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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
This study was supported by Grant No. 00-8100-0518-GR from the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), Plant Protection and Quarantine. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
Library of Congress Cataloging-in-Publication Data
Predicting invasions of nonindigenous plants and plant pests.
“Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants and Plant Pests in the United States.”
Includes bibliographical references and index.
ISBN 0-309-08264-1 (hardcover)
1. Nonindigenous pests—Control—United States. 2. Invasive plants—Control—United States. 3. Biological invasions—United States—Prevention. 4. Plant invasions—United States—Prevention. I. National Academy Press (U.S.) II. National Research Council. Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants and Plant Pests in the United States.
SB990.5.U6 P74 2002
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Cover: Clockwise, from top left: Larvae of Asian long-horned beetle (Anoplophora glabripennis) in wood, USDA Forest Service. Dead American chesnut (Castanea dentata), spores of fungus Cryphonectria parasitica in background, William MacDonald, West Virginia University. Hemlock woolly adelgid (Adelges tsugae Annand), Kathleen Shields, USDA Forest Service. Fountain grass (Pennisetum setaceum), Richard Mack, Washington State University.
Printed in the United States of America
Copyright 2002 by the National Academy of Sciences. All rights reserved.
THE NATIONAL ACADEMIES
National Academy of Sciences
National Academy of Engineering
Institute of Medicine
National Research Council
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COMMITTEE ON THE SCIENTIFIC BASIS FOR PREDICTING THE INVASIVE POTENTIAL OF NONINDIGENOUS PLANTS AND PLANT PESTS IN THE UNITED STATES
RICHARD N. MACK, Chair,
Washington State University
SPENCER C. H. BARRETT,
University of Toronto
PETER L. DEFUR,
Virginia Commonwealth University
WILLIAM L. MACDONALD,
West Virginia University
LAURENCE VINCENT MADDEN,
The Ohio State University
DAVID S. MARSHALL,
Texas A&M University
DEBORAH G. MCCULLOUGH,
Michigan State University
PETER B. MCEVOY,
Oregon State University
JAN P. NYROP,
SARAH ELIZABETH HAYDEN REICHARD,
University of Washington
KEVIN J. RICE,
University of California, Davis
SUE A. TOLIN,
Virginia Polytechnic Institute and State University
ROBIN SCHOEN, Project Director
LUCYNA K. KURTYKA, Project Officer
KAREN L. IMHOF, Project Assistant
NORMAN GROSSBLATT, Editor
BOARD ON AGRICULTURE AND NATURAL RESOURCES NATIONAL RESEARCH COUNCIL
HARLEY W. MOON, Chair,
Iowa State University
CORNELIA B. FLORA,
Iowa State University
ROBERT B. FRIDLEY,
University of California, Davis
BARBARA P. GLENN,
Federation of Animal Science Societies, Bethesda, Maryland
W.R. (REG) GOMES,
University of California, Oakland
LINDA F. GOLODNER,
National Consumers League, Washington, D.C.
PERRY R. HAGENSTEIN,
Institute for Forest Analysis, Planning, and Policy, Wayland, Massachusetts
GEORGE R. HALLBERG,
The Cadmus Group, Inc., Waltham, Massachusetts
GILBERT A. LEVEILLE,
McNeil Consumer Healthcare, Denville, New Jersey
Cargill, Inc., Minneapolis, Minnesota (retired)
TERRY L. MEDLEY,
DuPont Biosolutions Enterprise, Wilmington, Delaware
WILLIAM L. OGREN,
U.S. Department of Agriculture (retired)
ALICE N. PELL,
NANCY J. RACHMAN,
Novigen Sciences, Inc., Washington, D.C.
G. EDWARD SCHUH,
University of Minnesota
BRIAN J. STASKAWICZ,
University of California, Berkeley
JOHN W. SUTTIE,
University of Wisconsin, Madison
JAMES H. TUMLINSON, III,
U.S. Department of Agriculture, Agricultural Research Service
JAMES J. ZUICHES,
Washington State University
CHARLOTTE KIRK BAER, Director
JULIE ANDREWS, Senior Project Assistant
BOARD ON LIFE SCIENCES
COREY S. GOODMAN, (Chair)
University of California, Berkeley, California
MICHAEL T. CLEGG,
University of California, Riverside, California
DAVID S. EISENBERG,
University of California, Los Angeles, California
DAVID J. GALAS,
Keck Graduate Institute of Applied Life Science, Claremont, California
Texas A&M University, College Station, Texas
JAMES M. GENTILE,
Hope College, Holland, Michigan
DAVID V. GOEDDEL,
Tularik, Inc., South San Francisco, California
ELLIOT M. MEYEROWITZ,
California Institute of Technology, Pasadena, California
ROBERT T. PAINE,
University of Washington, Seattle, Washington
STUART L. PIMM,
Columbia University, New York, New York
JOAN B. ROSE,
University of South Florida, St. Petersburg, Florida
GERALD M. RUBIN,
Howard Hughes Biomedical Research, Chevy Chase, Maryland
RONALD R. SEDEROFF,
North Carolina State University, Raleigh
ROBERT R. SOKAL,
State University of New York, Stony Brook, New York
SHIRLEY M. TILGHMAN,
Princeton University, Princeton, New Jersey
RAYMOND L. WHITE,
DNA Sciences, Inc., Fremont, California
FRANCES SHARPLES, Director
BRIDGET K.B. AVILA, Senior Project Assistant
This report is the product of many individuals. This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report:
MAY R. BERENBAUM, University of Illinois
CHARLOTTE R. BRONSON, Iowa State University
DONALD DAHLSTEN, University of California, Berkeley
JEFF DANGL, University of North Carolina
STUART H. GAGE, Michigan State University
ROBERT P. KAHN, Rockville, Maryland
ANDREW M. LIEBHOLD, US Department of Agriculture, Forest Service, West Virginia
SVATA M. LOUDA, University of Nebraska
KIRK A. MOLONEY, Iowa State University
MARCEL REJMÁNEK, University of California, Davis
DANIEL SIMBERLOFF, University of Tennessee
DONALD L. WYSE, University of Minnesota
Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. Dr. W.R. Gomes of the University of California oversaw the review of this report. Appointed by the National Research Council, Dr. Gomes was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.
Finally, we would like to thank the staff for this project, including Robin Schoen, Study Director, Lucyna Kurtyka, Staff Officer, Karen Imhof, Project Assistant, and Norman Grossblatt, Editor.
As the United States faces biological warfare for the first time and ponders the consequences of growing genetically modified crops, a largely unnoticed biological attack is underway; actually, it has been under way for centuries and shows no signs of slowing. Nonindigenous species—animals, plants, and microorganisms occurring beyond their original geographic ranges—are flowing into this country at a remarkable rate. Often unchecked by natural enemies or forces that modulate their numbers, many of these will become invasive pests that threaten human, animal, and plant health. America’s plant resources have been most affected, as foreign plants, arthropods, and plant pathogens attack our crops, gardens, urban treescapes, pastures, rangelands, natural forests, wetlands, prairies, and deserts. From coast to coast, there is hardly a place in the country untouched by invasive nonindigenous species.
In 1999, President Clinton established the National Invasive Species Council, which is composed of the heads of eight federal agencies, to develop a coordinated plan for managing nonindigenous invasive species. By one estimate, the toll of these species in lost crops and the cost of containment measures such as mechanical destruction, and the use of pesticides and biological control—is $137 billion per year. The indirect and ecological costs of losing native species because of attacks by or competition with invasive species may be incalculable. Moreover, while farmers, as caretakers of agricultural lands, have taken action to control pests in their fields, invasions into natural ecosystems have received far less attention; in many cases, there is little attempt to stop what some environmentalists describe as the “biological pollution” devastating our natural areas.
As a result, current estimates of the present and future costs of invasive species are almost certainly low.
The processes that facilitate the damage caused by invasive plants and plant pests once they are here are not well understood, but there is consensus that the increased rate at which these species are being introduced into the United States is the result of growth in trade with other countries and growth in worldwide tourism and travel. The sheer magnitude of those activities makes it virtually impossible to implement adequate systems for detecting known, unwanted plant pests as they arrive in cargo or with passengers at U.S. ports and move across borders. For example, the desire of gardeners and plant-lovers for “exotic” plants has fueled an influx, via mail and other import routes, of the seeds and cuttings of nonindigenous plants whose potential for invasiveness is unmonitored.
As the first line of defense against the entry of harmful nonindigenous species, the Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) faces an onerous task. The service is “to facilitate exports, imports, and interstate commerce in agricultural products and other commodities that pose a risk of harboring plant pests or noxious weeds in ways that will reduce, to the extent practicable, as determined by the Secretary, the risk of dissemination of plant pests or noxious weeds.” APHIS must operate, therefore, in an environment of competing priorities—one to facilitate trade and the other to protect plant life from the adverse byproducts of trade. Supporters of each of those priorities—for example, importers of foreign produce versus domestic growers or the landscape industry versus the stewards of national parks—place APHIS practices and decisions under close scrutiny.
With resources to conduct spot checks of less than 2% of all incoming shipments at borders, air, and seaports, APHIS cannot reasonably rely on detection to screen out known nonindigenous species that are “hitchhiking” on imports. It must therefore estimate the economic and environmental risks associated with allowing the entry of a foreign commodity or crop. On the basis of such estimates, APHIS has the authority to prohibit imports, but not without yet another hurdle. Its decisions are bound by international trade law to be supported by scientific evidence. Thus, erecting a science-based system to identify potentially harmful nonindigenous plants, pathogens and arthropods has arisen from both national and international mandates. But that requirement places a heavy burden on our current knowledge of organisms and their potential behavior in a novel environment. Of all the factors considered when estimating risk, behavior in a new environment is the one for which the least information is available.
The National Research Council established the Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants and Plant Pests in the United States in response to a request from APHIS to evaluate the state of scientific knowledge about biological invasions and the state of our ability to reliably predict the outcome of an accidental or intentional introduction of a nonindigenous species. Such information is important to APHIS as it makes
regulatory decisions, and it is critical for our understanding of the behavior of harmful invasive species and of how we might curb their expansion and impact.
The committee was given the charge to
Consider the historical record of weed, pathogen, and arthropod invaders, including pathways of their introduction
Identify and analyze circumstances that could allow nonindigenous species to become invaders, considering the biotic and abiotic characteristics of potentially affected ecosystems, including agricultural systems, and the characteristics of nonindigenous plants and pests of plants that contribute to their potential invasiveness
Determine the extent to which scientific principles and procedures can characterize the invasive potential of nonindigenous pests of plants and the degree of uncertainty intrinsic in such characterizations
Identify research that could improve the prediction of invasiveness
This report summarizes the results of the committee’s investigations. Our study was driven by the need to clarify the boundaries of current scientific knowledge and to guide the direction of our national effort to address the future introduction of harmful nonindigenous species.
Richard N. Mack, Chair,
Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants and Plant Pests in the United States