For more copies of this publication, contact Associate
Director, Natural Resources Stewardship and Science,
National Park Service, P.O. Box 37127, Washington,
to this document include Roger Andrascik, Terry
Cacek, Robert Doren, Lissa Fox, Ron Hiebert,
Nonnative plants are invading the national parks,
causing tremendous damage to park resources.
Called exotics, aliens, non-indigenous species,
and weeds, these invasive nonnatives get into
the parks by various means. Seeds and plant parts
are brought into the parks by wildlife, wind,
water, and humans. Fast-growing nonnative plants
encroach from populations established outside
Once inside park boundaries, the most aggressive
of these nonnatives spread like wildfire into undisturbed
as well as disturbed areas. These invasive plants
often cause irreparable damage to natural resources.
The ecological balance of plants, animals, soil,
and water achieved over many thousands of years
is destroyed. As native plants are displaced, animal
populations that rely on the plants for food and
shelter also decline. Nonnative plants may reduce
or deplete water levels, or alter runoff patterns
and increase soil erosion, thus diminishing both
the land and water quality. Some nonnatives release
toxic chemicals into the soil or harbor diseases,
increasing the stress on native plants. Some nitrogen-fixing
nonnatives increase soil fertility, allowing other
nonnatives to outcompete plants that have evolved
in the nutrient-poor native soils. Nonnatives that
interbreed with native species can swamp native
gene pools. The growth and spread of nonnatives
can also change fire patterns and intensities,
resulting in an altered ecosystem.
Estimates indicate that nonnative plants infest
4,600 new acres of federal land each day. Each
year, nonnatives spread into an area larger than
the state of Delaware. Invasive nonnative plants
currently infest an estimated seven million acres
of National Park System lands. The National Park
Service spends millions of dollars each year combatting
these plants in an effort to preserve park resources,
and still the problem is not solved. Outside park
boundaries, federal, state, and local agencies
fight the same battles. Farmers lose millions more
trying to control nonnative plants that drastically
reduce land use and productivity.
Managing invasions of this magnitude requires
a coordinated strategy based on cooperation among
all land managers and on the principles of integrated
pest management. Since nonnative plants do not
recognize political or other jurisdictional boundaries,
they can only be managed if all land managers,
both private and public, work together. Given the
extent of nonnative plant infestations and the
associated costs for management, all available
resources should be shared and used efficiently.
This strategy, which emphasizes cooperation, education,
and science, and is based on integrated pest management
techniques, can provide a blueprint for successful
management of invasive nonnative plants on National
Park System lands.
The National Park Service is required by law to
keep the parks as unaltered by human activities
as possible. As early as 1933, National Park
Service policy recognized the harmful effects
of nonnative plants and animals. Today, the National
Park Service has a strong and clear policy on
managing nonnative species in the park. This
policy is strengthened by a definition of nonnative
species that is unique. The National Park Service
defines nonnative species as any animal or plant
species that occurs in a given location as a
result of direct, indirect, deliberate, or accidental
actions by humans. This definition allows the
National Park Service to recognize and distinguish
between changes to park resources caused by natural
processes of animals and plants, such as natural
range expansions, and those changes caused by
animals and plants introduced by humans.
The concepts of integrated
pest management and
adaptive management underlie National Park Service
nonnative plant management policies and this strategy.
Integrated pest management is a proven approach
to managing pest problems, including invasive nonnative
plants. Integrated pest management is based on
a sound understanding of the ecology and biology
of a pest and its environment, and is a form of
adaptive management. In adaptive management, information
about the resources managed is continuously developed
and used to make adjustments to management approaches.
The National Park Service has already shown a
commitment to managing nonnative plants through
cooperation and partnerships. The National Park
Service helped to organize several invasive nonnative
(exotic) pest plant councils. These councils bring
together resource management professionals from
local, state, and federal governments, private
organizations, universities, and the public to
coordinate and focus nonnative plant management
efforts and eliminate duplication of effort. The
National Park Service also participates actively
in developing multi-agency and multi-jurisdictional
nonnative plant management plans. The National
Park Service cooperates with the Department of
Transportation and the Natural Resources Conservation
Service to produce native plant materials for use
in revegetation projects during road construction
in parks. In Florida and Hawaii, the state governments,
the Agricultural Research Service, the U.S. Forest
Service, and the National Park Service are developing
and testing biological control agents.
Inside park boundaries, park managers are instituting
integrated pest management techniques to control
the spread of nonnative plant species while causing
minimal impact on the environment. As part of that
program, the National Park Service is testing mechanical,
chemical, and cultural management methods and biological
Unfortunately, these efforts have not stopped the
flow of aggressive nonnative plants into new
areas of the parks or adjoining lands. More must
be done. The National Park Service needs an adequately
funded management program based on strong partnerships,
cooperation, and credible science. The National
Park Service workforce and the public must be
made aware of the disastrous impacts aggressive
nonnative plant infestations have on ecosystems,
so that they will be supportive of and join management
efforts. The National Park Service must consider
nonnative plant management in all planning and
project development and implementation, and have
an integrated pest management program that is
adopted and applied throughout the National Park
System. Since some nonnative plants are relatively
benign, emphasis should be put on the plant species
that cause the most resource and ecosystem damage.
However, vigilance is required because environmental
or other conditions could change allowing nonnative
plants that appear benign to become invasive.
This document lays out strategies for reaching
the above invasive nonnative plant management goals.
All action items are intended to be examples, rather
than a comprehensive list of all that should be
done to manage invasive nonnative plants.
Nonnative plants are continuously introduced to
our lands and waters. Preventing the introduction
of these nonnative plants is the first line of
defense in protecting ecosystems from degradation.
It is also the most economical and efficient
means of management.
The National Park Service prevention program must
have both internal and external components. The
Service must prevent introduction of nonnative
plant species into National Park System units and
work with partners to develop national, regional,
and local prevention strategies.
Preventing nonnative plant introduction requires
constant vigilance. Seeds of nonnative plants arrive
in parks in the tire treads of cars, buses, trucks,
planes, bicycles, and even on shoes. Nonnative
seeds attach to the fur or feathers of wildlife
and pets that routinely move in and out of parks.
Plant materials such as native grasses or earth
fill materials brought in to revegetate disturbed
ground or for other valid management reasons can
contain the seeds of nonnative plants. Physical
forces such as wind and water also transport seeds
and other parts of invasive plants.
Preventing invasion of nonnatives depends on an
active and informed public and workforce. Everyone
must understand and do their part to ensure a park
environment free of invasive nonnative plant species.
A workforce skilled in the principles and techniques
of nonnative plant management is a critical component
of effective prevention and management. Contractors,
concessioners, permittees, and holders of rights-of-way
must also understand the influence their actions
have on park resources.
Develop and implement a park-based prevention
an early warning system to identify and eradicate
new infestations of nonnative plants
in the park. Train appropriate personnel to identify
invasive nonnative plants.
and maintain a park-based list of plant species
that have not yet invaded the park but
that are known to occur in the region and are likely
with other regulatory agencies in expediting listing
of invasive nonnative plants on state and
federal noxious plant lists.
with the Denver Service Center and the Natural
Resource Conservation Service to develop 'Best
Management Practices' for ground-disturbing activities.
all feeds used on National Park System lands are
free of invasive nonnative plants materials,
in concert with state programs.
all materials used in revegetation projects on
National Park System lands, including organic
fertilizers and plant materials, are free of nonnative
plant seeds or materials.
locally-grown native plant materials where available
in all appropriate vegetation projects
in order to maintain genetic integrity of local
inspections of contractor's equipment and materials
to prevent importation of nonnative seeds
into the park.
responsibilities for nonnative plant management
in permits and concessions contracts. Require commercial
users that disturb established vegetation to provide
bonds that are retained until sites are returned
to specified vegetative conditions.
Target: Provide park managers and the public with
acceptable native alternatives to non-native plant
guidelines for park managers describing appropriate
uses of commercial varieties of native
seeds and plant materials when seeds cannot be
with commercial and other interests to develop
programs, regulations, or legislation prohibiting
the sale of plants known to be highly invasive
or that are on prohibited lists.
with commercial and other interests to develop
and ensure availability of acceptable plant materials.
Disseminate information on sources of materials.
Modify National Park Service policy and guidelines
to include nonnative plant management
issues, as needed.
the circumstances under which National Park Service
resources may be used to manage nonnative
plants on adjacent non-federal lands as part of
a preventive strategy.
nonnative plant management issues in all appropriate
policy documents and guidelines,
including planning/design, maintenance, fire, law
enforcement, construction, and resource management.
park guidance concerning uses of nonnative plants
in park residences, including a list of
permitted and non-permitted imports.
Educate National Park Service employees and commercial
users (permittees, concessioners,
rights-of-way holders, etc.) about invasive nonnative
plant impacts on park resources.
nonnative plant management information at all levels
of Park Service training, including
planning/design, management, construction, interpretation,
maintenance, law enforcement, and resource management.
established media (electronic media, publications,
permits and contracts, etc.) to educate Park Service
employees and commercial users about nonnative
plant management issues.
with universities, state and federal agencies,
and private organizations, to develop educational
programs and courses for resource managers and
others responsible for managing nonnative plants.
in and conduct seminars or workshops on nonnative
and interpret the results of the latest research
on nonnative plants to resource managers,
interpreters, maintenance personnel, and others.
National Park Service employees to join and participate
in professional organizations or
societies concerned with nonnative plant management
with responsible agencies and the concerned public
to incorporate nonnative plant management
techniques into pesticide applicator training courses.
Increase public awareness
For any prevention or management effort to be successful,
the public must understand the threats posed
by nonnative plant species, change behavior that
results in the spread of nonnative plants, and
provide support for management efforts. To bring
about this understanding, the National Park Service
must reach a broad audience with a clearly articulated
The interpretation and education program in the
National Park Service reaches millions of people
annually, providing the Service with a broad-reaching,
well-established educational net work. Working
closely with natural resource managers, interpreters
can present current and accurate information. When
integrated with other agencies' educational networks,
such as the U.S. Department of Agriculture's Extension
Service and the Natural Resources Conservation
Service, the National Park Service will be able
to build support for nonnative plant management
Target: Increase public awareness of invasive
nonnative plant threats and build support for National
Park Service management efforts.
and disseminate, through all available outlets
both locally and nationally, educational materials
that increase awareness of, understanding of, and
support for the full range of nonnative plant management
a model code of ethics concerning the use of plant
materials through cooperative efforts
with other concerned groups, industries, and agencies.
in or create local area field days and other types
of meetings to highlight partners'
nonnative plant management projects or programs.
with other agencies to develop and disseminate
educational materials (publications, posters, videos,
World Wide Web, etc.) to the public, interested
organizations, and agency employees.
public support through volunteer nonnative plant
management projects and other activities.
with the plant production industry to prepare educational
materials that encourage the use of
native plant species in revegetation and landscaping.
Strategy: Inventory and monitor nonnative plants.
Early detection and treatment of new infestations
of invasive nonnative plants is an effective and
ecologically sound management approach. Strong
inventory and monitoring programs in the parks
provide the information needed to direct prevention
activities. Inventories provide baseline information
on presence, distribution, and size of extant nonnative
plant populations. Inventories also provide essential
information for planning, budgeting, and setting
priorities. Regular monitoring will spot nonnative
plant encroachments in time to take effective action
and can be used as a tool to measure the effectiveness
of management efforts. Monitoring is also needed
to determine whether land use and program objectives
are being met and whether specific management methods
are effective. This information can then be used
to make adjustments to the overall program or to
specific on-the-ground treatments.
Baseline information important for making decisions
includes species identification; locations of infestations;
acreage infested; density of plants; general plant
community makeup and presence of rare native plants;
environmental conditions such as soils, slopes,
and proximity to surface or groundwater; and level
of disturbance and current land use.
Assess the distribution and extent of invasive
nonnative plant populations
with the Servicewide Inventory and Monitoring Program
to initiate inventories that would gather
information needed to make invasive nonnative plant
monitoring for invasive nonnative plants into park
resource management programs.
with the National Biological Service [now the Biological
Resources Division of the U. S.
Geological Survey], Agricultural Research Service,
and others to develop standards for nonnative plant
inventories that would be used by all federal land
management agencies. (Until new standards are developed,
the inventory and mapping guidelines in the 'Guidelines
for Coordinated Management of Noxious Weeds in
the Greater Yellowstone Area,' USDA and DOI, 1992,
development of remote sensing and GIS technologies
for detecting and monitoring nonnative plants.
standardized data related to nonnative plants into
National Park Service planning and
data management tools such as NR-MAP and the Resource
Management Plan Database.
partnerships with adjacent land holders and with
county weed districts to share resources
in the preparation of landscape inventory maps.
that site-specific monitoring is included in plans
for construction, habitat manipulation,
and other activities that might increase the risk
of nonnative plant infestations.
Target: Assess trends in time and space and assess
effectiveness of management programs.
with the Agricultural Research Service and National
Biological Service [now the Biological
Resources Division of the U. S. Geological Survey]
in the development of monitoring technologies that
are efficient yet sensitive to rapid changes in
nonnative plant populations.
with the National Biological Service [now the Biological
Resources Division of the U. S.
Geological Survey], Agricultural Research Service,
and others to develop a standard database for storage
and retrieval of invasive nonnative plant inventory
data from all federal land-managing agencies.
other agencies, develop a technical manual describing
how to monitor and evaluate various
or inspect high-risk areas to detect new invasions
or range expansions. These areas
include construction sites and other disturbed
areas, roads, trails, livestock holding areas,
and streams that enter the park.
control programs to assess not only the reduction
of the targeted plant, but also the maintenance
or restoration of the native vegetation and fauna.
Strategy: Conduct research and transfer technology.
Ecological understanding is essential for successful
adaptive and integrated management of invasive
nonnative plants. Individual plant species respond
to a particular environmental condition based
upon life history, special adaptations, and ranges
of tolerances. It has also been demonstrated
that the vulnerability of habitats to invasion
varies among types and levels and frequency of
disturbance. Management priorities need to be
based upon ecological criteria and the feasibility
of control. To set these priorities, managers
need sound scientific information, including
information on dispersal, the life history of
specific species, and the ecological effects
of specific nonnative plants on given systems.
Under the principles of adaptive management, new
management techniques should be treated as experimental
and evaluated and adjusted accordingly. Working
together, scientists and resource managers must
gather sound scientific information, use the information
to develop management techniques, monitor the results
of the management activities, determine if clearly
stated objectives are being met, and modify activities
The National Park Service will rely upon the scientific
expertise of cooperating research agencies and
institutions to develop sound scientific information
for managing invasive nonnative plants. Agencies
such as the Agricultural Research Service and the
National Biological Service [now the Biological
Resources Division of the U. S. Geological Survey],
as well as universities, can provide invaluable
support for National Park Service management activities.
In addition to obtaining research, the National
Park Service should make efforts to share information.
Transferring research and resource management information
to other researchers, National Park Service employees,
and the public will improve research and management
effectiveness at all levels. Technologies communicated
to research peers will increase the knowledge base,
avoid duplicative effort, and provide information
for synthetic and modeling activities. Research
information communicated to land managers can be
applied directly to management. Research results
communicated to educators and trainers will increase
public awareness and the skills of technical staffs.
Target: Base species-based management priorities
on scientific and other resource-related information.
nonnative plants based on potential impacts to
cooperation with federal, state, and regional authorities,
rank nonnative plants on local, regional,
and national scales based on potential impacts
Target: Develop methods and models to predict the
invasiveness of nonnative plants.
case histories of highly invasive nonnative plants
that elucidate characteristics of invasiveness.
models to predict invasiveness. Test these models
on known invasive and innocuous nonnative
research to improve restoration techniques and
Target: Understand what factors influence the vulnerability
of specific habitats to invasion and the effects
of nonnative invasions on ecosystems.
on studies of invaded and non-invaded habitats
to determine characteristics of vulnerable
literature searches and prepare abstracts of ecosystem
effects of invasive nonnative plants
found in national parks and their environs.
types and degree of ecosystem effects of high-priority
nonnative plants or highly threatened
Target: Develop techniques to detect and prevent
nonnative plant invasions and to manage established
with cooperating agencies to identify key corridors
of invasion and transporters of nonnative
management alternatives that will improve an uninfested
ecosystem's ability to resist invasion
by nonnative plants.
alternative methods to retard nonnative plant invasion
of disturbed sites pending restoration
or recovery of the site.
with cooperating agencies to develop and test integrated
invasive nonnative plant management
programs for use in infested areas.
research and testing of new biological control
agents and development of biological control
technologies. Participate in multi-agency regional
weed technology centers.
Target: Communicate technologies, status, and trends.
with other organizations to develop risk assessment
models and other decision-making tools.
research and resource management information in
professional and popular periodicals.
management successes to provide models for other
areas and agencies.
and present research results at appropriate regional,
national, and international workshops
Strategy: Integrate planning and evaluation.
Integration of invasive nonnative plant management
into every aspect of planning-whether local, regional,
national, or project related-contributes directly
to the ultimate goal of prevention and management
of these invasive pests. Partnerships that integrate
planning are the key to success in the management
of invasive nonnative plants, since these plants
invade lands regardless of political or organizational
Target: Create partnerships designed to integrate
multi-agency groups to assist with the development
of nonnative plant management partnership
plans and program development. Ensure that planning
incorporates the concerns and issues of land managers
with similar invasive nonnative plant problems
and management issues.
use of resources such as personnel, equipment,
expertise, and information where appropriate.
sample contracts, partnership documents, and invasive
nonnative plant management plans available
to parks as examples.
sufficient financial support for successful nonnative
plant management programs.
Target: Create management plans based on sound
scientific experts in planning efforts to ensure
that ecological considerations are incorporated
into management, operational, and funding elements
with other agencies to develop uniform criteria
for measuring accomplishments in all major
areas of nonnative plant management.
Target: Increase program efficiency and consistency
in the parks.
nonnative plant management issues into planning
considerations in park and multi-park
information transfer among resource management,
operations, and planning staff in the parks to
ensure that plans are comprehensive.
inter- and intra-agency cross-cutting budgets that
reflect the amount and aim of each organization's
funding toward nonnative plant management. Incorporate
the funding plans into program, project, and operational
multi-agency funding requests that embody the total
nonnative plant program(s) being implemented
by all agencies within the identified area of operations
the effectiveness of nonnative plant control programs
and projects by developing criteria and
schedules for program and project evaluations for
all nonnative plant management programs.
other plans or programs that may affect or be affected
by nonnative plant issues.
Strategy: Manage invasive non-native plants.
Many park units throughout the National Park System
have instituted projects to manage individual
species of invasive nonnative plants. However,
there are still many parks that do not have a
viable nonnative plant management program. The
National Park Service must put nonnative plant
management high on the list of resource management
priorities, and see that every park with invasive
plants has a management program in place.
Target: Reduce populations of invasive nonnative
plants through an integrated pest management program
that incorporates chemical, biological, cultural,
and physical (mechanical) operations.
National Park Service guidance for invasive nonnative
regional integrated pest management programs in
cooperation with partners. Share scientific
expertise, organizational skills, and administrative
support among partners.
in the development of local invasive nonnative
plant management units.
locally developed management strategies.
that professional technical assistance is readily
available to every park.
a system for reviewing, approving, and reporting
new technologies and strategies to minimize the
adverse consequences of management practices
on the ecosystem, paying special attention to water
quality and threatened, endangered, or sensitive
and support biological control efforts. Support
careful pre-release testing of biological
control agents on non-target (native) species to
detect possible unwanted impacts.