What Are Invasive Species?

Submitted by jwalton on May 6, 2019

Climate Victory Gardeners may come across invasive species in the garden, and it’s important to know what to do in this case. How much harm do they cause? How do we get rid of them? And what can we do to prevent their spread in the first place? Fortunately, Green America volunteer Jesse Cross has the answers.

My name's Jesse. I'm a volunteer at Green America and an environmental science and economics double major at American University. When I was in high school, I spent a summer volunteering for an environmental organization called Duke Farms. This 2,742 acre property in Hillsborough, New Jersey promotes native biodiversity through preserving natural ecosystems, practicing sustainable farming techniques, and educating visitors on the importance of sustainability and conservation.

A large portion of that volunteer work was centered around one task: invasive species management, or as its more commonly known: weeding.

I spent long hours in the summer sun, ripping plants out of the ground and off of trees. My arms were covered in itchy poison ivy. And, while I mostly enjoyed the work, it also left me wondering how I had come to the conclusion that weeding was a productive use of my time. Was I was even weeding out the right plant?

I was there to manage invasive species. What counts as an invasive species? 

An invasive species is not native to a specific region or ecosystem. It usually has no predators in this environment, which allows it to outcompete and displace native species and cause harmful ecosystem imbalance. Invasives may transmit diseases that native plants are not resistant to, or even consume or prey upon native species. All these actions can greatly decrease the biodiversity of an area.

Some examples of invasive species include the small carp grass, a grass from Eastern Asia that has spread across nearly half of the United States. The Australian cane toad is a poisonous amphibian from South America that kills anything that tries to eat it and is spreading rapidly across the Australian continent, wreaking havoc on Australia's natural wildlife. The Zebra Mussel is a shellfish from the Caspian and Black seas of Eastern Europe that has spread across the US and outcompetes native shellfish for space in aquatic environments. Each of these species had evolved to fill an ecological niche in their home environments, and only became invasive when moved to a new location where their traits allow them to spread and overcome local species.

Humans play a role in the spread of these invasive species through global trade and travel. Knowingly or unknowingly, people move plants and animals across the world to new environments. In many cases, these species are not able to survive, but in the case of invasives, they thrive. A combination of hospitable environment and reduced predation enables them to spread across an ecosystem, taking space and resources away from native species that, unlike invasive species, are burdened by environmental pressures and predators.

While many invasives can drive native species to extinction, there are some exceptions to this trend. Organisms have been naturally migrating around the world for millions of years.  And, today, there are many non-native species, which are also non-invasive, meaning they do not invade the surrounding environment and outcompete native species. So, there can be some coexistence.

Ultimately, it's important to care about invasive species, because it's important to care for our local natural ecosystems. And, humans have a stake in this. Invasive species can decimate local plant and wildlife populations, which in turn causes great damage to local habitats that we rely on for recreation, business, and food.

Getting rid of an established invasive species can be very difficult. As I learned at Duke Farms, weeding out an invasive species is a laborious and time-consuming process that must be repeated over and over again to keep these species at bay. As shown by the small carp grass, the Australian cane toad, and the zebra mussel, invasive species spread and reproduce so quickly that it's impossible to keep up with these species to entirely remove them. Because of this, the best way to stop invasive species from wrecking a native ecosystem is stop them from even getting there in the first place. Laws have been enacted that regulate when and where ships can empty their ballast water, a popular travel method of aquatic species. Similarly, international commerce is inspected to reduce transport of invasive species.

You can help at the individual level too, especially when traveling, working with animals, or spending time outdoors. Always clean your fishing and hiking gear to help prevent taking invasive hitchhikers with you. Don’t bring unknown plants or animals home with you. If you have an exotic pet you don't wish to care for anymore, take it to a shelter instead of releasing it out your backdoor. If you have a plant to discard that you’re unsure of, be sure to destroy it and throw it away instead of tossing into a compost pile where it could spread.

You can help in your community by volunteering at local volunteer removal events that help prevent the spread of invasive species. It’s hard work but also rewarding when you see how much of a difference clearing out an invasive species from a habitat can make. Or volunteer at a local farm like Duke Farms.

You can even take part in your own back yard. Plant native species to help preserve your area's local biodiversity. The best defense against invasive species is to plant a diverse, healthy ecosystem on your property, full of native species that do not allow much room or opportunity to for invasive species to spread. You can plant a Climate Victory Garden, full of perennial plants and a healthy soils that feed you and increase the resiliency of the habitats around you. Your local garden center or agricultural extension agent can help you determine which plants are appropriate for your area.

Join other farmers and gardeners in this movement. Happy weeding!

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