Invasive plant and animal species impact ecosystems around the world. For the London area, some particular plant species create a significant environmental and economic impact.
Brandon Williamson is a Land Management Technician with the Upper Thames River Conservation Authority (UTRCA), and he says that Buckthorn is one of the most prevalent invasive plant species in the London area. The main concern with Buckthorn is its allelopathy.
“This means that they release a chemical from their root systems into the soil that can prevent other species from germinating, and they can stunt the growth of other species,” he says. “Buckthorn is so pervasive on the landscape that that allelopathy – when it gets in the soil – can actually change the soil chemistry for many, many years.”
Williamson highlights the importance of patience. “When you go to remove Buckthorn from a site, to restore it to that native composition, you really have to be patient because sometimes those native species you replant may not grow and respond as quickly to that planting as on other sites, because the soil still has some of that chemical in it, and it can take many years for that to get out of the soil.”
Another problematic invasive plant species for London is Phragmites. “Every roadside and ditch within London, you’ll see that tall grass which is brown this time of year, with a feathery seed head to it,” Williamson says. “There’s many agencies that label it “The World’s Worst Invasive Species.””
He says Phragmites can completely choke out all other native species, including frogs and turtles, making it very difficult for them to move around.
Cathy Quinlan is a Terrestrial Biologist with the UTRCA, and she says Phragmites can be costly to eliminate. “The only way to control it is a series of cutting it at the right season, and then spraying the regrowth at a certain time of year. Sometimes these big areas where it just goes on for acres, they’ll roll it flat with a machine, then burn it, and then spray it. It’s a really expensive one to control.”
Quinlan stresses the importance of recognizing the economic impact of invasive species. “If we can nip these things in the bud before they get to be the big, widespread problem that they are now, that’s so much more cost-effective,” she says. “But it’s really hard to get governments and agencies to commit that money at the front end, because [the invasive species] isn’t there, so they just let it be, and then it multiplies the cost afterwards.”
