What are Invasive Species?

International Maritime Organization. (2020). International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BMW). Author. http://www.imo.org/en/About/Conventions/ListOfConventions/Pages/International-Convention-for-the-Control-and-Management-of-Ships’-Ballast-Water-and-Sediments-(BWM).aspx

Ricciardi, A. (2012). Invasive Species. Pp. 5547–5560 In: Encyclopedia of Sustainability Science and Technology (R.A.Meyers, ed.), Springer.

Sophie Koch. (2017). Invasive Zebra Mussels. U.S. National Park Service.

What are Invasive Species? During these times of recent difficulty, it may seem far-fetched to reflect on life beyond the immediacies of the pandemic and our own homes. It’s been a little over a month since our daily lives began to undergo necessary change, and while I was able to stay positive at the beginning, lack of motivation has been increasingly seeping into my life. However, the rapid approach of Earth Day serves as a great reminder that we cannot forget about our planet and the daily challenges it, human, and animal lives face. These problems are continuous; they don’t stop because we’ve been forced to put our lives on pause. Today’s blog topic focuses on one of these problems, an issue less commonly known to be an environmental threat: invasive species in marine environments.

While it is well known that things such as plastic and fossil fuel pollution are harmful to the environment, some may be surprised to learn that animals or plants themselves can pose a direct threat to an ecosystem. Broadly, invasive species are plants and animals that evolved in one area and have been moved to a new location that they have not historically occupied. However, this definition does not cover the whole story and we must be careful when classifying species as invasive. For a species to be considered invasive, it must meet multiple criteria. For one, its new region must be outside of its native range (the place in which it evolved and has evolutionary history). Additionally, it must establish a population that not only is able to sustain itself for generations, but one that spreads greatly and/or significantly affects the environment. These specifications are important for a few reasons. For one, most species introduced to an area outside of their historical range do not continue to survive on a generational basis. Moreover, even if a species does manage to survive in the new territory, there is no guarantee that it spreads much, nor that it has any large impact on its new environment. In light of this, very few species introduced into a new area are actually considered invasive species.

You might ask how invasive species are transported to new regions. Typically, they are moved through human action, purposefully or not. In the case of intentional transport, marine invasive species are sometimes directly added to new ecosystems, either for recreational purposes like fishing, or in the hope of “fixing” an ecological problem. On the other hand, species are commonly transported via the ballast water of commercial or other large ships. In this process, the ship will take in ballast water in one location and dump it out in another. Oftentimes, that water contains some organisms and as a result, when the water is dumped elsewhere, those now non-native organisms are too.

While I will not go into detail here about specific species, I feel compelled to list some examples of marine invasives. Some particularly notorious cases include Sea Walnuts (Ctenophores), which were moved from the east coast waters of the North and South America to the Black Sea; green crabs, from coastal Europe to multiple continents, especially North America; and lionfish, which were introduced into the Gulf of Mexico. Additionally, it should be mentioned that not all species transported as a result of marine industry practices are necessarily marine species. One example of this is the zebra mussel, originally from the Black and Caspian Seas, which was found in the freshwater systems of the Great Lakes area of North America and likely transported through ballast water.

In general, invasive species can have multiple and severe negative environmental and socioeconomic impacts. Among these environmental impacts are loss of biodiversity and increases in harmful environmental events such as toxic algal blooms. In fact, the resulting biodiversity loss is largely what enables events like this. There are economic consequences too. Because invasive species can be so significantly harmful to native species populations, they can wipe out whole fisheries. This has been detrimental to countries that heavily rely on their fisheries for economic security.

This is not to say that we are helpless in preventing the spread and resulting consequences of invasives. Encouraging action taken by the maritime industry is the International Maritime Organization’s (IMO) Ballast Water Convention, adopted in 2004. Designed to mitigate the impacts of invasive species through the transport of ballast water, the Convention requires ships to filter ballast discharge through a ballast water treatment system. This significant step in invasive species mitigation policy is still in place today and, in the United States, is rigorously enforced by the United States Coast Guard.

The challenges posed to humans and the Earth by invasive species are numerous, great, and increasing with globalization. Though talk of plastic and fossil fuel pollution remain the most prevalent topics in environmental discourse today, invasive species must be addressed and not forgotten. Our Earth is under ever increasing pressure. We can help it by learning and then acting with our newfound knowledge. Ultimately, Earth Day exists to remind us of that. It’s a day where we can celebrate the progress we’ve made thus far and promote ideas for future environmental progress.

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