A large worm squirms around close to the surface of the uneven layer of soil while tall, bright green spires of grass reach high, obscuring the surfacing invertebrate from view. Many people can recall seeing something like this. Most would also say that these slimy organisms are key decomposers to an ecosystem, offering vital nutrients to the soil that help support the autotrophs that live within it, but not all is as it appears. As a matter of fact, foreign earthworms may be as harmful to an ecosystem as its relative, the tapeworm, is harmful to our body.
Before we take a look about how foreign earthworms can be detrimental to a forest, it should be stated how they got to northern states like Michigan. Many years ago, glaciers roamed about the environment, and killed all of the native worms that lived in the Great Lakes area. Because of this, our forest has changed over the course of thousands of years to accept these changes and live without the help of earthworms. European colonizers then came and dumped soil and rocks they used as a ballast, as well as the importing of foreign plants, all of which could have carried exotic earthworms and introduced them to the environment. This, as one can imagine, caused problems.
Worms can usually be found in the floors of hardwood forests. This ecosystem can be home to hundreds of thousands of plant species, and earthworms can have a devastating effect on almost all autotrophs in the area. They can damage a plant’s roots, eat/kill fungi (a beneficial decomposer), change in dominant bacteria in an area, and rapid consumption of duff layer causing lack of forest redevelopment. Someone might think to themselves that this is just one part of an ecosystem, and therefore it’s not that big of a deal, but this is not true. All ecosystems hold an underlying fact: all life is connected and you cannot change one thing without changing the entire ecosystem. This means that the harmful effects earthworms have on plants could affect other organisms in the ecosystem.
On top of all this, worms also change the amount of nutrient availability in an ecosystem. According to The Great Lakes Worm Watch, “After earthworms invade a hardwood forests, the rate of decomposition and nutrient release is faster than the rate of uptake by plants and some of these nutrients are lost through the process of leaching… Two things increase the likelihood of nutrient leaching. First, there are not enough plants or root systems to absorb the amount of nutrients available. Second, with all of those earthworm burrows, water can wash the dissolved nutrients down through the soil, below the plant roots or out into adjacent wetlands, rivers and streams.”
Prior to learning all this, I had the same idea of worms as probably most people did, that worms are beneficial to an ecosystem. Being aware of this makes me more aware of the environment around me and how it can be affected.
“Forest Ecology and Worms ».” Great Lakes Worm Watch. Web. 23 June 2016.