Invasive Species: A real threat!


This weekend I spent a morning with my conservation biology students, and Dr. Bill Bromer of St. Francis University and his students, sampling a stream for crayfish. You may think it strange to wade through a stream and collect arthropods with pincers that they are not afraid to use. Some of the students experienced the pinching firsthand. However, these small sacrifices were made in the name of science.

Monitoring invasive species was the true purpose of our morning adventure. The rusty crayfish is native to North America but not to northeastern Illinois, Wisconsin, and Minnesota fresh waters. People used them as fish bait, introducing this organism into new habitats. Unused bait was then dumped into the water, giving them an opportunity to spread. The rusty crayfish has no predator in these waters so they spread unchecked and outcompeted native crayfish for resources such as living space and food. The decline of native populations can have a serious impact on the food web. There are organisms that depend on native populations for food, and the crayfish keep other species in check too. Over time, the health of these aquatic ecosystems can be jeopardized.

Although writing about the adventures of my conservation biology class is worthwhile, the true purpose of my blog post is to discuss invasive species. I have invested some time studying the genus Dresseina, which includes the zebra and quagga mussels, so I am very interested in this environmental issue. These aquatic organisms changed the Great Lakes after their accidental introduction. In less than twenty years, the zebra mussel spread to all the major fresh waters east of the Mississippi. Their voracious filter feeding habits reduce the food supply for native species. They also attach in very large numbers to surfaces, as high as 750,000 per square meter, which damages infrastructure. Currently, the only thing we can do is control the populations of these invasive mussels and work to prevent their spread. Their complete eradication does not seem likely.

Invasive, introduced, exotic, non-native, and nuisance are some adjectives used to describe this group of organisms. Sometimes the organisms are introduced accidentally. People who purchased firewood from other states introduced the emerald ash borer to Illinois. The wood that was used to manufacture pallets in China carried the Asian long-horned beetle to the United States. People discharged ballast water into the Great Lakes, releasing invaders. Other times people intentionally bring exotic species to new habitats because they find them attractive. Later, problems arise. Buckthorn was introduced as a natural fence, only to spread and out-compete native trees and grasses, creating useless forests of thickets that provide no value to wildlife or humans.

As a global economy, opportunities are created every day for the spread of organisms accidentally or intentionally, e.g., the exotic pet trade. Think about your food and drink of choice. Potatoes, corn, wheat, rice, coffee, and soybeans are very common items in people’s diets that are grown around the world. They were discovered and brought to people’s homelands because of their economic value. For example, coffee is native to Africa, but most people think South America when they see a coffee bean. The demand for coffee is so big that rain forests are cut down so you can have your morning brew. Does this seem right to you?

Wherever invasive species spread, they change the ecosystem dynamics and create problems. Many times, we do not care. However, when it hurts our pocketbooks, it becomes a pressing issue, e.g., fish populations declining or municipal infrastructure and personal property damaged. In addition, if the organisms threaten our safety, it makes the daily news – monitor lizards in Florida, alligators in Illinois (yes, you read that correctly).

We definitely know better! We need to be more vigilant when it comes to invasive species. I encourage you to learn more about invasive species. I recommend visiting

About Dr. Jerry Kavouras

Dr. Jerry Kavouras is Associate Professor and Chair of Biology at Lewis University. He can be found on LinkedIn as well.

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