She stripped a river full of this pesky invasive plant — by hand

Katie Church has yanked so many patches of the pesky invasive European water chestnut this summer, she has dreams about doing it.

"I look at the chestnut in the water and [dream of] removing it and making sure everything is clear," she laughs.

Church has just finished leading a field team of five summer students hired by the non-profit Invasive Species Centre. The group was tasked with searching, finding and plucking the thick, rooted green invasive aquatic plant by hand along a 30-kilometre stretch of the Welland River, in Ontario's Niagara Region.

"It's a lot of work, especially when you get into those big patches, and everywhere you look, there's chestnut and all you want to do is remove it," said Church, a recent graduate of the ecosystem restoration program at Niagara College.

European water chestnut (EWC for short) clogs shorelines, cutting off sunlight and space for fish and native plants. It's also a nuisance for humans — difficult to swim or paddle through. Its sharp, spiky seeds can puncture skin and even poke through a thin sandal.

When Church started her work in July, huge swaths of the river's edges were covered in EWC — nearly 100 per cent cover in some spots. In eight weeks, the team hand-pulled an estimated 7,000 plants, filling 70 of those plastic tote containers.

Pulled plants were taken far from the water to die as quickly as possible — dried out, turned into green fertilizer and composted properly.

During her final day on the water last week, Church scanned both sides of the river, honing her now-expert eye in on the floating aquatic plants. She saw lots of lily pads and water-milfoil, but no EWC.

"I'm very proud of our team and what we've been able to accomplish," she said. "It's a really great feeling to just fly by and be really confident that there's nothing."

3 known populations in Ontario

The Welland River is one of three known EWC populations in the province. The annual plant is also found around Wolfe Island, near Kingston, and at Voyageur Provincial Park on the Ottawa River, according to the Invasive Species Centre, based in Sault Ste. Marie, Ont.

Colin Cassin, the centre's policy manager, is not sure how the plant got to Welland. EWC travels primarily through its seed moving around, so he suspects maybe a bird picked it up or it came from a contaminated boat.

"We're right at the nexus here between established and early introduction," he said. "This is the best-case scenario in terms of getting ahead of it."

He credits early detection. A local kayaker first spotted something strange on the river in 2020 and reported it. It turned out to be EWC, which was mapped out in 2021. The field team hit the water for the first time this year.

• LISTEN | CBC's Haydn Watters hits the water with a team searching for European water chestnut:

Cassin said working in invasive species is often doom and gloom. But he's confident this work in Welland is on the rare path to success — leading to the long-term removal of EWC from the river.

"We hope that next year, by stopping most of these plants from going to seed, we're going to be able to have a much lighter pull," he says, hoping for at least a 50 per cent reduction.

"If we can stop it from going to seed this year, in theory, we've won."