Climate Change and Invasive Species:Threats to Great Lakes Ecosystems

Andrew T. KozichMichigan 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.

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.

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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.

ConclusionsThe 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.

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.

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.

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 out-competing native fish species.

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.

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.