys, deserts, and semi-desert areas. Escaped populations of Chinese clematis occur in Idaho, Nevada, Utah, New Mexico, and Colorado but so far, it is considered an invasive species only in Colorado where it has spread dramatically from its site of introduction and displaced native plant species.
Environmental Harm
We use environmental harm to mean biologically significant decreases in native species populations, alterations to plant and animal communities or to ecological processes that native species and other desirable plants and animals and humans depend on for survival. Environmental harm may be a result of direct effects of invasive species, leading to biologically significant decreases in native species populations.
Examples of direct effects on native species include preying and feeding on them, causing or vectoring diseases, preventing them from reproducing or killing their young, out-competing them for food, nutrients, light, nest sites or other vital resources, or hybridizing with them so frequently that within a few generations, few if any truly native individuals remain. Environmental harm includes decreases in populations of Federally Listed Threatened and Endangered Species, other rare or uncommon species and even in populations of otherwise common native species. For example, over three billion individual American chestnut trees were found in U.S. forests before the invasive chestnut blight arrived and virtually eliminated them. Environmental harm also can be the result of an indirect effect of invasive species, such as the decreases in native waterfowl populations that may result when an invasive wetland plant decreases the abundance of native plants and thus, decreases seeds and other food that they provide and that the waterfowl depend upon.
Environmental harm also includes significant changes in ecological processes, sometimes across entire regions, which result in conditions that native species and even entire plant and animal communities cannot tolerate. For example, some non-native plants can change the frequency and intensity of wildfires, or alter the hydrology of rivers, streams, lakes and wetlands and that is why they are considered invasive species. Others can significantly alter erosion rates. For example, trapping far more wind-blown sand than native dune species, or holding far less soil than native grassland species following rainstorms. Some invasive plants and micro-organisms can alter soil chemistry across large areas, significantly altering soil pH or soil nutrient availability. Environmental harm also includes significant changes in the composition and even the structure of native plant and animal communities. For example, the invasive tree Melaleuca quinquinervia, can spread into and take over marshes in Florida’s Everglades, changing them from open grassy marshes to closed canopy swamp-forests.
Environmental harm may also cause or be associated with economic losses and damage to human, plant and animal health. For example invasions by fire promoting grasses that alter entire plant and animal communities eliminating or sharply reducing populations of many native plant and animal species, can also lead to large increases in fire-fighting costs and sharp decreases in forage for livestock. West Nile virus is a well known human health problem caused by a non-native virus which is commonly carried by mosquitoes. West Nile Virus also kills many native bird species, causing drastic reduction in populations for some species including crows and jays.
Additional Examples of Impacts Caused by Invasive Species
Specific examples of the harm caused by invasive species are useful to further clarify the definition. The following list of examples is not meant to be comprehensive, but offers further explanation:
Impacts to Human Health
Respiratory infections: The outbreak of West Nile virus in the U.S. began in the Northeast in 1999 and has since spread throughout the country. Infections in humans may result in a flu-like illness and in some cases death. This outbreak has caused illness in thousands of citizens, increased medical costs for affected persons, and decreased productivity due to absence from work. West Nile virus also has affected horses and has caused widespread mortality in native birds (U.S. Centers for Disease Control, 2006).
Poisonous plants: Exposure to the sap of Tree-of-heaven/Chinese sumac tree has caused inflammation of the heart muscle (myocarditis) in workers charged to clear infested areas. Afflicted personnel experienced fever/chills, chest pain that radiated down both arms, and shortness of breath. Exposure occurred when sap from tree-of-heaven contacted broken skin. Such exposure has caused hospitalization, medical expense, and lost productivity due to absence from work (Bisognano et al. 2005).
Impacts to Natural Resources
Declines in wildlife habitat and timber availability: Chestnut blight is a disease of American chestnut caused by a non-native fungal pathogen that was introduced into eastern North America around 1910. The disease eliminated the American chestnut from eastern deciduous forests thereby decreasing timber harvests and wildlife that depended upon the American chestnut for habitat (USDA-APHIS/FS 2000).
European gypsy moth defoliates trees on millions of acres of northeastern and mid-western forests. It currently is found in 19 states causing an estimated $3.9 billion in tree losses and also decreased wildlife habitat (USDA-APHIS/FS 2000).
Decreased soil stabilization and interrupted forest succession: White pine blister rust is a disease of white pine species caused by the non-native fungal pathogen Cronartium ribicola. It was introduced into eastern North America around 1900 and western North America in 1920. It spread rapidly, killing off native white, whitebark, and limber pines, whose seeds are an important food source for birds, rodents and bears. Elimination of these trees caused by this pathogen alters forest ecosystems, eliminates wildlife forage, and decreases the soil stabilization effects of these trees, snowmelt regulation, and forest succession (Krakowski et al. 2003).
Changes in wildfire frequency and intensity: Cheatgrass decreases the interval between the occurrences of wildfires in the Great Basin region from once every 70 to 100 years to every 3 to 5 years because it forms dense stands of fine fuel annually. The decrease in interval between wildlfires causes increased risk to human life and property and also places at risk established communities of plants and animals that we consider desirable (Knapp 1996; Pimentel et al. 2000; USFWS 2003; Whisenant 1990).
Excessive use of resources: Tamarisk in the desert southwest use more than twice as much water annually as all the cities in southern California, which places this invasive weed in direct competition with humans for the most limiting resource in the southwestern U.S. (Friederici 1995; Johnson 1986).
Suppressors: Russian knapweed exudes toxins from its tissues that inhibit the growth of surrounding plants or eliminates them. Desirable plant communities are placed at risk from Russian knapweed invasion, which may result in decreased numbers of wildlife species or livestock that the invaded land otherwise could support. Russian knapweed also is very toxic to horses (Stevens 1986; Young et al. 1970a and 1970b).
Decreased carrying capacity for wildlife and livestock: Expansion of leafy spurge, yellow starthistle, or other unpalatable invasive weeds displace desirable forage plants and may allow fewer grazing animals to survive in infested areas (DiTomaso 2001; Lym and Messersmith 1985; Lym and Kirby 1987).
Impacts to Recreational Opportunities and Other Human Values
Decreased property values: Asian longhorned beetles first appeared in New York in 1996 and in Chicago in 1998. Larvae burrow into trees causing girdling of stems and branches, dieback of the crown, and can kill an entire tree. It infests many different tree species in the U.S. and is a threat to urban and rural forests (Cavey et al. 1998).
Emerald ash borers were first detected in the U.S. in 2002. They currently are found in Michigan, Ohio, and Indiana. Emerald ash borer larvae tunnel under bark of ash trees and could eliminate ash as a street, shade, and forest tree throughout the U.S. Estimated replacement cost in six Michigan counties is $11 billion and an additional $2 million in lost nursery sales (Chornesky et al. 2005).
Dutch elm disease was first introduced into the U.S. in 1927 and occurs in most states. Dutch elm disease has killed more than 60% of elms in urban settings and decreased the value of urban and suburban properties (Brasier and Buck 2001).
Spotted knapweed and leafy spurge expansion in the western U.S. have displaced desirable forage plants thereby decreasing the value and sales price of grazingland in the western U.S. (Maddox 1979; Weiser 1998).
Eurasian watermilfoil was introduced into the U.S in the 1940s and has since spread throughout much of the country. This submersed aquatic plant can form dense mats at the water surface limiting access, recreation, and aesthetics and thus, has decreased the values of shoreline properties in New Hampshire, the Midwest and elsewhere (Halstead et al. 2003).
Decreased sport fishing opportunities: Whirling disease is caused by a parasite (Myxobolus cerebralis) that most likely originated in Europe. It was first observed in the U.S. in 1958. The parasite attacks the soft cartilage of young trout causing spinal deformities and causes the fish to exhibit erratic tail-chasing behavior. Heavily infected young trout can die from Whirling disease and even if they recover, they remain carriers of the parasite. All species of trout and salmon may be susceptible and angling and the businesses supported by trout and salmon fishing may be at risk if this disease continues to spread (Aquatic Nuisance Species Task Force et al. 2005; Colorado Division of Wildlife 2006).
Smallmouth bass fishing in Lake Erie was closed during bass mating because of round goby predation of nests. Fishing was closed because male smallmouth bass aggressively guard nests from predators and are easier to catch by anglers during this time of year. Removal of males by anglers decreased the number of bass offspring because of increased round goby predation of unguarded nests (Steinhart et al. 2004). Businesses that smallmouth bass anglers patronize could be adversely affected by such closures.
Altered business opportunities: The concern over Sudden Oak Death Syndrome caused by the pathogen Phytophthora ramorum is causing drastic changes in available nursery stock by nurseries and landscape businesses. This clearly impacts the profitability of these businesses and choice by consumers and could devastate oak forests nationwide (Chornesky et al. 2005; Rizzo and Garbelotto 2003).
Annual harvests of oysters in Long Island Sound averaged over 680,000 bushels during 1991 through 1996. After Haplosporidium nelsonii (MSX) invaded in 1997 and 1998, oyster harvests decreased from 1997 through 2002 to an average annual harvest of 119,000 bushels with a low of 32,000 bushels in 2002. The overall ex-vessel value of oyster farming dropped 96% in 10 years from $45 million in 1992 to $2 million in 2002 (Sunila et al. 1999).
Non-native algae introduced into the Hawaiian Islands costs Maui alone about $20,000,000 annually due to algae fouling the beaches and subsequent lost tourism (Carroll 2004; Keeney 2004; Univ. Hawaii 2006).
Sea lampreys were introduced into Lakes Ontario and Erie during the construction of the Welland Canal and quickly spread to the other Great Lakes. The sea lamprey is a parasite that attaches itself to fish, eventually killing them, and has devastated commercial and recreational Lake Trout fishing in the Great Lakes (Lawrie 1970).
Australian spotted jellyfish were introduced into the Gulf of Mexico in 2000 and occurred in such massive numbers that shrimping operations were shut down because jellyfish clogged shrimp nets (Graham et al. 2003).
Altered ecosystems and recreational opportunities: The submersed aquatic plant hydrilla, forms dense canopies at the water surface that raise surface water temperatures, change pH, exclude light, and consume oxygen, resulting in native plant displacement and stunted sport fish populations. This example of an altered aquatic ecosystem caused by an invasive aquatic weed also negatively affects recreation and businesses that depend upon that human activity (Colle et al. 1987).
Invasive species are those that are not native to the ecosystem under consideration and that cause or are likely to cause economic or environmental harm or harm to human, animal, or plant health. Plant and animal species under domestication or cultivation and under human control are not invasive species. Furthermore for policy purposes, to be considered invasive, the negative impacts caused by a non-native species will be deemed to outweigh the beneficial effects it provides. Finally, a non-native species might be considered invasive in one region but not in another. Whether or not a species is considered an invasive species depends largely on human values. By attempting to manage invasive species, we are affirming our economic and environmental values. Those non-native species judged to cause overall economic or environmental harm or harm to human health may be considered invasive, even if they yield some beneficial effects. Society struggles to determine the appropriate course of action in such cases, but in a democratic society that struggle is essential.
Many invasive species are examples of "the tragedy of the commons," or how actions that benefit one individual's use of resources may negatively impact others and result in a significant overall increase in damage to the economy, the environment, or public health. In ISAC’s review of Executive Order 113112, the public domain is specifically represented; however, the implementation of the NISMP has prompted concerns over the rights of personal and private property owners. Property rights are of great importance in the U.S. and one outcome of the NISMP should be to recognize the right to self determination by property owners and promote collaboration on invasive species management. The right to self determination is an important concept in a democratic society, however, with that right comes personal responsibility and stewardship, which includes being environmentally responsible. The natural environment that our society enjoys, recreates in, and depends upon to support commerce must be conserved and maintained. Effective invasive species management is just one aspect of conserving and maintaining our nation’s natural environment, the economies it supports, and the high quality of life our society enjoys.

Aquatic Nuisance Species Task Force, U.S. Fish and Wildlife Service, and U.S. Coast Guard. 2005. Protect Your Waters. Harmful Aquatic Hitchikers: Others: Whirling Disease. [Online]
Bisognano, J.D., K.S. McGrody, and A.M. Spence. 2005. Myocarditis from the Chinese sumac tree. Annals Internal Medicine 143(2):159.
Brasier, C.M. and K.W. Buck. 2001. Rapid evolutionary changes in a globally invading fungal pathogen (Dutch elm disease). Biological Invasions 3:223-233.
Carroll, R. 2004. Maui battling seaweed invasion. Assoc. Press. [Online]
Cavey, J.F., E. R. Hoebeke, S. Passoa, and S.W. Lingafelter. 1998. A new exotic threat to North American hardwood forests: an asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae). I. Larval description and diagnosis. Proc. Entomol. Soc. Wash. 100 (2):373-381.
Chorensky, E.A., A.M. Bartuska, G.H. Aplet, K.O. Britton, J. Cummings-Carlson, F.W. Davis, J. Eskow, D.R. Gordon, K.W. Gottschalk, R.A. Haack, A.J. Hansen, R.N. Mack, R.J. Rahel, M.A. Shannon, L.A. Wainger, and T.B. Wigley. 2005. Science priorities for reducing the threat of invasive species to sustainable forestry. BioSci. 55(4):335-348.
Colle, D.E., J.V. Shireman, W.T. Haller, J.C. Joyce, and D.E. Canfield. 1987. Influence of Hydrilla on Harvestable Sport-Fish Populations, Angler Use, and Angler Expenditures at Orange Lake, Florida. North American Journal of Fisheries Management 7:410-417.
Colorado Division of Wildlife. 2006. Whirling disease and Colorado’s trout.
DiTomaso, J. 2001. Element stewardship abstract: Centaurea solstitialis L. Weeds on the web: The Nature Consevancy wildland invasive species program. ]tp://
Friedercici, P. 1995. The alien saltcedar. Am. For. 101:45-47.
Graham, W.M., D.L. Martin, D.L. Fedder, V.L Asper, and H.M. Perry. 2003. Ecological and economic implications of a tropical jellyfish invader in the Gulf of Mexico. Biological Invasions 5(1-2) 53-69.
Halstead, J.M., J. Michaud, S. Hallas-Burt, and J.P Gibbs. 2003. Hedonic analysis of effects of a nonnative invader (Myriophyllum heterophyllum) on New Hampshire (USA) lakefront properties. Environmental Management 32(3): 391-398.
Johnson, S. 1986. Alien plants drain western waters. The Nature Conservancy News, Oct-Nov 1986.
Keeney, T.R.E. 2004. Written testimony before the Subcommittee on Fisheries Conservation, Wildlife and Oceans, Committee on Resources, U.S. House of Representatives.
Knapp, P.A. 1996. Cheatgrass (Bromus tectorum L.) dominance in the Great Basin Desert: History, persistence, and influences to human activities. Global Environ. Change 6(1):37-52.
Krakowski , J., S.N. Aitken, Y.A. El-Kassaby. 2003. Inbreeding and conservation genetics in whitebark pine. Conservation Genetics 4:581-593.
Lawrie, A.H. 1970. The sea lamprey in the Great Lakes. Transactions of the American Fisheries Society 99:766-775.
Lym, R.G. and C.G. Messersmith. 1985. Cost effectiveness of leafy spurge control during a five-year management program. North Dakota Farm Res. 43(1)7-10.
Lym, R.G. and D.R. Kirby. 1987. Cattle foraging behavior in leafy spurge infested rangeland. Weed Technol. 1:314-318.
Maddox, D.M. 1979. The knapweeds: Their economics an biological control in the western states, U.S.A. Rangelands 1(4):139-141.
Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and economic costs of non-indigenous species in the United States. Biosci. 50(1):53-65.
Richardson, D.M., P. Pysek, M. Rejmanek, M.G. Barbour. F.D. Panetta, and C.J. West. 2000. Naturalization and invasion of alien plants: concepts and definitions. Diversity and Distributions 6:93-107.
Rizzo, D.M. and M. Garbelotto. 2003. Sudden oak death: Endangering California and Oregon forest ecosystems. Frontiers in Ecology and the Environment 1:197-204.
Steinhart, G.B., E.A. Marschall, and R.A. Stein. 2004. Round goby predation on smallmouth bass offspring in nests during simulated catch-and-release angling. Transactions of the American Fisheries Society 133: 121-131.
Stevens, K.L. 1986. Alleopathic polyacetylenes from Centaurea repens (Russian knapweed). J. Chem. Ecol. 12:1205-1211.
Sunila, I., J. Karolus, and J. Volk. 1999. A new epizootic of Haplosporidium nelsoni (MSX), a haplosporidian oyster parasite, in Long Island Sound, Connecticut. Journal of Shellfish Research 18(1): 169-174.
U.S. Fish and Wildlife Service, 2003. Costly fires hurt wildlife habitat. [Online]
Univ. of Hawaii. 2006. Invasive marine algae of Hawaii. [Online]
U.S. Center for Disease Control. 2000. Fight the Bite. [Online]
USDA-APHIS/FS. 2000. Draft pest risk assessment for importation of solid wood packing materials into the United States.
Weiser, C. 1998. Economic effects of invasive weeds on land values (From and agricultural banker’s standpoint). Proc. Colorado Weed Summit April 7-8, 1998. p. 35-38.
Whisenant, S.G. 1990. Changing fire frequencies on Idaho’s Snake River Plain: Ecological and management implications. The Station. Nov. 1990 (276) Ogden, UT: General Technical Report INT – USDA Forest Service Intermountain Research Station.
Young, S, W.W. Brown, and B. Klinger. 1970a. Nigropallidal encephalomalacia in horses caused by ingestion of weeds of the genus Centaurea. J. Amer. Vet. Med. Assoc. 157:1602-1605.
Young, S., W.W. Brown, and B. Klinger. 1970b. Nigropallidal encephalomalacia in horses fed Russian knapweed (Centaurea repens L.). Amer. J. Vet. Res. 31:1393-1404.
Appendix 4: On-line Resources
Weed Research and Information Center (WeedRIC) Pampasgrass and Jubatagrass Threaten California Coastal Habitats brochure:
California Horticultural Invasive Prevention partnership (CAL-HIP) PlantRight campaign
Missouri Botanical Garden’s Exotic Plant Pests page:
American Nursery & Landscape Association (ANLA):
Weed Science Society of America:
The Nature Conservancy:
The Nature Conservancy Invasive Species Initiative:
ISAC White Paper on Definition of Invasive Species:
National Invasive Species Council:
USDA’s Agricultural Research Service:
USDA’s National Arboretum:
USDA’a Henry A. Wallace Beltsville Agricultural Research Center:
USDA’s Agricultural Research Service’s Crop Production and Protection National Program:
USDA’s Agricultural Research Service’s Technology Transfer Office:
USDA’s Agricultural Research Service’s Research Project: Crop and Weed Responses to Increasing Atmospheric Carbon Dioxide:
USDA’s Natural Resource Conservation Service Plants Data Base:
Plant Variety Protection Act: provides an archive of images related to invasive species, with particular emphasis on educational applications.

[1] Executive Order 13112 defines an invasive species as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.” Also see Appendix 3.

[2] Biological systematics is the study of the diversity of living organisms through time and includes determining their taxonomic identities.
[3] Work at the Missouri Botanical Garden to compile a comprehensive inventory of the cultivated plants in North America was presented.
[4] Executive Order 13112 defines an invasive species as “a species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health (also see Appendix 3).

No comments: