Download harmful nonindigenous species

HARMFUL NONINDIGENOUS SPECIES
INTRODUCTION
Nonindigenous species are those not native to a specific area and introduced by humans. They are sometimes
referred to as non-native species or exotic species. Some are considered pest, nuisance, harmful, or invasive species.
Schmitz and Brown (1994) refer to these species as "anthropogenic pollution."
Invasion by nonindigenous species originating from throughout the tropical-subtropical world is a major
threat to South Florida natural areas. Many nonindigenous plant and animal species have escaped cultivation and
become established in the Region. Nonindigenous plants and land animals constitute about 25% of all species in the
State as a whole (OTA 1993). Some have not only colonized disturbed sites but also invaded natural lands set aside
for preservation of natural communities and landscapes. South Florida itself probably has more problems with
aggressive nonindigenous species than any other entire State.
Economic, as well as ecologic, problems arise from invasions by nonindigenous species. Many agricultural
pests, marine fouling organisms, and aquatic weeds are nonindigenous species. Loss, through exotics infestations, of
the natural characteristics that draw visitors to South Florida from all over the world can be expected to result in
further economic losses.
Problems caused by invasive nonindigenous plant species are particularly noticeable. Florida as a whole has
approximately 925 established nonindigenous plant species growing outside of cultivation (OTA 1993). Over 100 of
these are listed as invasive in Florida by the Florida Exotic Pest Plant Council (FLEPPC 1995). Melaleuca
(Melaleucaquinquenervia) and Brazilian pepper (Schinus terebinthifolius) are well-known examples of harmful
nonindigenous trees that are widespread and expanding their coverage in South Florida. At least 23 nonindigenous
plants are now found in Florida waters (McCann et al. 1995).
Many nonindigenous animal species have become established in Florida's aquatic systems: 83 fish, at least
26 insects since 1970, 2 amphibians, 3 birds, 1 mammal, 1 reptile, 5 mollusks, 1 crustacean, and an unknown
number of pathogens (McCann et al. 1995). Many nonindigenous terrestrial animals, particularly birds, reptiles, and
amphibians, have escaped captivity and are reproducing in South Florida (McCann et al. 1995; Robertson and
Frederick 1994). Of the introduced nonindigenous bird species in the continental U.S., 63% are in Florida. Florida
also has the largest number of established nonindigenous amphibians and reptile species in the U.S. (OTA 1993).
Insects undoubtedly are the most numerous animal immigrants to Florida. At least 946 arrived without
purposeful human help, often as hitchhikers on cargo, especially plants (Frank and McCoy 1994). The best-known
problem insects are those that have caused harm to humans and economic crops. Those that harm natural systems are
less known, but could be numerous. A recent concern is the weevil Metamasius callizona, which kills all three of
Florida's native bromeliad genera (Tillandsia, Catopsis, and Guzmania) in natural areas (Frank and Thomas 1994).
This insect appears to be expanding fast, and there is concern it may soon reach the Fakahatchee Strand, an important
area for conservation of native bromeliads (J. Frank, UF, pers. comm.).
South Florida is particularly vulnerable to invasion by nonindigenous species for a variety of reasons
(Simberloff 1994), including insularity and the extent of habitat disturbance by humans. Coupled to this are South
Florida's mild, generally frost-free climate, which makes it a mecca for persons growing tropical plants and animals,
either commercially or as a hobby. Furthermore, Miami is port of entry for plants and animals arriving in the U.S.
from all over the world. Of all plant shipments into the Nation, 85% pass through Miami (Simberloff 1994).
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NONINDIGENOUS SPECIES
BACKGROUND
Description of the Problem
Nonindigenous plants negatively impact native habitats by outcompeting natives, decreasing species diversity, and
altering topography and soils. Nuisance plants significantly reduce available native habitat for several Federal
endangered species. Dense monocultures formed by melaleuca replace native vegetation and thus decrease nesting and
foraging habitats for endangered species such as the snail kite and Cape Sable seaside sparrow.
Aquatic plants such as hydrilla (Hydrillaverticillata), water lettuce (Pistia stratiotes), and water hyacinth (Eichhornia
crassipes) clog streams, rivers and lakes. These aquatic weeds create a continual problem by obstructing navigable
waterways throughout the Kissimmee-Okeechobee-Everglades system. Millions of dollars and extensive labor are
spent each year to reduce these impediments. Herbicides are frequently used to prevent clogging of waterways and
lakes. Therefore prolific nonindigenous plants are indirectly responsible for the application of tons of chemicals to
Florida waters.
Prolific animal species that have escaped to the wild may degrade habitat quality for native wildlife, introduce diseases
or pathogens, or outcompete or prey on native species. In many locations non-native herpetofauna (e.g., Anoles
segrii) have replaced native congenitors (e.g., Anoles carolinensis). Cichlid fish species have invaded ENP and appear
as dominants of the aquatic fish community in visitor areas such as the Anhinga Trail. Cichlids also are common
components of the brackish-water fish community in coastal areas of the Park adjacent to northeastern Florida Bay
(Lorenz 1993).
The escape from captivity of nonindigenous fish is a particular concern because of Florida's extensive, unique,
internationally recognized wetlands. South Florida's low natural diversity of freshwater fishes is one factor that has
made it vulnerable to invasion by nonindigenous fish. South of Lake Okeechobee, nonindigenous species already
make up over 50% of the inland fish fauna (Courtenay 1994a). Disturbance enhances establishment of nonindigenous
fish because they often are more tolerant of disrupted habitats than are native species. Because any fish species varies
morphologically and ecologically at different stages of its life cycle, nonindigenous fish can affect native fish
differently at each life stage. Invasive nonindigenous fish are a threat to native fish populations. Although there have
not yet been any known extinctions, Warren and Burr (1994) concluded that the southeastern U.S. soon will equal or
exceed the American west in the number of threatened and endangered fishes.
Non-native plant and insect pests in South Florida that attack economic crops, lawns, and golf courses have led to
widespread application of pesticides for their control. For instance, infestation of turf grass by South American mole
crickets (genus Scapteriscus) is a primary reason for the high pesticide applications on golf courses (Frank 1994).
These pesticide applications degrade water quality and cause environmental damages.
Not all nonindigenous species are harmful. Many nonindigenous ornamental plant species never escape cultivation.
Not even all species that spread beyond their planting site are invasive. In South Florida, however, the potential for
harm to natural areas from even one invasive plant species is enormous. For instance, melaleuca, introduced in the
early 1900s, now infests roughly 450,000 ac (703 mi2) of South Florida to some degree (OTA 1993). At least
50,000-60,000 ac (78-95 mi2) of melaleuca are growing as a monoculture (R. Doren, ENP, pers. comm.). Past
experience and a study on the rate of expansion indicate the uncontrolled trees could overtake most of the remaining
wetland areas south of Lake Okeechobee within 30 years (Bodle et al. 1994).
A virtually uncontrolled expansion of nonindigenous species is altering the South Florida landscape and affecting the
functioning and biological integrity of the ecosystem. Melaleuca is just one example of the many species rapidly
expanding in South Florida natural areas. Because the rate of expansion increases with time (Laroche and Ferriter
1992), it is important to control species such as melaleuca at early stages of infestation of a site. A coordinated,
integrated multispecies science program is needed to develop information and techniques to control invasions by
nonindigenous plants and animals that have already escaped cultivation and prevent introduction of new invaders. Lack
of effective control efforts at early infestation stages is a major issue.
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NONINDIGENOUS SPECIES
Existing Efforts
A comprehensive review and analysis of the effort to control harmful nonindigenous species recently was
published by OTA (1993). Many needed science topics can be gleaned from that document, which includes a special
section on Florida.
The FLEPPC is a nongovernmental group formed in 1984 to address the dilemma of invasive nonindigenous
plants in Florida. One major activity of this group has been to develop an extensive, prioritized list of harmful
nonindigenous plants. The present list includes 115 problematic nonindigenous species (FLEPPC 1995). The
FLEPPC has a research committee whose responsibilities are to determine science priorities, facilitate funding
coalitions, and review research proposals.
Progress has been made in developing effective methods for eradication of melaleuca on a local scale, and
these methods are being applied in a coordinated effort in parts of South Florida. The Melaleuca Task Force was
formed by several concerned entities that have joined together to systematically eradicate this species. As one of
several working committees of the FLEPPC, the MTF is currently investigating and implementing several control
operations and methods (MTF 1994).
Several State agencies are involved in nonindigenous plant control. The SFWMD leads several exotic
eradication efforts in South Florida. The FDOT continually reduces and selectively maintains invasive nonindigenous
plants on rights of way. The UF is conducting research on biological control of Brazilian pepper.
The FDEP has a long history of managing widespread invasive nonindigenous species on a regional basis.
Its Aquatic Plant Management Program is based on maintenance control to reduce the requirements for chemical and
other control efforts. Maintenance control, a concept that originated with the COE, is the process of maintaining a
species at or below a prescribed percentage of cover (e.g., water hyacinth at 5%) through consistent efforts (Schmitz
et al. 1993). This technique, applied to water hyacinth, substantially reduced herbicide usage and organic
sedimentation. Because of maintenance control, water hyacinths now impact only 1000-1500 ac (1.5-2.3 mi2)
annually, compared to 120,000 ac (187 mi 2) in the 1960s (D. Schmitz, FDEP, pers. comm.). Maintenance control
has also been effective with water lettuce, but not with hydrilla (Schmitz et al. 1993).
Federal agencies have many ongoing exotic control projects. The COE supports many exotic removal
programs. The NPS is involved in control of melaleuca, Brazilian pepper, Australian pine (Casuarinaequisetifolia),
shoebutton ardisia (Ardisia elliptica), and other species in the National parks and preserves. The FWS is responsible
for control of exotics in National wildlife refuges.
Local governments also have exotic removal efforts. County park and recreation agencies have concentrated
on removing invasive non-native plants from natural areas throughout South Florida. Dade County has a
multimillion dollar exotic control program to help tropical hammock areas in county parks recover from invasions by
nonindigenous plants and some prolific native vines after Hurricane Andrew.
Several Federal laws deal with importation of nonindigenous species. The Nonindigenous Aquatic Nuisance
Prevention and Control Act of 1990 and the Lacey Act authorize the FWS to issue regulations on aquatic and other
nuisance species and restrict importations of exotic species. The APHIS also has responsibilities under the Lacey Act
and administers the Federal Noxious Weed Act of 1974 and the Federal Plant Pest Act. Its responsibilities include
identification of actual or potential noxious weeds and prevention of their entry into the U.S. (OTA 1993). These
various laws as administered, however, have not been effective in preventing the importation of nonindigenous
species potentially harmful to natural ecosystems (OTA 1993).
Only a few groups are actively involved in scientific investigation of nonindigenous species that threaten
natural areas. In particular, these include the ARS, SFWMD, COE, and NPS. The SFWMD has established
herbicidal evaluation plots on several invasive plant species throughout the Region. The NPS has conducted studies
on methods to restore natural communities on rockplowed fallow farmland and prevent repeated reinvasions by
nonindigenous species after their removal (Doren et al. 1990). The COE funds research on control of aquatic weeds
and melaleuca. The ARS and UF are investigating various biological control organisms on several nonindigenous
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NONINDIGENOUS SPECIES
plants, including melaleuca and Brazilian pepper. Host-specific organisms are tested for their effectiveness as control
agents and for their general safety. The introduction of host-specific insects, such as seed and sapling eaters, can safely
and economically decrease the spread of pest plants. Predatory insects, parasites, or pathogens can be used to control
the spread of insect pests, if appropriate host-specific organisms can be found (e.g., see Frank 1994). Considerable
progress has been made on identification and testing of a biological control agent for melaleuca. The proposed ARS
quarantine facility in Fort Lauderdale will be used to expand investigations of the potential use of insects or plant
pathogens to control or reverse expansion of invasive nonindigenous plants.
The Federal Interdepartmental Committee for Management of Noxious Weeds was formed recently and is
made up of many agencies within the Departments of Interior, Transportation, Energy, and Agriculture. This group is
responsible for coordinating noxious weed management. One objective is to reorient the emphasis of control efforts
toward protecting natural lands and rangelands, not just croplands. This may eventually lead to allocation of more
research dollars to the protection of natural areas.
Publication of the OTA report (1993) on harmful nonindigenous species was a major advancement because it
provides an overview of the problem and the present institutional framework for addressing it, as well as an
evaluation of program effectiveness. Problems specific to Florida were examined in a recent report by the FDEP
(Schmitz and Brown 1994). The NPS is planning a similar report for its units.
Recently the COE (1995) completed a report that recommended the integrated use of mechanical, physical,
biological, and chemical methods to control melaleuca. The exact combination of methodologies used at a given site
will depend upon the treatment, population density of melaleuca to be removed, and status of the existing natural
system. Several combinations of methods, including that proposed by Woodall (1980), currently are under review.
MAJOR ISSUES
The major issues in South Florida related to nonindigenous species are:
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Inadequacies in funding for scientific investigations that will lead to development of effective controls.
Lack of funding to apply control methods to problem species.
Delays and lack of consistency in responses to new problems.
Scientific study on exotic species in Florida has been underfunded, considering the magnitude of the problem
and potential for further damage to the ecosystem. Most resources have been focused on agricultural pests and aquatic
weeds. Little has been spent on investigations of exotic species that threaten natural areas.
Three interrelated lines of scientific inquiry are particularly needed:
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Studies to develop control technology.
Basic biological and ecological studies to improve understanding of invasive exotic species.
Screening and risk assessment technology.
With respect to control technology development, biological controls must be identified, tested, and
distributed; environmental controls must be hypothesized and examined; mechanical or manual removal and herbicidal
application strategies must be designed and applied and results of applications tested; and habitat restoration strategies
must be treated as experiments in which follow-up data are collected and analyzed. Basic biological and ecological
investigation is essential to the overall control effort. Such efforts will not only help develop greater understanding
and perspective but also help design details of control methods; e.g., which biocontrol agents would be most
effective, when to apply herbicides for maximum effectiveness. Screening and risk assessment technology could help
focus control efforts on the greatest potential problems. All three lines of investigation are vitally important to the
South Florida Ecosystem Restoration effort.
Biological control is a well-developed science. The simplest definition, paraphrased from Center et al.
(1994), is "the introduction of a pest's own natural enemies (parasitoid, predator, or pathogen) from the pest's native
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NONINDIGENOUS SPECIES
environment to a new environment in which the pest has become established." Biocontrol has been successfully
applied to control of agricultural pests and aquatic weeds throughout the U.S. and in other parts of the world (Center
et al. 1994). Recent successes include control of alligator weed in the southeastern U.S., including Florida. There is
an extensive protocol to ensure a selected control agent will not only be effective against the chosen target but also
will not affect nontarget organisms in the new environment. Biologic control is the possible means of control in
certain cases (e.g., to control the Mexican weevil attacking native bromeliads (Frank and Thomas 1994).
Investigation of biological control, although it has made promising progress on several major invaders of
South Florida natural areas, is inadequately funded, and other control methods alone cannot alone halt or reverse
region-wide invasions. Biocontrol is an essential component of the control of melaleuca, Brazilian pepper, and other
plant species already widespread in South Florida natural areas. Construction of the quarantine facility at Fort
Lauderdale, an essential component of the ARS biological control program, is not yet fully funded nor are the staff
and resources to operate the facility.
The limited amount of biological and ecological information concerning invasive species affects the ability
to generate funding or devise control strategies. Scientific efforts are needed to address the following questions:
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How will water management alterations to restore the natural ecosystem affect nonindigenous plants and
animals?
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What are the principal controls on expansion of an invasive nonindigenous species in its place of origin?
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What are the impacts of nonindigenous species on native species and ecosystems?
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What are the major factors influencing expansion rates of specific problem species in South Florida?
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What are the conditions that cause greatest stress to the invasive species at various life stages?
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What factors make a natural area susceptible to invasion by nonindigenous species?
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What are the seasonality of flowering, fruiting, and germination, as well as responses to environmental
variables, that might allow a nonindigenous species to be controlled by management measures such as new water
management or prescribed burning practices?
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How do nonindigenous plant species that establish monospecific stands affect the water budget? For
instance, does melaleuca consume more water, particularly during the dry season, than the native species it replaces?
Addressing such questions would not only provide greater understanding for the need to control a species but would
also provide insight to help design biological and environmental controls.
Science-based screening and risk assessment methods concerning invasive nonindigenous species are lacking,
but they are needed to prioritize species so the greatest threats receive the most attention. Risk assessment methods
would help focus control efforts by pinpointing generic invasive characteristics that could be used to screen proposed
introductions and exclude those with high invasive potential. This would provide a scientific basis for banning the
import of certain species before they become a problem rather than after.
Habitat restoration strategies are needed to prevent invasive nonindigenous plants from returning once they
are removed from heavily infested areas. One general strategy is to replant native vegetation, but scientifically
supported guidelines on how to most effectively reestablish native plant communities in South Florida are limited.
Horticultural approaches to control of nonindigenous species are poorly explored. The development and
widespread dissemination of sterile varieties of popular, but invasive or potentially invasive, nonindigenous species
might prevent future invasions by such species. Sterile cultivars are very popular in other regions; e.g., cottonless
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NONINDIGENOUS SPECIES
cottonwood trees, fruitless mulberry trees, and podless locust trees in the Southwest. The feasibility and potential
long-term benefits of developing sterile cultivars is worth investigating.
In addition to their harmful effects on natural areas, many invasive nonindigenous species also are
detrimental to agricultural lands. For instance tropical soda apple (Solanum viarum), a threat to natural areas, is
becoming a serious agricultural problem in Florida. Even if controlled on agricultural lands, it will continue to
reinvade unless infestations in natural areas also are curtailed. One recent immigrant, the weevil Metamasius
callizona, that is threatening the survival of native Florida bromeliads, also attacks ornamental bromeliads and
pineapple (Frank and Thomas 1994).
The role of nonindigenous animals in South Florida natural areas is so poorly documented that it is difficult
to design and mount an effective effort to control those that are harmful to native plant and animal communities. The
major issue, therefore, is the lack of meaningful information concerning the effect of nonindigenous animals on
Florida's native ecosystems.
INFORMATION NEEDS
The information needs critical to control of nonindigenous species are shown in Figure 4 as related to the
restoration and scientific objectives. The recommended approach includes the following:
> Prepare coordinated science programs on invasive or otherwise harmful nonindigenous species
for inclusion in the separate multispecies management plans for plants and animals recommended
by the South Florida Ecosystem Restoration Interagency Working Group (1994).
The first step in development of each science plan should be to prepare a comprehensive review of recent and
ongoing studies. State agencies, particularly the FDEP and SFWMD, should be involved in the process, as should
FLEPPC. The programs should take a long-term view toward the problem of invasive nonindigenous species in South
Florida and consider the problem in the context of the South Florida Restoration effort. Efforts should not be restricted to
only studies of individual species, but rather should attempt to build a set of principles that helps support a holistic,
ecosystem approach to exotics control. The questions listed under Major Issues above should be addressed.
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Continue and expand investigations of biological control. (Suggested lead--ARS, COE)
These must include:
·
·
·
·
·
·
Foreign exploration - search for the most effective control species in the species' native land.
Overseas screening process - determine the most effective and safest species before importing to the U.S.
Quarantine follow up - clearance for field release.
Onsite field sites - colonization in areas affected.
Assessment of success and performance of introduced control species.
Technology transfer - distribution of organism throughout range of invasive species.
The quarantine facilities in Fort Lauderdale and Gainesville are critical components of the biological control
effort. Funding must be provided to construct and operate the quarantine facility at Fort Lauderdale, improve and
maintain the quarantine facilities in Gainesville, and provide support personnel for the Fort Lauderdale facility. Priority
in biological control studies should be given to the greatest threats.
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Conduct studies
(Suggested lead--NBS)
to
develop
ecological
understanding
of
invasive
nonindigenous
species.
With respect to nonindigenous plants, more work is needed to determine:
·
·
Factors that affect invasibility of natural areas.
Environmental requirements and phenology of each problem species as these relate to their vulnerability
to specific prescribed burning or water management regimes.
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Planting approaches
that lead to
establishment of
native ecosystems
with low invasibility.
Planting approaches
that discourage
reinvasion by
exotics.
Develop effective
restoration
methods that
discourage
reinvasion by
exotics.
Interactions with
native species.
Relationships with
hydropattern and
fire.
Autecology of
various exotics in
South Florida.
Determine and
enhance natural
controls.
Effect of potential
non-native control
agents on native
species.
Environmental
relationships in land
of origin.
Controlling insects/
pathogens in land of
origin.
Autecology in land
of origin.
Develop
biological controls.
Distributions of
exotics in the wild.
Develop
multispecies
monitoring plan.
Effects of exotics
on recovery of
native ecosystems
from natural
disturbances.
Impacts, by
species, on native
ecosystems.
Effective
control methods.
Common
characteristics
of invasive exotics.
Environmental
requirements and
phenology of problem
species.
Factors that
affect invasibility
of natural areas.
Criteria for
determining
greatest threats and
documenting
problem species.
Documentation of
problem species.
Develop
multispecies
management
plan.
Protect natural ecosystems from
invasive exotic species.
Status of exotics in
natural
communities.
Halt and reverse spread of
invasive naturalized exotics.
Figure 4. Goal, objectives, and information needs for efforts on
INFORMATION
NEEDS
SCIENCE
OBJECTIVES
RESTORATION
OBJECTIVES
RESTORATION
GOAL
HARMFUL NONINDIGENOUS SPECIES
Technical
approaches
to assessing
risk at entry,
distribution,
escape,
early invasion
stages.
Develop
screening
and risk
assessment
methods.
Horticultural
experiments
to create
podless or
seedless
cultivars.
Develop
sterile cultivars
of
popular exotics
that
regenerate
readily in
South Florida.
Prevent invasions by
new exotic species.
NONINDIGENOUS SPECIES
·
·
·
·
Common characteristics of invasive non-native species in Florida.
Effects of nonindigenous plant infestations on native species and the environment.
Effective habitat restoration strategies to prevent reinvasion by nonindigenous species after their
removal.
Recommendations for implementing integrated pest management strategies.
With respect to nonindigenous animals, scientific study is needed on impacts of these species on food webs,
community structure, and populations of species in natural areas in which they have become established. For some
taxa, such as insects, even more basic information is needed. Lacking, for instance, is an inventory of insect species
(natives as well as known exotics) in South Florida.
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Develop scientifically based methods for
efforts to control invasions relatively early
colonization). (Suggested leads--ARS, NBS, FGFWFC)
screening
in the
and risk assessment to prioritize
process (importation, distribution,
Needed are effective criteria to identify and screen potentially invasive or otherwise harmful nonindigenous
plants and animals before they become well established here or preferably even before they enter the U.S. Science
activities should be integrated with prevention and eradication efforts.
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Develop
FWS, NPS)
a
multispecies
monitoring
plan
for
nonindigenous
plants. (Suggested Leads--NBS,
As part of plan development, existing monitoring programs should be inventoried and analyses made to
determine overlaps and gaps in coverage. The plans should ensure that basic variables are defined and measured the same
way so that data can be analyzed across areas, not just locally. Activities of the COVER Group should be supported
and their efforts incorporated into the plant plan. A computerized atlas of ongoing monitoring programs should be
prepared. The FDEP, SFWMD, FLEPPC, and county natural resource agencies should be major partners in plan
development.
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Develop
FWS, NPS)
a
multispecies
monitoring
plan
for
nonindigenous
animals. (Suggested Leads--NBS,
Systematic monitoring of probable points of entry of nonindigenous species (Courtenay 1994b) should be a
major provision of the animal plan. This is particularly important for fishes, because, once a nonindigenous fish
extends its range beyond the point of introduction, eradication becomes impossible and control costs soar to prohibitive
levels (Courtenay 1994a). A monitoring program is needed that can detect new introductions early enough for
eradication efforts to be made before control is out of the question. The FDEP, FGFWFC, and county natural resource
agencies should be major partners in plan development.
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Prepare a prioritized list of nonindigenous plant species currently and potentially the
greatest threats to natural areas. Suggest target areas and species for expanded control efforts.
Start with the list prepared by the FLEPPC. Use information from the recommended survey and available
monitoring results. Develop information on a plant community basis (i.e., pineland, hammock, beach, etc.).
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Prepare a prioritized list of nonindigenous animal species currently and potentially the
greatest threats to natural areas or native plant or animal populations.
>
Based on information from the above studies, generate brochures and news releases that
describe the nonindigenous species problem in South Florida to land managers, decision
makers, and the public.
A public information effort based on scientific information will help develop a greater awareness of the
problem and its present and potential impacts on natural areas. Once informed of their contributions to such problems,
a concerned public often will change its habits.
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NONINDIGENOUS SPECIES
>
Conduct horticultural investigations to develop sterile cultivars of popular and widely
used, but invasive, non-native ornamental plants, such as certain flowering trees and Ficus
species. (Suggested Lead--USDA)
This technology is being used elsewhere for aesthetic reasons. For instance, fruitless mulberry trees, podless
locust trees, and cottonless cottonwood trees are very popular nursery items in the southwestern United States. The
Hong Kong orchid tree (Bauhiniavariegata), a popular ornamental plant in South Florida, is a local example. Species
such as royal poinciana, Surinam cherry (Eugenia uniflora), the exotic Scaevola, and the many ornamental Ficus trees
would be good candidates for this treatment. Development of sterile cultivars of non-natives with invasive tendencies
could provide long-term benefits to natural areas. The FLEPPC list should be used to select non-native trees and shrubs
whose propagation outside of cultivation should be controlled.
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Encourage cultivation and use of native species in landscaping with special promotions
to "introduce" promising native species to growers and the public.
Over 100 tree species alone are native to South Florida, most growing nowhere else in the continental U.S.
They are adapted to South Florida's soils and climate, and many are appropriate for landscaping. Greater use of native
species in landscaping will reduce the probability of invasions by nonindigenous species.
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Encourage the expansion into Southeast Florida of commercial operations that produce
landscape mulch from melaleuca and other pest plants.
At least two companies currently produce melaleuca mulch, but they do not appear to be operating on the East
Coast of South Florida.
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Encourage development and use of biological controls in place of pesticides to control
pest species.
Particularly with respect to large-scale, repeated applications, use of biological controls instead of pesticides
has enormous potential to reduce damaging environmental impacts often associated with efforts to control exotics in
managed areas such as agricultural fields, golf courses, and lawns.
BIBLIOGRAPHY
Bodle, M.J., A.P. Ferriter, and D.D. Thayer. 1994. The biology, distribution, and ecological consequences of
Melaleuca quinquenervia in the Everglades. Pages 341-355 in S.M. Davis and J.C. Ogden, editors. Everglades:
The Ecosystem and Its Restoration. St. Lucie Press, Daytona Beach, Florida.
Center, T.D., J.H. Frank, and A. Dray Jr. 1994. The biological control of invasive non-indigenous species in Florida.
Pages 209-214 in D.C. Schmitz and T.C. Brown, editors. An Assessment of Invasive Non-indigenous
Species in Florida's Public Lands. Technical Report No. TSS-94-100. Bureau of Aquatic Plant Management,
Division of Environmental Resources Permitting, FDEP, Tallahassee, Florida.
Courtenay, W.R. Jr. 1994a. Non-indigenous fishes in Florida. Pages 57-63 in D.C. Schmitz and T.C. Brown, editors.
An Assessment of Invasive Non-indigenous Species in Florida's Public Lands. Technical Report No. TSS-94100. Bureau of Aquatic Plant Management, Division of Environmental Resources Permitting, FDEP,
Tallahassee, Florida.
Courtenay, W.R. Jr. 1994b. Current major pathways of fish introductions. Pages 64-66 in D.C. Schmitz and T.C.
Brown, editors. An Assessment of Invasive Non-indigenous Species in Florida's Public Lands. Technical
Report No. TSS-94-100. Bureau of Aquatic Plant Management, Division of Environmental Resources
Permitting, FDEP, Tallahassee, Florida.
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NONINDIGENOUS SPECIES
Doren, R.F., L.D. Whiteaker, G. Molnar, and D. Sylvia. 1990. Restoration of former wetlands within the Hole-in-theDonut in Everglades National Park. Proceedings of the Seventeenth Annual Conference on Wetlands
Restoration and Creation. Hillsborough Community College, Plant City, Florida.
Florida Exotic Pest Plant Council. 1995. Exotic Pest Plant Council's 1995 list of Florida's most invasive species.
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