A Primer on Invasive Alien Species and an introduction to Phragmites australis

Date: February 28, 2019 Author: EcoSpark Categories: Latest

A Primer on Invasive Alien Species and an introduction to Phragmites australis

Phragmites australis, also known as Phragmites or Common reed is a prolific invader of wetlands, and has been deemed one of the worst invaders by Agriculture and Agri-food Canada1. Keep reading to learn more about Phragmites and how EcoSpark can help you fight invasive species.  

Just what is an invasive species anyway? According to the Government of Canada’s 2004 “An Invasive Alien Species Strategy for Canada” document, an alien species is an organism that has entered into a new region due to human intervention. What makes a species invasive is its potential to cause social (including human health), economic, and/or ecological harm2. In other words, all invasive species are aliens, but not all aliens are invasive!

The human intervention component of the definition is important. It could have been an accident – the Zebra mussel, for example, which came from the Black Sea region of Eurasia via ballast water4. Or it could have been intentional, for example, through the garden plant trade. Phragmites also came from Eurasia, but it is not clear how it got here3.  

Organisms that expanded out of their historical area and into a new one without human intervention are not considered to be aliens, and therefore, can’t be considered invasive either. The Virginia opossum is a good example. Because it meandered its way up to Canada on its own, it is considered a native species and enjoys protection under Schedule 1 of the Ministry of Natural Resources’ Fish and Wildlife Conservation Act.

To understand why invasive species are a problem, you have to think on an evolutionary scale. Organisms do not evolve in a vacuum - they interact with other organisms and their environment. Imagine a situation where a plant has spent millennia evolving anti-herbivore defenses, while herbivores were evolving ways of counteracting them. If that same plant was moved to a climatically suitable environment with all its anti-herbivore defenses intact and nothing that can successfully eat the plant – well you can imagine what might happen. Phragmites has been altering plant communities in Canada for decades by outcompeting native plants through incredibly fast growth rates, root chemicals that impede other plants, and adaptations that allow it to access resources like oxygen and water better than other plants5. There is nothing here in Canada that eats Phragmites, but introducing something that does would have to be a very carefully thought out, or else THAT organism could become invasive too.

As Phragmites takes over and forms dense stands, the transpiration (water vapour leaving the plant) rate for the area increases, which means wet areas dry out. The stalks from previous years take a very long time to decompose, and layer upon layer of plant material and other debris increases the area’s elevation3. That combined with lower water levels changes the ecosystem, which translates to a change or a reduction in the types of ecosystem services that humans rely on: erosion and flooding control, filtration of contaminants and excess nutrients, and nature-based recreation. There is also evidence that these dense stands can impact crop yields, and lower property values as views from homes are blocked1.

EcoSpark can facilitate your Phragmites fighting endeavours through a couple programs, including School Watch! Through this program, teachers can register for training workshops where trained EcoSpark staff will provide you with the information and resources needed to lead citizen science projects right on school property. We can even come out to co-facilitate a student session! Registration for School Watch is open until April 5th, and includes a colour copy of the School Watch Guide. Another program is Park Watch, which aims at providing volunteer park/community groups with the information, resources, and support they need to start their own citizen science projects. One of the citizen science projects you’ll find in both the School Watch and Park Watch guides is EDDMapS. This is a wonderful invasive species mapping tool where you submit a photo of the organism you saw, an expert confirms the sighting, and a point is added to a map. Doing this contributes to a huge data set that researchers and land managers can use to help inform invasive species management programs.


Last year, with help from the City of Toronto’s Community Stewardship Program, and Humber College, EcoSpark was able to carry out preliminary research into a promising new Phragmites management protocol called spading. This technique is showing promising results, including lower density of plants in a stand, smaller stalk diameters, and an increase in plant biodiversity. We are excited to continue the program this year and into the future not only to help eradicate the plant across several sites in Toronto, but to hopefully inform management techniques to be used wherever the plant is found.


[1] https://www.ontario.ca/page/phragmites

[2] http://publications.gc.ca/collections/collection_2014/ec/CW66-394-2004-eng.pdf

[3] http://www.invadingspecies.com/invasive-phragmites/

[4] http://www.invadingspecies.com/zebra-quagga-mussels/

[5] https://dr6j45jk9xcmk.cloudfront.net/documents/3226/phragmites-fact-sheet.pdf  

Sara's passion for ecology, bird watching, and educating the public about the environment started during her undergraduate degree, where she focused on biodiversity, conservation, and ecology. Through a graduate degree in Environmental Science, Sara discovered the immense value of citizen science for advancing conservation, and has been working professionally and on a volunteer basis to encourage the public to take an active role in protecting their local environment and beyond. Working with EcoSpark was the logical way forward as Sara continues with her passion of spreading knowledge about nature and how fun and amazing it can be!