You’ve probably heard this from us before: if you see an invasive species, report it to the web-based mapping system EDDMapS. Reports allow for early detection and response, which can lead to the successful management of an invasive species. But can one person submitting a photo from their phone actually make a difference in preventing the spread of invasives?
In 2020, a local recreational paddler was kayaking through the Welland River, a mostly deep and slow-moving waterway that starts just south of the Southern Ontario City of Hamilton. This popular paddling destination eventually flows into the Niagara River, passing through the Golden Horseshoe cities of Welland and Niagara Falls on the way.
Out on the river, one might expect to see native species such as water celery and coontails. But on this summer day, the paddler came across shimmering, light green rosettes floating on the surface, each one measuring up to 30 cm in diameter. As harmless as these plants may have looked, the paddler suspected something was amiss and reported their sighting to EDDMapS.
Two initial photos of EWC rosettes in the Welland River reported to EDDMapS in 2020
The experts at EDDMapS determined that the paddler did in fact report an invasive species: European Water Chestnut (EWC). This sighting in the Welland River was the first known occurrence of EWC in Southwestern Ontario. At the time, EWC was just arriving in other parts of Ontario and the Great Lakes from Massachusetts, where it escaped a botanical garden after it was planted there in the late 1800s.
This aggressive invasive aquatic plant can reduce an area’s biodiversity by developing into dense floating mats that clog up shorelines and shade out native species. When EWC decomposes each year, it creates anoxic conditions, which negatively impact the reproductive and foraging conditions that are necessary for native fish species and species-at-risk like freshwater mussels.
Dense, thick EWC infestations can also make recreational activities like swimming, angling, and boating almost impossible. To top it off, their hard seeds with barbed spines accumulate on shores and can cause injury when stepped on, ruining an otherwise ideal beach day!
The ISC went out to the Welland River with Ducks Unlimited to assess the issue soon after the initial report. The proximity of EWC to the Welland Canal and the Niagara River intensified the likelihood of further dispersal into the Great Lakes, increasing the urgency to address this population.
“[The infestation] was isolated to a stretch of the river between the town of Wellandport and the city of Welland, and with that knowledge we also saw that the infestation was not quite a monoculture yet,” says Karen Alexander, Policy Coordinator at the ISC. “It was long, linear and established strands, but not really thick yet.”
From that info, ISC and partners determined that the EWC infestation could still be controlled with a rapid response. Without quick interference, this invasive plant could spread exponentially: one-acre of EWC can produce enough seeds in a single season to cover 100 acres the following year. And seeds from one plant can spread far and wide in an unpredictable manner; those from one area can get caught in the feathers of Canadian geese and similar waterfowl and hitch a ride to other wetland habitats.
“The sooner that you can stop that potentially from happening, the more likely you’re going to eradicate it,” says Alexander.
With support from the Ontario Ministry of Northern Development, Mines, Natural Resources and Forestry and the Ontario Federation of Anglers and Hunters (OFAH) Hit Squad Program, the ISC partnered with the Niagara Peninsula Conservation Authority (NPCA) to develop the EWC Rapid Response Program.
To stop seed production in the Welland River, five summer employees hired by the ISC and OFAH Hit Squad Team as a part of the Rapid Response Program were tasked with a specific mission: hand-pull EWC plants along 33 km of the river.
a) A summer student from the Hit Squad Team pulling an EWC plant from the Welland River.
b) A dense section of EWC in the Welland River
EWC is an annual plant. Annual plants grow from the previous year’s seed. By removing the plant before it produces seed, the population cannot sustain itself and the number of plants emerging each year will decline.
Using canoes and a small motorboat, the summer students set out five days a week between June and September 2022 to try to reach and dispose of each EWC plant that could be detected, with a focus on areas of the river with thick infestations.
The students started out spending about four hours a day paddling from public launches to infected areas, which was time that could be spent pulling instead. The ISC contacted the Township of West Lincoln, the Town of Pelham, the Township of Wainfleet, and the city of Welland to inquire about alternative methods of launching. In response, the municipalities mailed letters to riverfront landowners explaining the program.
Seven landowners offered the students access to their properties as a more convenient place to dock, have lunch, and as an emergency exit route. The joint efforts of the municipalities, the community, the ISC and the partners exemplify how vital teamwork was to the success of this program. And a success it was – by the end of the summer, the Hit Squad Team had pulled more than 7000 plants.
This initial control effort is a part of a multi-year response that aims to contain the population of EWC within four years. Containment efforts will be followed by a monitoring and maintenance program, since EWC seeds can survive and sprout for up to 10 years post-seeding. But by stopping most of the plants from going to seed in just this first year, there should be a much lighter pull next summer.
Recreational paddlers were also encouraged to ‘Paddle with a Purpose’ across waterways in Niagara. The NPCA and the ISC hosted two Paddling Tours in July 2022 to teach paddlers how to identify and report EWC observations.
“If someone can learn to identify water chestnut in the water, they’re now empowered to make these observations in the Welland River, or other tributaries in Niagara, or maybe other tributaries in Ontario,” Alexander explained in the ISC webinar series. “We really wanted to build that community science approach that was so successful in launching this rapid response in the first place.”
What can we take away from this success story? Learning the signs of invasive species and reporting something that looks unusual to you is worth it! A single report can spark a rapid response that can make the difference between a manageable population requiring reasonable resources and an established infestation of invaders that are there to stay.
