Invasive Species Awareness Day 2018: What you need to know

Grass carp
Grass carp is one species that threatens to take over the Great Lakes and they already prosper in streams in the US. U of T researchers are looking at ways to keep these, and many other non-native species, controlled and contained. (Photo by Peter Halasz)

Joseph Burrell

Our local ecosystem is teeming with invasive species. In fact, many of Ontario’s most common species are non-native, brought here by accident or on purpose.  

Plants in the fields, fish in our lakes and even worms in the ground that you’re most familiar with largely came from foreign ecosystems – introduced at the detriment of native species.

Ahead of the first annual GTA Invasive Species Awareness Day taking place at U of T Scarborough, writer Joseph Burrell spoke with a group of U of T environmental scientists who are experts on invasive species.

Stuart Livingstone…

is a postdoctoral fellow at U of T Scarborough. His research focuses heavily on the impact that Dog-Strangling Vine (DSV) has had on biodiversity and ecosystem functioning in Ontario.

Q: You mention that DSV has been here for over 100 years and went unnoticed until recently, do we know how DSV came to take over Ontario, why it wasn’t noticed, and where it came from?

Stuart Livingstone studying spread of invasive plants
Hypena caterpillars originate in Ukraine where DSV is a rare, native species.

A: DSV’s native range is in Eurasia, where it’s actually a rare species! Regarding its invasion in North America, it's suspected that the "lag time" before its invasion is due to a couple things: first, DSV populations are subject to "positive density dependence,” meaning that increasing abundance of DSV accelerates its growth. Second, DSV is a prolific colonizing species. Its seeds are dispersed great distances by wind and get blown along highways and train tracks. DSV tolerates harsh sun, deep shade, and nutrient depleted soil. The herbicide Glyphosate kills the plant, but it is extremely resilient to clipping and mowing.

From your time in horticulture retail, which plants make you think “those will be everywhere in 10 years,” when you see them at a garden center?

Great question. It's difficult to say exactly which species have the potential to become invasive. Scientists are working on this, but haven’t yet perfected methods to identify invaders before they become a problem. Examining the “functional traits” of introduced species, as they compare to native species, is showing the most promise as a predictive tool. But we should still be taking a precautionary approach.

A big challenge is that many urban residents want to plant a diversity of plants in their garden, which is great! But they want plants that have broad tolerances or are great "ground covers" and often that means they have invasive potential. The workshops at the Invasive Species Day will be discussing this stuff in detail!

Peter Kotanen…

Earthworm
Preventing earthworm spread is difficult due to the eggs' tendencay to stick to shoes and tires.

is an associate professor in the Department of Biology at U of T Mississauga. The species he focuses on include non-native Canada Thistle and Burdock, as well as Garlic Mustard and invasive earthworms in the lab.

We know how seeds from invasive plants can be transported on clothing while people travel, and how ballast tanks can move aquatic species, but how are worms being inadvertently relocated?

Seeds actually move in all sorts of ways! Most non-native worms probably reached North America in soil ballast on sailing ships, but new species are still arriving. It's unclear to me how this happens. Earthworms lay eggs in soil – and can even be moved in dirt stuck to car tires – this likely is the stage at which much movement occurs. Another major pathway is fishermen, who use worms as bait and in the process introduce them to new areas.

What species are these worms exactly, and what impact do they have on the populations they compete with?

We have around 20 worm species in Ontario. Only two are thought to be native – one is aquatic and the other is rare. All the worms you're ever likely to encounter in our soil are introduced. I'm not aware of competition between native and non-native worms; the native ones are just too scarce. But worms do have seriously negative effects on forest plants – both wildflowers and tree seedlings.

I don't know of any realistic way of controlling earthworms. There is increasing interest in reducing their further spread by, for example, discouraging or banning their use as fishing bait.

Sandy Smith…

Tree killed by emerald ash borer larvae
Ash Borers leave distinct trenches carved under tree bark and often kill the host plant.

is a professor who studies forest insects at U of T St. George – with particularly interest in the Emerald Ash Borer (EAB) – and the threat they pose to forest vegetation.

When was emerald ash borer first found to be a threat to in eastern North America and how did it end up here?

It was first noticed in 2003, and it likely arrived in shipping crates containing nursery stock imported from Asia.

Why is the emerald ash borer much more dominant in Europe and North America than it is in its native East Asia?

It is not really in Europe yet, just arriving in Moscow and moving west. It originates in Asia, where it has adapted with Fraxinus Mandschurica and other native Ash. They have a long evolutionary history together, but ultimately there’s much less ash composition there than in North America.

Can you talk about examples of successful invasive species bio control, either in the case of EAB or other pest species in Ontario?

There is no successful EAB biocontrol yet, or likely ever. Biocontrol agents only slow the spread and reduce the impact of the invasive target. They don’t eliminate, and in many cases don’t even prevent economic impact. Several good examples of ‘successful’ biocontrol are available but the closest to home is Purple Loosestrife, with methods listed on page 28 of this Invasive Plant Council report.

 

Nick Mandrak...

Nick Mandrak in his lab
From the time he was a child, Mandrak knew he wanted to study aquatic life, even writing "future ichthyologist" in his seventh grade yearbook.

is an expert on invasive aquatic species at U of T Scarborough. His research focuses on a number of species including various kids of Asian carp -- Grass, Bighead, Black, and Silver carp in particular. 

Why are Asian carps an important environmental issue?

Asian carps are a troublesome invasive species because they’re such voracious eaters. Silver Carp for example can eat a third of their body mass a day and can grow up to a metre long and weigh 50 kilograms (110 pounds). They basically displace native species because they eat all of the available food in a habitat. They also grow so large so quickly that they have no natural predators in North America. In some areas of the United States Asian carps already make up 95 per cent of the total weight of freshwater fishes.

What are some ways they can migrate into Canadian waters?

The most obvious route is by spreading into the Great Lakes. But they may also be introduced by anglers using them as illegal fishing bait or by people simply buying them in live fish markets and releasing them. I remember the first Asian carp I saw in Canada was found swimming in a water fountain just south of Queen’s Park. I was working on my PhD and we got a call from a security guard about a funny looking fish that someone had caught in the fountain. Turns out it was a Bighead Carp that someone had probably bought in a nearby live fish market and released into the fountain, most likely as a prank. It’s the same issue with Goldfish. People will just release them into the wild without thinking about the consequences.