The Moncton and Riverview Riverfront trails wind along opposing sides of the Petitcodiac River offering visitors beautiful views of the water and wetlands. Large parts of these trails are surrounded by native grasses like cattails which thrive by the muddy water. However, scattered throughout these banks are impenetrable fortresses of stocky grass. Rising high above all other surrounding plants, these patches vary in size ranging from small, sparse stocks to what looks like a vast forest (as shown in figure 1 some of these infestations are large enough to be distinguishable in satellite – imagery). Infestations of invasive phragmites (Phragmites australis subsp. australis) are becoming an increasingly familiar sight across New Brunswick’s wetlands. Thankfully, the PWA and others are beginning to address the issue.
In 2005, Agriculture and Agrifood Canada identified invasive phragmites as the nation’s worst invasive plant. While there is also a native species of phragmites (Phragmites australis subsp. americanus), it is outcompeted by its invasive counterpart. The species spreads incredibly easily using several different strategies. Seeds are dispersed through the air and water and can be easily moved by animals including humans. Phragmites take advantage of its extensive underground root and rhizome structures; as roots spread, they create distant “satellite” infestations. By the time a single parent plant is 3 years old, it could have already produced up to 6 new plants!
The aggressive invader outcompetes native species for necessary resources like light, water, nutrients, and space. By emerging early in the season and forming dense, impenetrable stands (the plant can grow up to 5 meters tall with up to 200 stems per square meter) invasive phragmites prevents other species from growing. While you would think this would be enough, it has an even more devilish tactic up its sleeve; the plant releases toxins from its rapidly growing root systems into the soil hindering and/ or killing surrounding plants. The presence of invasive phragmites in any given area will decrease biodiversity and negatively affect native wildlife including species at risk like the wood turtle.
In Ontario, where the plant has extensively taken root, the species has been associated with several significant environmental, economic, and social consequences. Because it grows so quickly, invasive phragmites can impact water levels and dry out wetlands. At the end of the season, the die-off leaves a thick layer of biomass that decomposes slowly and collects over the course of many seasons. This is especially significant in a warming world because these dead stalks are highly combustible increasing the risk of fires. While New Brunswick’s infestations are not quite as extensive as Ontario’s, immediate action is needed if this is to remain true.
Phragmites is incredibly difficult to get rid of, sometimes nearly impossible without the use of heavy herbicides. For this reason, prevention is far more effective and economical than trying to remove it once it has been fully established—moreover, small, young stands are also easier to get rid of.
The PWA, Nature Conservancy Canada, New Brunswick Invasive Species Council, Sentinelles Petitcodiac Riverkeeper, and the Fundy Biosphere Region are working together to map and control phragmites around the region. In July of this summer, these groups completed their first removal event in order to test the efficacy of different removal methods (click here to see us on CBC!). Although the plant is found throughout the province, Moncton and Riverview are considered ‘hotspots’. As a result, this season’s efforts have focused on a small section of the infestations lining the Petitcodiac River. One large area was cut and tarped, another was just cut, and another was spaded (a process that involves manually removing the stocks and their roots with spade shovels.) These groups will continue monitoring this removal site to see which methods were the most effective to improve future efforts.
If you want to help control and prevent the spread of invasive phragmites, you can locate and identify infestations on the inaturalist app. This site can help you correctly identify the species and distinguish it from its native counterpart.
To be entered to win our #25watershedmoments giveaway, post a picture from the Moncton or the Riverview trails. If you are interested in seeing our removal site, you can head to these coordinates 46.080692, -64.767413
Other press coverage:
Invasive plant species thriving in New Brunswick | CTV News
The problem with phragmites: Dealing with an invasive species | CBC.ca
https://www.cbc.ca/listen/live-radio/1-83/clip/16000056
Fighting phragmites: One of Canada’s worst invasive species now in N.B. | CBC News
L’une des pires espèces envahissantes gagne du terrain au Nouveau-Brunswick | Radio-Canada.ca
https://www.acadienouvelle.com/actualites/2023/07/28/mobilisation-pour-la-lutte-au-roseau-commun/
Lutter contre le roseau commun pour préserver nos milieux humides – Le Moniteur Acadien