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- Aquatic Invasives
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Why Should We Care?
Economics
In the United States, expenses associated with ecological damage and control of invasive species is estimated at $137 billion per year and increasing.1
In Wisconsin, some industries affected negatively by invasive species include sport and commercial fishing, forestry, and raw water users (power companies and utilities). These expenses are passed on to Wisconsin consumers (for example, in the form of higher water and electric bills)
The Great Lakes sport and commercial fishing industry, valued at almost $4.5 billion, is at risk due to the growing numbers of invasive species present in its waters. For example, invasive round gobies eat the eggs of sport fish such as small-mouth bass, trout and sturgeon in the nearshore areas of Lake Michigan.
Invasive shrubs such as buckthorn and honeysuckle prevent the regeneration of young trees, causing a long term but very serious impact on forestry in Wisconsin - a $20 billion dollar per year industry. Control of buckthorn alone has been estimated at $500-$2,000 per acre over multiple years.
In 2001, Wisconsin Electric Power Company reported that they were spending $1.2 million per year in the control of zebra mussels on their Lake Michigan power plants. These animals congregate on and clog intake and distribution pipes.
Health
Some invasive species may cause significant health problems. For example, a South American strain of human cholera-causing bacteria was found in ballast water tanks of ships in the port of Mobile, Alabama in 1991. Also, sharp zebra mussel shells can cut the feet of unsuspecting swimmers and waders.
Health risks aren't only confined to water-dwelling invasive species. Simply rubbing against wild parsnip with bare skin can cause burned and blistering arms and legs. This roadside and grassland invasive is spreading rapidly in Wisconsin, but few people know of its dangerous impacts.
Ecology
Humans have created conditions where plants and animals can aggressively invade and dominate natural areas and waterways in three ways:
- Introducing exotic species (from other regions or countries) who lack natural competitors and predators to keep them in check.
- Disrupting the delicate balance of native ecosystems by changing environmental conditions (e.g., stream sedimentation, ditching, building roads) or by restricting or eliminating natural processes (e.g., fire). In such instances, even some native plants and animals can become invasive.
- Spreading invasive species through various methods (e.g., moving watercrafts from waterbody to waterbody without removing invasive plants and animals, roadside mowing, and importing firewood).
The net result is a loss of diversity of our native plants and animals as invasive species rapidly multiply and take over. About 42% of the species on the federal Threatened or Endangered species lists are at risk primarily because of invasive species.
In our waterways, the rapid spread of zebra mussels shows how profoundly an invasive species can alter the environment. These tiny mussels - with huge appetites for microscopic plants and animals - rapidly reproduce and through their large numbers are capable of severely altering their environment by reducing the food supply for native organisms and by enhancing conditions for the rapid growth of blue-green algae and aquatic vegetation.
In our woodlands, garlic mustard can completely cover the ground with first- and second-year plants in a matter of years. This European garden herb not only steals most light and nutrient resources from our native wildflowers, it is also thought to secrete a chemical into the soil that inhibits growth of other plants.
Recreation
Hunters, hikers and birdwatchers are finding that they can no longer walk in their favorite natural areas. Thorny multiflora rose, dense stands of buckthorn and other invaders fill in the understory of our once open forests and grasslands. As the habitat is modified by such invasive plant species, the wildlife that depends on it disappears as well. Invasive animals such as the mute swan can also change our wildlife opportunities by chasing away all waterfowl from the waterbodies that they occupy.
Fishing outings can result in disappointment as aquatic invasive species modify our lake and stream habitat. Invasive animals such as the rusty crayfish gobble up aquatic plants like underwater lawn mowers, reducing habitat for native fish at every stage of their life cycle. They may even eat the eggs of our favorite sport fish. Eurasian water milfoil can clog boat motors, preventing free movement throughout Wisconsin waters.
This threatens a national sport and commercial fishing industry that supports 81,000 jobs in the Great Lakes region.
References
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