Download The Impact of Invasive Species and the Role of Legislation in their

The Impact of Invasive Species and the Role of Legislation in
their Control in the United States of America
Allison Rangolan
Coastal Policy Class
Dr. Steffen Schmidt
Fall 2003
©2003, Do not use without author’s permission
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The Impact of Invasive Species and the Role of Legislation in their Control in the
United States of America
Introduction
Biodiversity
The most widely used definition of biological diversity considers three levels: genetic,
species and ecosystem (Norse, 1993). Genetic diversity refers to the different genes
possessed by individuals of the same species. These differences may confer different
adaptations under a variety of environmental conditions and increase the chances of
survival of the species under adverse stochastic conditions. Species diversity is the
number of species at a location and can vary greatly. Ecosystem diversity refers to the
different physical environments and variable biological composition of species within a
community of organisms.
Biodiversity is important for a variety of reasons. Marine biodiversity provides essential
products (food, medicines, and raw materials). These are the benefits which are generally
acknowledged by society, those that produce tangible benefits. However, biodiversity is
also responsible for a range of ecosystem services. Mangrove forests protect the coast
from storm surges and waves. Coral reefs decrease the wave energy of incoming waves
that would otherwise cause coastal erosion. Mangrove roots and seagrass beds reduce the
suspended sediment in the water column that would otherwise inhibit photosynthesis by
benthic primary producers. Biodiversity is also recreationally and aesthetically valuable
and has an intrinsic value (Norse, 1993).
In recent years introduced species and their impact on the environment have become
more recognized. Following habitat destruction, introduced species are considered the
greatest cause of the loss of marine biodiversity (Carlton, 2001). According to the
Environmental Protection Agency (EPA), invasive species are also second to habitat
destruction as a threat to endangered species (Cangelosi, 2003). The EPA estimates the
annual economic cost of the damage in the United States to be $100 billion (Cangelosi,
2003).
Introduced Species
Introduced species are referred to by a range of terms: biological invaders (bioinvasives),
biological pollutants, alien, non-indigenous or invasive species, exotics (Norse, 1993).
Invasive species refers to a “broadly defined group of introduced species that bring or
could bring some measure of harm.”
(http://www.pewoceans.org/reports/introduced_species.pdf).
According to Executive Order 13112 (1999), an invasive species is “an alien species
whose introduction does or is likely to cause economic or environmental harm or harm to
human health (Carlton, 2001).” An introduced species is able to:
1. colonize a new area where it did not previously occur
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2. expand its range by direct or indirect human activity
3. exist with geographical discontinuity between native and new areas
4. exist in self-sustaining populations without human assistance (Boudouresque and
Verlaque, 2002).
Although invasive species may have no apparent effect or be viewed as positive additions
to recipient ecosystems (Norse. 1993), many tend to either replace keystone species or
have a strong negative impact on them within ecosystems being colonized
(Boudouresque and Verlaque, 2002).
Bioinvasions may occur accidentally or be carried out intentionally. According to Norse
(1993), although invasions have always occurred as a part of natural historical, the type
and scope of human-mediated invasions is very different with numerous species being
rapidly transported. Introductions occur by means of vector transport. Vectors may
include ships, drilling platforms, dry docks, navigation buoys and marina floats, canals,
aquaria, and fisheries and recreational activities (Carlton, 2001).
Invasive species are problematic because they may possess predatory, competitive,
parasitic and defensive strategies with which native biota has had no prior experience.
Populations of the recipient ecosystems are therefore susceptible to displacement by these
alien species. Additionally, the invading organisms may benefit from having no
predators, parasites, or diseases in the new region to limit population growth (Norse,
1993). Introductions alter species interactions, nutrient cycling and energy flow which
affect entire communities (Carlton, 2001).
Some of the more recent and better-known bioinvasions include the European shore crab
(Carcinus maenus), the Chinese mitten crab (Erichocheir sinensis), the Pacific spotted
jellyfish (Phyllorhiza punctata), the Asian whelk (Rapana venosa), the Zebra mussel
(Dreissena polymorpha), the Pacific Sea Star (Asterias amurensis), the Asian kelp
(Undaria pinnatifida) and the Mediterranean green seaweed (Caulerpa taxifolia)
(http://issg.appfa.auckland.ac.nz/database/welcome/;
http://www.pewoceans.org/reports/introduced_species.pdf).
Case Study: Caulerpa taxifolia
Caulerpa taxifolia is a marine alga. It was originally widely distributed throughout
tropical seas and is native to Brazil, Venezuela, Colombia, Costa Rica, Antilles, Gulf of
Guinea, Red Sea, Somalia, Kenya, Tanzania, Madagascar, Maldives, Seychelles,
Pakistan, India, Sri Lanka, Bangladesh, Malaysia, Indonesia, Philippines, Vietnam,
China, Japan, Hawaii, Fiji, New Caledonia, and Northern Australia
(http://issg.appfa.auckland.ac.nz/database/welcome/). Although traditionally a tropical
species, in 1980 a clone was discovered in a Stuttgart aquarium which was able to live in
colder water (Gili, 2000), and the species was subsequently introduced to the
Mediterranean and is now found in Monaco, France, Italy, Spain, Croatia and Tunisia. It
was most recently discovered in the Pacific and Atlantic Oceans, in East Australia, and in
the summer of 2000, off southern California and southern Florida
(http://issg.appfa.auckland.ac.nz/database/welcome/). The strain off the coast of
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California was analyzed genetically and confirmed to be the Mediterranean, not the
tropical, strain of the alga (Jousson et al, 2000).
Internationally, the aquarium trade has been identified as the primary means of dispersal.
It is believed that it was initially introduced to the Mediterranean as waste from the
Monaco Aquarium. Fishing and boating activities have also been implicated in the spread
of the species (http://issg.appfa.auckland.ac.nz/database/welcome/).
What characteristics make Caulerpa taxifolia a successful invasive?
Two of the primary reasons identified for the success of C. taxifolia are its mode of
reproduction (Boudouresque and Verlaque, 2002) and the production of defensive
secondary metabolites (Lemee et al, 1997; Boudouresque and Verlaque, 2002). Although
sexual reproduction is known, only vegetative reproduction has been observed in the
Mediterranean. Vegetative reproduction is attained from cuts of both stolons and
branches. There is no resting stage. Colonization by fragmentation therefore occurs
readily.
Experimental results on the toxicity of secondary metabolites from C. taxifolia indicate
that they inhibit the proliferation of some phytoplanktonic algae. Caulerpenyne is the
main product and appears to reduce photosynthetic activity within cells (Lemee et al,
1997). It diffuses into the water and is then degraded to produce more toxic compounds
(http://issg.appfa.auckland.ac.nz/database/welcome/). Ecologically, the metabolites
endow C. taxifolia with a competitive advantage over the native flora (Lemee et al, 1997)
and the species also experiences little or no predation (Boudouresque and Verlaque,
2002).
What impact has it had on native species?
Caulerpa taxifolia ranges from the surface to depths of 100m and colonizes a variety of
substrata. According to Madl and Yip (2003), a decrease in the mean species richness,
density, biomass and composition of fish assemblages and in the diversity and abundance
of motile invertebrates has been recorded in areas dominated by C. taxifolia.
The alga reduces the light penetrating to the benthos and its rhizoids trap and chemically
alter sediment killing the native flora and allowing it to effectively invade areas
traditionally occupied by native alga and seagrasses. These grasses (especially Posidonia
oceanica in the Mediterranean) are important primary producers, provide refuge, habitat,
spawning and nursery grounds for a variety of organisms and protect the coastline. Their
elimination reduces the productivity of the ecosystem and the number of organisms it can
support and increases the susceptibility of the coastline to destruction. There are therefore
both ecological and economic implications (Madl and Yip, 2003).
Invertebrates are also affected. C. taxifolia suffocates some gorgonian species. However,
probably more importantly, it outcompetes the usual primary producers within systems,
reducing the food supply available to herbivores notably Lytechinus variegatus and Sarpa
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salpa. The endotoxins produced by the alga therefore disrupt the entire food web,
changing the food supply. Concentration of the toxins within the food chain has actually
led to incidents of human food poisoning from consumption of the Mediterranean bream,
Sarpa salpa (Madl and Yip, 2003).
According to Madl and Yip (2003), in addition to changing the food supply, C. taxifolia
may alter the composition of fish assemblages by changing the predation pressure
experienced by species with certain color patterns. Traditionally cryptic areas may no
longer provide the camouflage needed by some species or color morphs and these
organisms will relocate to avoid predators.
Entire ecosystems are altered by the alga. The ecological devastation often has economic
impacts. It affects fisheries by changing the species composition and abundance. The
fishing community has to expend greater effort to catch target species. Some of the fish
caught will be unfit for human consumption because of the high concentrations of
accumulated toxins. Tourism may also be negatively affected. Dive and snorkel sites will
be less diverse, have less aesthetic appeal and the number of people participating in these
activities may be reduced. Similarly, the recreational and aesthetic value of some areas
will decrease because of the loss of biodiversity. The negative effects can be extensive.
How have the threats been addressed?
Prevention is best but because it may not always be possible, eradication sometimes
becomes necessary as was the case with C. taxifolia. Complete removal of organisms
may be feasible in the initial stages of invasion. Control and containment may be more
practical than complete removal for established invasive populations. Chemical,
mechanical, biological and ecological control may be employed. Toxic chemicals can be
used to remove species but concerns arise from possible impact on non-target organisms
and humans. Mechanical control involves physically removing the invaders. It is often
successful but can be labor intensive and expensive. Biological control refers to
introduction of natural predators, parasites or diseases from the invaders native region.
This method is potentially inexpensive and environmentally sound. However, the control
organisms may not survive in their new environment or they may themselves become
invasive (http://www.esa.org/education/edupdfs/invasion.pdf). Ecological control is the
modification of a physical or chemical parameter to affect the target species or to enhance
conditions for a biological control organism (Carlton, 2001). These methods may
therefore be used in isolation or in concert with each other.
Once C. taxifolia has become established, for example, control and elimination is
extremely difficult. As with most other invasive species, prevention is the best way to
avoid potential harm because eradication is not only costly but also largely unsuccessful.
Preventive measures suggested by Madl and Yip (2003) include:
 proper disposal of water and other materials from aquaria and using alternative
species of seaweed and
 checking and appropriate cleaning of fishing gear, anchors, trailers and rudders
especially after mooring in contaminated areas.
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Manual uprooting has been attempted in some areas (France and Spain). However, this is
not generally successful and is only feasible for small patches of the alga. The procedure
usually has to be repeated periodically (France has performed uprooting exercises
annually in the Port-Cros national park since 1994) and the danger of unintentional
dispersal of the species by release of fragments is a concern (Madl and Yip, 2003).
Physico-chemical methods involving chemical treatments, vacuuming, suction pumps,
dry ice, and hot water jets have been employed with varying levels of success. Copper
and chlorine are two of the most commonly chemicals used in eradication attempts. Both
are toxic to entire ecosystems. Chlorine was used in California and initial results
indicated possible success. The treatment was initiated comparatively quickly once the
strain was identified and the apparent success of the project has been at least partially
attributed to this fact (Withgott, 2002). Traditional algaecides have proven ineffective at
eliminating C. taxifolia (Madl and Yip, 2003).
Some scientists now feel that biological control may be the best option for eradication or
containment of C. taxifolia. Since 1994, four mollusks (ascoglassans) have been
identified as potential biocontrol agents: Oxynoe olivacea, O. azuropunctata, Lobiger
serradifalci and Elysia subornata. They puncture the algal cell wall and imbibe some of
the algal contents. However, all four species are either unable to reproduce or function at
the low temperatures of the Mediterranean. Additionally, L. serradifalci pierces holes in
the cell wall of the alga, weakening the plant and increasing the likelihood of
fragmentation and dispersal (Madl and Yip, 2003).
There are also other concerns associated with the proposed use of biocontrol agents
(Madl and Yip, 2003):
 preying on non-target species
 introduction of pathogens
 competition with indigenous Mediterranean ascoglassan species (E. subornata is a
tropical species)
 dispersal throughout the Mediterranean region.
Governments and environmental agencies are somewhat reluctant to embark on this
project because of the potential for negative repercussions (Madl and Yip, 2003).
However, if extensive experimental data indicate that the likelihood of inducing more
damage on the ecosystems by introducing the ascoglassans is minimal, then the project
should proceed. Other techniques have been less successful in eliminating established
populations of C. taxifolia than hoped and this appears to be the most promising option.
A 1993 French decree banned the offering, sale, buying, use and dumping into the sea of
C. taxifolia. The collection and transport of the algae are also subject to a system of
authorization. In Australia, an import ban was implemented in 1996. It was listed as a
Noxious Species by the parliament of New South Wales in 2000 and cannot be bought,
sold, traded of kept in an aquarium in New South Wales. In 2001 in the United States of
America, the governor of California was signed a bill prohibiting the possession, sale and
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transport of C. taxifolia throughout California. Under the federal Noxious Weed and
Plant Protection Acts (1999 and 2003 respectively) the importation, interstate sale and
transport of the Mediterranean strain are prohibited (Madl and Yip, 2003).
Legislation
Preventing the establishment of undesirable invasive species is the best, most cost
effective method of management. Legislation is necessary for this to be successful. The
Convention on Biological Diversity (CBD) was signed in 1992 at the 1992 United
Nations Conference on Environment and Development (UNCED) in Rio de Janeiro and
ratified in 1993 (http://www.unep.ch/seas/main/legal/lcbd.html). It represents one of the
major international agreements which addresses the issues associated with introduced
species. Eradication, control, mitigation of invasive species and their impacts combined
with legislation and guidelines at national, regional and international levels are some of
the ways that the Convention on Biological Diversity (CBD) is addressing the issue of
invasive species. Paragraph h of Article 8 (In-situ conservation) of the Convention notes
that "Each Contracting Party shall, as far as possible and as appropriate, ….prevent the
introduction of, control or eradicate those alien species which threaten ecosystems,
habitats or species;…” (http://earthwatch.unep.net/biodiversity/invasivespecies.php).
Internationally, the United Nations International Maritime Organization (IMO) instituted
voluntary ballast water exchange (BWE) guidelines in 1991. Ships were to exchange
their ballast water in the open ocean to reduce the number of organisms transported
between ports. However, for a number of reasons this only met with limited success:
certain factors prevent ships from undertaking BWE, organisms attached to the base and
the walls of ballast tanks may remain attached following exchange, and the design of the
tanks may prevent complete BWE (Carlton, 2001).
There are a number of legislative instruments specific to the United States of America
(U.S.A.) which address the issue of invasive species to varying extents; some concentrate
specifically on invasive species while others include bioinvasives in subsections. On
November 29, 1990, the U.S. Congress passed the Nonindigenous Aquatic Nuisance
Prevention and Control Act (NANPCA). The purposes of the Act were “to prevent
unintentional introduction and dispersal of nonindigenous species into U.S. waters via
ballast water management and other requirements; to coordinate federally conducted,
funded or authorized research, prevention control, information dissemination and other
activities regarding the zebra mussel and other aquatic nuisance species; to develop and
implement environmentally sound control methods to prevent, monitor and control
unintentional introductions of nonindigenous species from pathways other than ballast
water exchange; to understand and minimize economic and ecological impacts of
nonindigenous aquatic nuisance species that become established, including the zebra
mussel; and to establish a program of research and technology development and
assistance to States in the management and removal of zebra mussels
(http://www.anstaskforce.gov/nanpca.htm).”
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In 1996, Congress reauthorized the original act as the National Invasive Species Act
(NISA). The BWE guidelines in these acts were similar to those set out by the IMO for
ships entering U.S ports from areas beyond the exclusive economic zone (EEZ). In June
2002, the U.S. Coast Guard announced that it intended to make compliance compulsory
at a later date because of the low level of participation (Cangelosi, 2003). The Act
includes a number of additional findings, including that once introduced, aquatic
nuisance species are unintentionally transported and introduced into inland lakes and
rivers by recreational boaters, commercial barge traffic and other pathways. It stresses
the need for preventative management measures nationwide to prevent the further
introduction and infestation of destructive species. The findings state that nonindigenous
species may compete with or prey upon native species of plants, fish, and wildlife, carry
diseases or parasites that affect native species, and/or disrupt the aquatic environment and
economy of affected nearshore area. The Act reauthorizes and modifies a number of the
ballast management programs and provisions identified in the Nonindigenous Aquatic
Nuisance Prevention Control Act of 1990, and directs establishment of record keeping
and reporting procedures and sampling techniques, and monitoring for compliance with
guidelines
(http://www.csc.noaa.gov/cmfp/reference/National_Invasive_Species_Act_1996.htm).
Despite some level of success, Carlton (2001) cited the two major obstacles that limited
the success of NISA as the lack of adequate funding and a strong programmatic structure.
On February 3, 1999, President William J. Clinton, issued Executive Order 13112
regarding invasive species. The order clearly stated the duties of federal agencies,
established an Invasive Species Council defining its structure and duties, and detailed the
considerations to be incorporated in an Invasive Species Management Plan
(http://www.nepa.noaa.gov/eo13112.pdf). Federal agencies under section 2 of the
Executive Order are directed to 1) prevent the introduction of such species; 2) control
populations of such species, and; 3) provide for restoration of native species and habitat
conditions in ecosystems that have been invaded
(http://ccpr.freedom.org/invasive/eo13112.html). The aim of the National Invasive
Species Council (NISC) which was established was focusing attention on the scale of
introductions and the need for management (Carlton, 2001).
In September of 2002 the National Aquatic Invasive Species Act (NAISA) was
introduced. It was reintroduced in 2003. The NAISA aims to correct certain problems
identified in previous legislation. Past attempts at reducing species introductions from
ships have yielded limited success. According to the new act the BWE will remain
optional until 2011 at the latest, after which BWE and other treatment options will be
required to meet an established standard (Cangelosi, 2003). NAISA also aims to do the
following: Screen live aquatic organisms to prevent undesirable introductions, conduct
ecological surveys to allow early detection of invasive species and analysis of rates and
patterns of invasion, collect and disseminate information on bioinvasives through a
database, establishing federal funding and resources for rapid response to introductions,
developing State management plans, preventing interbasin transfer of organisms by
barrier projects, educating recreational boaters on proper cleaning of their boats to reduce
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transfers of species between water bodies, and conducting further research on invasion
pathways, treatments and prevention (Pimentel, 1999).
Other existing legislation such as the Lacey Act (1900) and the Federal Noxious Weed
Act (1974) also regulate some invasive species to some extent.
Discussion
More emphasis is being placed on the importance of invasive species and their effects
within ecosystems both in the United States and globally than previously. Internationally
a greater effort must be made to preserve biodiversity and prevent the introduction and
establishment of ecologically and environmentally debilitating species. National efforts
are necessary but like so many other issues affecting the international community,
globalization necessitates that each nation contribute knowledge and personnel to this
cause. Many countries have not signed the CBD or, after signing it have failed to ratify it
(the U.S.A. is one such nation only having signed the convention on June 4, 1993; CicinSain and Knecht, 2000). Additional research, more stringent regulations and larger task
forces of trained personnel are required to reduce the number of potentially devastating
introductions that occur. A comprehensive list of species that have proven invasive
should be compiled and made globally available to help prevent the spread of known
threats.
Despite attempts to regulate the transportation of and therefore the risk of invasion, some
countries are still not cognizant of the potential danger that introduced species pose to
biodiversity and fail to act accordingly to prevent their introduction or establishment in
their territorial waters. Governments must realize that the threat presented by invasive
species is a real one. French scientist Alexandre Meinesz noticed small patch of C.
taxifolia off the waters of the Monaco aquarium in 1989, and alerted the government of
the need for immediate action. Two years elapsed before they reacted, by which time the
alga had firmly established itself (Kaiser, 2000). The challenge is to prevent additional
invasions but this will be possible only if each nation monitors its territorial waters and
potential vectors within them.
When the NANPCA was enacted, Congress recognized the limitations of BWE and
incorporated the possibility of alternative treatment for that reason. However, the absence
of quantitative standards has made ship owners reluctant to implement treatment
alternatives such as ozone, ultraviolet radiation, filtration, heat, chemical biocides and
deoxygenation. A report of the Ballast Water and Shipping Committee to the Aquatic
Nuisance Species Task Force found that BWE effectiveness ranged from 39 to 99.9
percent depending on the taxonomic groups and ships studied. NAISA legislation
established 95 percent death or removal of vertebrates, invertebrates, phytoplankton and
larger forms of algae as acceptable and the act provides incentives for adoption of ballast
water treatment (Cangelosi, 2003).
Coastal shipping was exempted from ballast rules because the only approved treatment,
BWE, could only be performed in the open ocean where these vessels did not venture.
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NAISA requires even coastal vessels to maintain records of ballast operations and
provides the abovementioned incentives for adoption of treatment alternatives to vessels
making coastal voyages (Cangelosi, 2003). These and other amendments and corrections
have been made gradually but they indicate a progressively better understanding of the
biology and impacts of bioinvasives by scientists, recognition by policy makers of the
need to reduce the potential risks to the greatest extent possible and closer interaction
between researchers and politicians.
Once these instruments have been agreed upon, they must be enforced. Shortly after the
ban was instituted in California, inspectors in San Francisco allowed a shipment
containing “Caulerpa species” to enter the state because they were unable to identify it to
the required level (Withgott, 2002). It is important to have trained personnel at ports of
entry to identify species and prevent the entry of black-listed exotics. As Boudouresque
and Verlaque (2002) suggested, it may become necessary instead to produce a “clean list”
of species that can be imported.
Enactment and enforcement of legislation nationally, regionally and globally, monitoring
of its success and continuous review to correct any shortcomings and oversights is the
only way to combat the threats presented by introduced species.
References
Boudouresque, C., Verlaque, M. (2002). Biological pollution in the Mediterranean Sea:
invasive versus introduced macrophytes. Marine Pollution Bulletin, 4, 32-38.
Cangelosi, A. (2003). Blocking invasive aquatic species. Issues in Science and
Technology Online, Winter 2002-03, 69-74.
http://www.nap.edu/issues/19.2/cangelosi.htm
Carlton, J (2001). Introduced species in US coastal waters. PEWS Ocean Commission.
http://www.pewoceans.org/reports/introduced_species.pdf
Cicin-Sain, B., Knecht, R. (2000) The future of U.S. ocean policy. Washington, D.C.:
Island Press. p. 257.
Gili, J. (2000). Frontline view of an invasion. Science, 287, 1762.
Jousson, O., Pawlowski, J., Zaninetti, L., Zechman, et al. (2000). Invasive alga reaches
California. Nature, 408, 157-158.
Kaiser, J. (2000). California algae may be feared European species. Science, 289, 222.
Lemee, R., Pesando, D., Issanchou, C., Amade, P. (1997). Microalgae: a model to
investigate the ecotoxicity of the green alga Caulerpa taxifolia from the Mediterranean
Sea. Marine Environmental Research, 44, 13-25.
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Pimentel, D., et al. (1999). Environmental and economic costs associated with nonindigenous species in the United States.
Withgott, J. (2002). California tries to rub out the monster of the lagoon. Science, 295,
2201-2202.
Global Invasive Species Database
http://issg.appfa.auckland.ac.nz/database/welcome/
Literature review on the aquarium strain of Caulerpa taxifolia
Madl, P., Yip, M. (2003).
http://www.sbg.ac.at/ipk/avstudio/pierofun/ct/caulerpa.htm
http://www.unep.ch/seas/main/legal/lcbd.html
http://earthwatch.unep.net/biodiversity/invasivespecies.php
http://www.anstaskforce.gov/nanpca.htm
http://www.csc.noaa.gov/cmfp/reference/National_Invasive_Species_Act_1996.htm
http://www.nepa.noaa.gov/eo13112.pdf
http://ccpr.freedom.org/invasive/eo13112.html
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