In the article I came across, it discusses an “alien invasion” of sorts; however, this isn’t just any alien. In fact, this alien can be under your feet right now: non-native earthworms. Earthworms (not the alien kind) are described as “[m]ostly invisible and largely unappreciated” – these friendly creatures are invaluable to not only farmers and gardeners but you! In fact, these creatures support a lot of the agriculture you have grown to love and enjoy. “What makes them so helpful?” I’m sure you’re asking. Well, mainly, earthworm movement leaves an unimaginable amount of tunnels that allow air, water, and important nutrients to penetrate deep into the soil. On top of that, their waste doubles as a rich fertilizer!


Earthworms are far from always being sunshine and rainbows, though. When the wrong type of earthworm reaches the wrong type of ecosystem, chaos can easily ensue. This is what’s happening now all across North America with alien earthworms. Research has shown that, specifically in the northern broadleaf forests of the U.S. and Canada, alien earthworms have caused severe stress on local trees such as sugar maples – Acer saccharum – by altering the microhabitat of their soils. Even more, it is affecting local farmers as well. This microscopic impact can cause a snowball effect, allowing invasive species of plants to spread in an expedited manner. Isn’t it interesting and ironic that an organism known for actually improving soil can lead to poorer-quality crops and lower yield rates?

The article also spoke about specific research – drawing on extensive records spanning from 1891 to 2021, researchers compiled a database encompassing native and alien earthworm species. This dataset was augmented by another documenting interceptions of alien earthworms at U.S. borders from 1945 to 1975. Combined with new machine learning techniques, the team reconstructed the probable pathways of origin and spread of alien earthworm species. Their analysis revealed the presence of alien earthworms in a staggering 97% of soils studied across North America, with a higher (and extremely concerning) presence observed in the northern regions compared to the southern and western areas. 

Alien earthworms constituted 23% of the continent’s total of 308 earthworm species and comprised 12 of the 13 most widely distributed species. The article gave a fascinating contrast as well: only 8% of fish species, 6% of mammal species, and 2% of insects and arachnids in the U.S. are of alien origin. Lead author of the study, Jérôme Mathieu, an associate professor of ecology at the Sorbonne, emphasized that these proportions are likely to increase even more due to human activities, posing a significant threat to native earthworm populations, and to the future of our agricultural sector.

In terms of linking this back to our AP Bio course, it is easy to mention how we just learned about food webs, food chains, and trophic levels. We learned how delicate these intricate ecosystems are, and learned that when invasive and non-native species are introduced into an ecosystem, it (the ecosystem) becomes prone to collapse. Further, we can continue to apply this to the genetics unit that we are learning right now; as earthworms change the fundamental pH and nutrients in the soil, new adaptations will likely need to arise to, well, adapt to new conditions.

Who knew that such a small creature could have such a huge (and dangerous) impact on the ecosystems around us? Let me know what you think about it.


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