What Even Is An Invasive Species, Anyway?

I’m sure we’ve all heard the term “invasive species” thrown around in conversation, but what exactly does that mean? Are invasive species anything that causes harm to an ecosystem? Or something that is not native to the area it is found? Well, actually, it is a combination of both. An invasive species is any organism (plant, animal, insect, fungus, etc.) that is not native to an area and is causing harm to the environment (including animals), humans, or even the economy. Majority of these species are transported to new habitats due to human activities (intentional or not), such as on cargo ships (in ballast water, in the shipped goods, etc.), car tires, the pet trade, and much more.

Many species that end up a new habitat have trouble colonizing, either because of a new environmental factor (weather, etc.), an already occupied niche (an already present species is better adapted and outcompeting the invader), or they cannot find any other individuals with which to mate. However, if they are able to establish in this new place, many invasive species cause a lot of harm due to their ability to quickly reproduce once they get started. On top of this, many species do not have predators in their non-native habitats, so they can be even more prolific than they would be in their natural home.

So, why is this so bad? Isn’t species diversity a good thing? This is the ever-present argument surrounding invasive species. However, many ecologists believe that while it is good to have habitats rich in different species, it is the most beneficial for the environment if those species are native, meaning they have evolved to live there. The problem with invasive species is that, not only are they establishing and reproducing in a place they “don’t belong”, but they are taking resources from species that spent thousands (if not millions) of years evolving to fit into this particular habitat. By doing this, they are making it more difficult for the native species to thrive, leading to population declines, and even extinctions. Along with outcompeting natives, invasive species can also carry new diseases that local species are not protected against, again leading to huge decreases in population sizes. Finally, invasive species tend to be generalist feeders, meaning they do not require one (or a few) specific organism as their source of food, but rather can eat a wide range of things. This means that organisms that have evolved to defend off only their natural predators now have no protection against this new species and struggle to keep their population on its feet.

There are many other ways invasive species may cause harm to the environment, people, and the economy that were not touched on in this post. So, check back on our blog in the near future and we will be covering specific examples of invasive species in Maryland that you may have heard of! Shown here with this blog are two examples of invasive species in Maryland, the zebra mussel (USFWS photo - public domain) and the starling (a Creative Commons photo).

Author: Sammy Baker

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