National
Management Plan: Introduction
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[Executive
Summary] | [Introduction] | [Survey
of Federal Roles &
Responsibilities] | [An Action
Plan for the Nation] | [Conclusion]
| [Appendices]
The
Problem
Invasive species are everywhere.
They damage our crops, our industries, the environment and public
health. Scientists, academics, leaders of industry and land managers
are realizing that invasive species are one of the most serious
environmental threats of the 21st century (Mooney and Hobbs 2000).
For centuries people have moved
plants, animals, and microbes around the world. Most countries
now rely on plants and animals from other regions of the world
in order to meet their dietary needs. People in the U.S. also
import plants and animals, and their products, for such things
as construction materials, ornamental plants, and pets. Organisms
that have been moved from their native habitat to a new location
(often in a different country) are typically referred to as "non-native,"
"nonindigenous," "exotic," or "alien"
to the new environment. A small percentage cause serious problems
in their new environments and are collectively known as "invasive
species." Most of U.S. food crops and domesticated animals
are non-native species and their beneficial value is obvious
- for example managed livestock are examples of non-native species
which are not invasive.
An "invasive species"
is defined by the Executive Order as a species that is 1) non-native
(or alien) to the ecosystem under consideration and 2) whose
introduction causes or is likely to cause economic or environmental
harm or harm to human health. The Order further provides that
a Federal agency may make a determination that the benefits of
an action, which may lead to the introduction or spread of an
invasive species, clearly outweigh the potential harm caused
by the species and take steps to minimize that harm (Executive
Order 13112, Appendix 1). This
Management Plan is focused on those non-native species that cause
or may cause significant negative impacts and do not provide
an equivalent benefit to society.
Invasive species have been introduced
in a variety of ways. The means and routes by which they are
introduced are called invasion "pathways." Some non-native
species, intentionally introduced for beneficial purposes, later
turn out to be invasive. In the U.S., examples include purple
loosestrife, which is sold as an ornamental plant, as well as
saltcedar which was introduced for erosion control. Many invasive
species are unintentionally introduced; they move as unknown
stowaways and "hitchhikers" when people and their products
are transported by air, water, rail, or road. Examples of invasive
species unintentionally introduced into the U.S. include chestnut
blight, the naval shipworm, and imported fire ants. Chestnut
blight is one of the most destructive plant diseases ever recorded.
This fungus, believed to have come from Asia in imported wood,
has forever changed the forest tree composition in the eastern
United States. The naval shipworm was introduced into San Francisco
Bay via wooden ships in the early part of the 20th century. It
excavated the majority of the wood pilings, causing warehouses
and loaded freight cars to fall into the Bay. Imported fire ants
entered the U.S. with soil removed from ships that transported
goods to the U.S. As their name suggests, they cause painful
stings. Where they have established in the southern U.S., they
can be found in large numbers. They can seriously injure livestock,
pets, and humans. They also feed on crops and build large, hard
mounds that damage farm and field machinery.
Invasive species can take a heavy
economic toll. Researchers at Cornell University estimate that
invasive species are costing Americans approximately $137 billion
every year (Pimentel et al. 2000). Even controlling a
single unwanted invader can carry a price tag in the millions.
The United States and Canada are spending $14 million a year
just to control the sea lamprey. This species caused the collapse
of the lake trout and whitefish fisheries in the Great Lakes
(Wilkinson pers. comm.). In 1994, the impacts of invasive plants
in the United States were estimated at $13 billion per year (Westbrooks
1998). The list of invaders is long, and the cost of prevention
and control is high and going up.
The environmental costs of invasive
species can also be staggering. Invasive species typically have
high reproductive rates, disperse easily, and can tolerate a
wide range of environmental conditions. Often, they lack predators
in their new environments. As a result, invasive species may
out-compete native species for prey or other resource needs (e.g.,
breeding sites). They may also prey upon native species, spread
pathogens and parasites, or alter the genetic make up of closely
related species. Wilcove et al. (1998) estimate that invasive
species have contributed to the placement of 35 to 46 percent
of the plants and animals on the Federal Endangered Species List.
The brown tree snake is a well-known example -- it arrived in
the U.S. territory of Guam in the 1940s, probably hidden in military
transport planes. It is mildly venomous and an aggressive predator
that has driven nine of Guam's eleven native land bird species
to extinction.
Invasive plants are estimated
to infest 100 million acres in the United States. Every year,
they spread across three million additional acres, an area twice
the size of Delaware. Every day, up to 4,600 acres of additional
Federal public natural areas in the Western continental United
States are negatively impacted by invasive plant species (Bureau
of Land Management 1996).
Invasive species have also dramatically
modified habitats. In some cases, invasive species have altered
the ecology of an area to such an extent that the original ecosystem
is fundamentally changed. For example, in the U.S., cheatgrass
has accelerated the fire cycle in western States by twenty-fold,
while saltcedar has altered soil chemistry and impacted native
plants and wildlife.
Some invasive species threaten
plant, animal, and/or human health. Pathogens and parasites may
themselves be invasive species or may be introduced by them (invasive
vectors). Bubonic plague is perhaps history's most infamous example
of a vectored disease. It was spread by non-native black rats
carrying disease-infected fleas. The recently introduced West
Nile virus, which is transmitted to humans by mosquitoes that
feed on the blood of infected animals, now threatens people and
animals in 12 eastern states and the District of Colombia. Cholera
and microorganisms that cause certain types of harmful algal
blooms are moved in the ballast water carried by large ships.
In many cases, invasive species
cause a combination of economic, environmental, and health threats.
Typically, studies which document the harm caused by invasive
species conclude that the U.S. needs to strengthen its legal
authorities and existing programs. A 1993 report by the Office
of Technology Assessment, "Harmful Non-indigenous Species
in the United States," states that "Federal laws leave
both obvious and subtle gaps in the regulation of harmful NIS
[invasive species]" (U.S. Congress, OTA 1993). The 1999
report compiled by the National Plant Board for the Animal and
Plant Health Inspection Service, "Safeguarding American
Plant Resources," notes that the laws giving the agency
its authorities "were passed in response to specific plant
health crises" and that "overlaps and gaps in this
array of statutes often leave the Agency unsure of which authority
to apply in any given case
" (National Plant Board
1999). A 1996 publication by The Nature Conservancy notes that
the laws that do exist often are not effective or adequately
enforced (Stein and Flack 1996). A recent review by Cornell University
researchers concludes, "Although [Federal] policies and
practices may help reduce accidental and intentional introduction
of potentially harmful exotic species [invasive species], there
is a long way to go before the resources devoted to the problem
are in proportion to the risks" (Pimentel et al.
2000).
Efforts by the U.S. (and all
other countries) to prevent the introduction and control the
spread of invasive species face a number of challenges:
- Determining whether a non-native
species is invasive requires a context-specific analysis. For
example, a species may cause harm in one type of ecosystem, but
not others. Because ecosystems are dynamic, their vulnerability
to invasion changes over time. Thus, it would be impossible to
develop a definitive or complete list of invasive species at
the national level. A limited number of invasive species are
listed as regulated species under Federal laws governing specific
types of species such as noxious weeds, injurious fish or wildlife
species, or aquatic nuisance species. States also compile lists
of invasive species under their authorities. Although incomplete,
this information can be used in setting priorities.
- Estimates of the number of non-native
species that have been introduced into the United States vary
widely (from 5,000 to as many as 50,000) (Pimentel et al.,
2000). The Office of Technology Assessment report estimates that
10 to 15 percent of introduced species will become established
and about 10 percent of established species may become invasive
(U.S. Congress, OTA 1993). Many additional species could create
problems if introduced. For example, the Animal and Plant Health
Inspection Service (APHIS) of the Department of Agriculture has
intercepted 7,400 species of plant pests at ports of entry since
1985 that some of which could have become invasive if they entered
the United States (APHIS unpublished data).
- The diversity and number of
pathways complicate efforts to prevent introduction and control
the spread of invasive species. Green crabs may have hitchhiked
in bait shipments, while citrus canker is carried on citrus trees.
Many pathways are unknown and pathways have a tendency to change
overtime.
- Once an invasive species becomes
established at a new location, it may spread. The pace of establishment
and spread depends on numerous factors, including the invasive
species' reproduction mechanisms, ability to acclimatize or adapt,
whether it has predators or competitors, and what pathways are
available for further movement.
In response to the threats posed
by invasive species and the challenges to minimizing their spread,
the President issued Executive Order 13112 (Order) on Invasive
Species, February 3, 1999 (Appendix
1).
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Executive
Order 13112 on Invasive Species
In 1997, 500 scientists and resource
managers wrote to the Vice President and requested action on
invasive species. Their letter stated: "We are losing the
war against invasive exotic species, and their economic impacts
are soaring. We simply cannot allow this unacceptable degradation
of our Nation's public and agricultural lands to continue."
An interagency team was launched in response to develop a comprehensive
and coordinated strategy for the problem. The team prepared a
review of the issue with recommendations, foremost among them
was that an executive order be issued providing standards and
a framework for ongoing action.
The Order applies to all Federal
agency whose actions may affect the status of invasive species
and requires agencies to identify such actions and to the extent
practicable and permitted by law (1) take actions specified in
the Order to address the problem consistent with their authorities
and budgetary resources; and (2) not authorize, fund, or carry
out actions that it believes are likely to cause or promote the
introduction or spread of invasive species in the United States
or elsewhere unless, "pursuant to guidelines that it has
prescribed, the agency has determined and made public its determination
that the benefits of such actions clearly outweigh the potential
harm caused by invasive species; and that all feasible and prudent
measures to minimize risk of harm will be taken in conjunction
with the actions" (Executive Order 13112, Appendix
1). Although the Order applies to all Federal agencies, most
of the duties required by the EO are the responsibility of the
eight Council members. Given the scope and complexity of the
invasive species problem, it is necessary to prioritize actions
to deal with the most pressing invasive species problems first.
The Order establishes the National
Invasive Species Council (Council), which is chaired by the Secretaries
of Agriculture, Commerce, and the Interior and includes the Departments
of State, Treasury, Defense, and Transportation and the Environmental
Protection Agency. Throughout this document, the term "Invasive
Species Council" or "the Council" means the eight
member Departments and their constituent agencies, as well as
a small staff assigned specifically to the Council. The Order
directs the Secretary of the Interior to establish an advisory
committee including diverse stakeholders to assist the Council
(Advisory Committee), to appoint an executive director with concurrence
of the other co-chairs, and to provide necessary staff and administrative
support. Current Advisory Committee members are listed in Appendix 4.
The Order directs the Council
to provide national leadership and oversight on invasive species
and to see that Federal agency activities are coordinated and
effective. In addition, the Council has specific responsibilities
including: promoting action at local, State, tribal, and ecosystem
levels; identifying recommendations for international cooperation;
facilitating a coordinated network to document, evaluate, and
monitor invasive species' effects; developing a web-based information
network on invasive species; developing guidance on invasive
species for Federal agencies to use in implementing the National
Environmental Policy Act; and preparing this document - the National
Invasive Species Management Plan.
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National
Invasive Species Management Plan
Requirements of the Order. The Council was directed by the President
to release the first edition of the Plan eighteen months after
the Order was issued, and to include performance-oriented goals
and objectives and specific measures of success for Federal agency
efforts concerning invasive species, including objectives and
measures for each of the Federal agency and Council duties described
above. The Plan is also to identify the personnel, other resources,
and additional levels of coordination needed to achieve its goals
and objectives. The purpose of the Plan is to provide a blueprint
for Federal action (in coordination with State, local, and private
programs and international cooperation) to prevent the introduction
of invasive species, provide for their control, and minimize
their economic, environmental, and human health impacts. The
focus of the Plan is on those non-native species that cause or
may cause significant negative impacts and do not provide an
equivalent benefit to society.
The Order requires that the Plan
be developed through a public process and in consultation with
Federal agencies and stakeholders. The first edition of the Plan
is to include a review of existing and prospective approaches
and authorities for preventing the introduction and spread of
invasive species, including those for identifying pathways by
which invasive species are introduced and for minimizing the
risk of introductions via those pathways. Based on this review,
the Plan is to identify research needs and recommend measures
to minimize the risk of introductions. The Order states that
those measures are to provide for a science-based process to
evaluate risks associated with introduction and spread of invasive
species and a coordinated and systematic risk-based process to
identify, monitor, and interdict pathways that may be involved
in the introduction of invasive species. If any recommended measures
are not authorized under current law, the Council is charged
with recommending legislative proposals for new authority.
The Council is required to update
the Plan biennially and report on success in achieving its goals
and objectives. Within 18 months after measures have been recommended
by the Council in any edition of the Plan, each Federal agency
whose action is required to implement such measures is required
to take the action recommended or provide the Council with an
explanation of why the action is not feasible.
The Management Plan: 1st Edition
This first edition of the Plan
is the result of extensive consultation with many organizations
and individuals with differing interests. Valuable guidance came
from the Invasive Species Advisory Committee and members of six
working groups made up of both Federal and non-federal experts
under the auspices of the Advisory Committee (Appendix
6). The working groups are: (1) international, (2) communication,
outreach, and education, (3) policy and regulation, (4) risk
analysis and prevention, (5) management, and (6) research, information
sharing, documentation, and monitoring. This Plan contains a
number of actions recommended by the working groups and discussed
in the reports of the groups. These are available for review
at the Council's Web site, www.invasivespecies.gov.
The Council also heard from a
wide range of organizations and individuals at five public listening
sessions held in July 2000 around the country and through numerous
written comments. In addition, the Advisory Committee and the
Council adopted a set of Guiding Principles, which are located
in Appendix 6 of this document.
The Council provided a 60-day public comment period on the Draft
Management Plan that ended December 1, 2000. As a result, the
Council received 181 written comments on the Plan, a few of which
were signed by multiple groups or individuals. The majority of
the submissions were from non-federal stakeholders. The input
from all of these processes is reflected in this edition of the
Plan. Although a draft Plan was made available for comment on
the Council's Web site in early August of 2000, before the deadline
set by the EO, the final version is being issued five months
after the EO's deadline, due to extensive revisions made in response
to public comment and delays in hiring Council staff.
This first Plan provides a general
blueprint for action to deal with the threats posed by invasive
species; however, many of the details of the actions called for
will require further development in the implementation phase.
At that point specific measures of success as well as personnel
and other resources needed to achieve the Plan's goals will be
described. The action items included in the Plan outline an array
of prospective approaches for preventing the introduction and
spread of invasive species. The Plan requires agencies to report
on their invasive species activities and steps taken to comply
with the Order and with the Plan, and provides for an oversight
mechanism to ensure agency compliance.
Clearly, many of the actions
and goals outlined in the Plan will not succeed unless they are
undertaken in cooperation with stakeholders that have extensive
programs dealing with invasive species, including other nations,
States, tribes, and local governments. The essential and often
leading role of State and local efforts and the importance of
coordinated Federal and State action are mentioned throughout
this edition. It was not within the scope of the Plan to report
on or analyze the myriad State and local invasive species programs
or plans, although, such an analysis would clearly be useful.
As appropriate, coordination with State and local programs and
plans will be addressed in the Plan's implementation phase.
Our efforts to minimize the spread
of invasive species have begun. Along the way, we will need to
more efficiently use our existing resources, as well as obtain
additional and sustained resources, both human and financial.
This edition of the Plan provides a blueprint for immediate action.
To make tangible progress we need to ensure that this Plan is
promptly implemented and that future editions follow in a timely
manner. We can meet the challenge of invasive species by harnessing
the energy, resources and intellect of all concerned.
Invasions
in the San Francisco Estuary
The San Francisco Bay/Delta Estuary
is an example of how species invasions can change an entire ecosystem.
It is possibly the most invaded estuary in the entire world (Cohen
and Carlton 1998). More than 230 non-native species have become
established in the system, and there are an additional 100-200
species that may be non-native but whose origin cannot yet be
determined. The known invasive species cover a wide range of
taxonomic groups: 69 percent of the species are invertebrates
such as mollusks, crustaceans, and tubeworms; 15 percent are
fish and other vertebrates; 12 percent are vascular plants; and
4 percent are microbial organisms. Non-native organisms dominate
many estuarine habitats, accounting for 40 to 100 percent of
the common species at many sites in the estuary, whether calculated
as a percentage of the number of species present, the number
of individuals, or of total biomass (Cohen and Carlton 1995).
In some areas, it is difficult to find a native organism.
Non-native species introductions
have dramatically reduced some native populations, altered habitat
structure and energy flows, and caused billions of dollars in
economic damage (Cohen and Carlton 1995). The pace of invasion
is apparently accelerating. Roughly half of the non-native species
have arrived in the last 35 years. Between 1851 and 1960, a new
species was established in the estuary every 55 weeks. From 1961
to 1995, the rate was a new species every 14 weeks (Cohen and
Carlton 1998).
A number of different pathways
have led to new introductions, but there are definite historical
patterns to the most significant pathways. Many of the early
introductions were organisms transported on the hulls of wooden
ships. A number of introductions around the beginning of the
20th century were due to the importation and cultivation of non-native
oysters. Even though these oysters did not become established
in the estuary, the oyster shipments contained a variety of other
species that did. Most recently, the major pathway has been the
discharge of ballast water from large ships. In other aquatic
systems, additional pathways have been significant. These pathways
include the introduction of pathogens and parasites via aquaculture,
establishment of ornamental plants, and introduction of species
as bait.
Multiple impacts from a single
species-Potamocorbula amurensis
In October 1986, three small
clams were collected in San Francisco Bay by a college biology
class. They were later identified as an Asian species (Potamocorbula
amurensis) that had never before been seen on the West Coast.
Nine months later, this species had become the most abundant
clam in the northern part of the Bay, ultimately reaching densities
of nearly 50,000 clams per square meter (Peterson 1996). Other
clams were displaced and the biodiversity of bottom-dwelling
organisms was reduced (Nichols et al. 1990, Thompson 1998).
This Asian clam is also a highly
efficient filter feeder. It has been estimated that clams in
the northern portion of the Bay have the capacity to filter the
entire water column at least once and possibly more than twice
in a single day (Thompson and Luoma 1999). As a result, the clam
has virtually eliminated the annual phytoplankton blooms. Phytoplankton
are at the base of the food chain and are preyed upon by zooplankton,
which in turn are eaten by juvenile fish. There is preliminary
evidence that this cascading impact on the food chain has resulted
in a reduction in zooplankton populations.
- Andrew Cohen (San Francisco
Estuary Institute)
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