The most pressing invasive species threatening Canadian habitat

Canadian wildlife

Global warming may be putting animal populations around the world at risk, but the second most dangerous threat might surprise you. After habitat loss, invasive species pose the single greatest threat to biodiversity worldwide.

With few natural predators and higher rates of reproduction, invasive species have the capacity to seriously damage their surrounding ecosystem, causing native species to expatriate and even become extinct. And while Australia usually bears the brunt of jokes about invasive species (remember The Simpsons episode where Bart unleashes toads on the country?), there’s no shortage of them in Canada.

Here are some of Canada’s invasive species, all of which pose a considerable threat to our country’s habitat and native animal populations.

Emerald Ash Borer

Photo courtesy of Herman Wong HM/Shutterstock.com

The Emerald Ash Borer was first detected in Windsor in 2002 and originated in eastern Asia. Extremely difficult to detect early, this invasive species has killed tens of millions of ash trees since its arrival. The larvae burrow through the inner bark while the young beetles feast on the leaves, effectively killing the ash tree. In banning the movement of firewood, provinces across Canada are hoping to stop the colonization of these pests.

Zebra Mussels

Zebra Mussels
Photo courtesy of 1082492116/Shutterstock.com

Zebra Mussels were first documented in Canada in the late 1980s. In just over 20 years, their presence has exploded throughout the Great Lakes.

A female mussel can produce more than one million eggs per year. The result is a population that has altered the food web dramatically, reducing populations of algae and plankton, which native species need to feed on.

Asian Carp

Asian Carp
Photo courtesy of Wikimedia Commons

Once established in an eco-system, these fish—which can grow to be more than 100 pounds—are virtually impossible to eradicate. Right now, the focus remains on preventing the fast-growing, aggressive, and highly adaptable species from entering the Great Lakes.

Asian Long-Horned Beetle

Asian long-horned beetle
Photo courtesy of Kyle Ramirez

Unlike some of the other species on this list, Asian long-horned beetles are not only foreign, they also look decidedly evil. Native to China, it’s believed that they first arrived on the outskirts of Toronto in 2003 via packaging materials.

Difficult to eradicate with no known predators, the beetles poses a substantial threat to Canada’s natural forests. Although they were declared eradicated in 2013—a process that included cutting down 27,000 trees at a cost of $33 million—these creepy insects are still popping up.


Photo courtesy of Thorney

Let’s call didymo for what it truly is—rock snot. With confirmed cases in Alberta, British Columbia, the Maritimes, and Quebec (where it has grown in fast-flowing cold water environments) the invasive species isn’t spreading as quickly as was feared. Still, it is putting fish populations at risk by making it more difficult for eggs to survive their incubation period.

Purple Loosestrife

Purple Loosestrife
Photo courtesy of Ivar Leidus

Invasive species typically reproduce faster than native ones, and the purple loosestrife is no exception to this rule. It’s been estimated that one plant can produce three million seeds.

Although this species, which looks similar to fireweed, is attractive, it chokes out native species including endangered indigenous plants. With little food value, it causes native animals to expatriate.

Round Goby

Neogobius melanostomus1
Photo courtesy of Wikimedia Commons

It may have a cute name and be diminutive in size, but this freshwater fish is still to be feared. In less than a decade it’s spread to all five Great Lakes, where in some areas there are more than 100 fish per square metre, dramatically altering the food systems. Worse, it’s also believed that the goby may be linked to outbreaks of botulism in fish and fish-eating birds.

Giant Hogweed

Giant hogweed
Photo courtesy of Rbk dolde

Not only is this Southwest Asian plant damaging to its surrounding habitat by shading out native plants, but it’s so dangerous that it can also make you go blind. No, really. The giant hogweed, which is becoming increasingly common in Southern and Central Ontario, contains toxins that can cause severe inflammation of the skin and even temporary blindness.

Eastern Grey Squirrel

Eastern Grey Squirrel
Photo courtesy of BirdPhotos.com

They may be cuter than some of the other species on this list (again, need we bring up the horrifying Asian long-horned beetle again?) but Eastern grey squirrels are considered one of the top 100 invasive species in the world. They displace native birds, compete with native mice and voles, and pose a threat to Garry Oak ecosystems by damaging and killing trees by stripping the bark.

Invasive Phragmites

Photo Courtesy of Christian Horz/Shutterstock

Phragmites are a part of the iconic wetland scenery; watching the breeze through this tall grass is a relaxing and hypnotic experience. Sadly, an invasive subspecies from Eurasia has been running rampant in Ontario, chocking out native species critical for the health of the wetlands. Not only does it out-compete other species for valuable nutrients and water, but it also releases toxins that can kill surrounding plant-life.

This invasive species has proved tricky to combat. Largely, this is due to the myriad of similarities with the native Phragmite. Generally, the invasive species grow taller (up to 15 feet), grow in dense clumps, and have tan stems compared to the reddish-brown stems of the native kind.