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Climate Change and Invasive Species:
Threats to Great Lakes Ecosystems
Andrew T. Kozich
Michigan Technological University
School of Forest Resources and Environmental Science
What are Invasive Species?
Invasive species are non-native organisms capable of adversely
affecting ecosystems they colonize. They can include all types of
organisms, but aquatic and terrestrial plants and animals tend to be the
most familiar. Most invasive species possess traits that provide
competitive advantages over native species, including high dispersal
ability, rapid reproduction, fast growth, and tolerance of a wide range of
environmental conditions.
Substantial ecosystem disruptions can result as invasive species
replace native ones. Invasive species can carry diseases for which native
species have no defense. They can greatly disrupt food webs. Invasive
herbivores can cause geomorphic damage by denuding sensitive
landscapes such as stream banks, which in turn may alter adjoining
aquatic communities. In all, the most common consequence of invasive
species tends to be reduced biodiversity. Human economic interests are
often impaired by invasive species, including fishing, forestry, and
agricultural industries.
Aquatic Invasive Species of the Great Lakes Region
Asian carp includes many related species of
warm-water fish that severely threaten the
Great Lakes. They could potentially displace
native cold-water fish species if climate change
raises lake temperatures as speculated. Asian
carp are voracious eaters that would certainly
disrupt aquatic food webs.
Rainbow smelt (Osmerus mordax) are a very
small invasive fish that has disrupted fishing
industries in many parts of the Great Lakes
region by rapid reproduction and outcompeting native fish species.
Round goby (Neogobius melanostomus) is a
small, bottom-dwelling fish native to central
Eurasia. It arrived in the Great Lakes in ballast
water, and can tolerate warm, degraded
conditions. It has already had profound effects
on the ecology of the Great Lakes.
What Can be Done?
Once established, invasive species can be tremendously difficult to
contain or eradicate. In some cases researchers have developed
chemicals to poison invasive species, but these often have undesirable
side-effects. Physical removal of invaders is sometimes an effective
measure, but can be very labor-intensive and time-consuming. Predator
species may be imported that effectively limit expansion of the invasive
species, but this strategy can be dangerous if there are uncertainties
regarding the range of effects of the predator species. Management
approaches often involve a combination of these various strategies.
The best strategy is to prevent the establishment of invasive species
by limiting their means of potential dispersal. Once invaders are
detected, early treatment typically results in the greatest likelihood for
successful removal. Sometimes establishment can not be reversed but
subsequent dispersal to additional areas may be contained. Treatment of
smaller, isolated establishments is usually more feasible than larger,
wide-spread ones. Management options can be very expensive, so a
cost-benefit approach may best suggest where to focus efforts. Public
education is very important, as residents should be aware of the
consequences of planting or transporting invasive species.
The Great Lakes Region and Climate Change
Great Lakes ecosystems are threatened by a wide range of invasive
species. Aquatic invaders typically include fish, mussels, plants, and
crustaceans. The emerald ash borer (Agrilus planipennis) is an example
of an upland insect devastating regional forests.
Dispersal of invasive species is often assisted by humans, as
invaders may “hitch a ride” in firewood, clothing, or ballast water of ships.
Many invasive plants are intentionally planted. Invasive fish and upland
animals may disperse after the removal of natural physical barriers that
traditionally limited their range. Invasive species also tend to be effective
colonizers of disturbed landscapes that result from human activities.
Ecological effects of climate change are likely to accelerate the
spread of invasive species. Changes in temperature and precipitation
could alter the ranges of native upland species, presenting opportunities
for invasive species to establish. Native aquatic species may be unable
to tolerate changes in water depth, duration, chemistry, and temperature.
Fresh-water ecosystems are particularly vulnerable to threats because of
their high degrees of isolation and endemism. Conditions confronted by
native species of all types could result in physiological stresses, the
inability to compete with invaders, and their ultimate extirpation from
many areas.
Ironically, human attempts to mitigate climate change could also
create conditions favorable for invasive species. Lands converted to
energy crop production for biofuels would essentially be monocultures
that are prime targets for invasive insects. Wetland restoration efforts
may be increased to store atmospheric carbon, but research shows that
these sites are prone to problems with invasive plants.
Conclusions
The sea lamprey (Petromyzon marinus) is a
long, narrow invasive fish that attaches itself to
larger fish with a suction-cup like mouth. Victims
typically die from blood loss to the lamprey.
The crustacean spiny water flea
(Bythotrephes cederstroemi) also
arrived by ballast water. It
consumes large amounts of
zooplankton, disrupting Great
Lakes food webs.
The zebra mussel (Dreissena polymorpha) is an invasive
mussel that arrived by ballast water. It has already caused
great economic distress to humans, particularly disrupting
boats, harbors, and structures. The increased water
clarity that results from their voracious filter-feeding could
exacerbate concerns for water changes associated with
climate change.
The Great Lakes region is susceptible to threats from a wide range
of invasive species, and many threats result from the effects of climate
change. Aquatic invaders are perhaps the most troubling, as their
establishment could have potentially devastating ecological and
economic consequences in the region. Researchers and natural
resource managers need to continue their efforts to prevent, control, and
eradicate invasive species while searching for promising new solutions.
References
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Eurasian watermilfoil (Myriophyllum spicatum) is
an invasive submerged plant. It thrives in shallow,
warm, nutrient-rich waters, a scenario likely to
worsen with the potential effects of climate change.
The Common reed (Phragmites australis) is
an invasive wetland plant with devastating
effects to the areas it invades. It is a prolific
reproducer and is taller than native species.
It is likely to continue its northward migration
as climate change occurs in the region.
Purple loosestrife (Lythrum salicaria) is an
invasive wetland plant problematic to the
Great Lakes region. Like the common reed,
its establishment tends to result in
monocultures with little biodiversity.
Rahel, F., and J. Olden. 2008. Assessing the Effects of Climate Change on Aquatic Invasive Species. Conservation Biology
22(3):521-533.
Ricciardi, A. 2007. Are Modern Biological Invasions an Unprecedented Form of Global Change? Conservation Biology
21(2):329-336.
Vander Zanden, M., and J. Olden. 2008. A Management Framework for Preventing the Secondary Spread of Aquatic Invasive
Species. Canadian Journal of Fisheries and Aquatic Science 65:1512-1522.