Invasive Alien Species – What Can We Do?

An interview with Catherine Kavassalis by Guest Writer: Rebecca Last-Guenette Member – Ottawa-Carleton Master Gardeners

Globalized trade brings us luxuries from around the world. Unfortunately, it can also bring us invasive alien species (IASs). For example, scientists believe the emerald ash borer (EAB – Agrilus planipennis) was introduced to North America via wooden packaging. Some plants, such as purple loosestrife (Lythrum salicaria L.) and Japanese honeysuckle vine (Lonicera japonica) were deliberately introduced as ornamentals in the 19th Century. Only more recently have we come to realize the damage they can do.

Every time we turn around, there seems to be a new invasive threat. I asked Master Gardener Catherine Kavassalis to help me sort Cathy is my idea of a Master Gardeners’ Master Gardener. More than just a passionate gardener and conservationist, Cathy is a former chemist and teacher. She did her doctoral work at M.I.T. and later received a masters in environmental education from the University of Toronto. She has taught and worked with not-for-profit organizations promoting biodiversity. Now she volunteers as an educator and inspirational speaker and an active member of the Halton Region group of Master Gardeners.

Catherine Kavassalis: Master Gardener, Founder of the Canadian Coalition for Invasive Plant Regulation (CCIPR)

RL: Cathy, thanks so much for agreeing to talk to me. I’d like to start by getting a better understanding of why we should worry about invasive alien species (IAS)?

Invasive Alien Species (IAS) are non-native species that do ecological and socio-economic harm. They spread easily and are difficult and expensive to control.

Ecological impacts include: disrupting essential ecosystem functions (e.g. loss of pollinators); changing organic litter, which leads to changes in soil formation, soil chemistry and soil organisms; and suppressing, displacing or extirpating native plant species.

Some invasive species, such as giant hogweed (Heracleum mantegazzianum) and wild parsnip (Pastinaca sativa) are serious threats to human health. Others threaten food production. All invasive species threaten our unique natural legacy.

Economic impacts include the costs of removing these species, and increased costs for food production, fisheries and lumber. IAS also increase the risks of fire, erosion, and property damage.

RL: I shudder when I think of an Ontario spring woodland filled with garlic mustard instead of trilliums! What new IAS threats keep you up at night, and why?
The globalization of trade and travel provides many pathways for invasive species to enter Canada. Climate change is projected to allow more potentially harmful organisms to survive here. That worries me.
On the immediate horizon are things like Spotted lantern fly (Lycorma delicatula), an asian planthopper that threatens production of grapes, stone fruits, and apples.  Oak wilt (Ceratocystis fagacearum) is also at the Ontario border. Like Dutch elm disease, oak wilt has the potential kill all oak in its path. Oaks are keystone species supporting more forms of life than any other tree genus in North America. That greatly worries me.

RL: At a recent gardening seminar, I learned that Canada’s regulations on IASs aim at limiting their economic damage. Given how much damage these species can do to ecosystems, do you think this approach is sufficient? What regulatory approaches do you think would work better?

Canada’s legislative approach to IAS is unfortunately fragmented. A nationally coordinated, multi-jurisdictional framework is badly needed. For instance, the horticultural trade has been identified as the largest pathway for the introduction of invasive plant species in Canada and yet little regulatory action has been undertaken to address the problem.

The newly formed Canadian Coalition for Invasive Plant Regulations (CCIPR) is calling for:

  • Effective pre- and post-border invasive species risk assessments;
  • Bans on the sale and movement of high risk invasive plant species;
  • Labeling to identify and educate the public about lower-risk invasive plants;
  • A verifiable industry-wide Code of Conduct;
  • Public education including alternatives to invasive plants (e.g. Plant Wise; Grow me Instead).

RL: Recently some garden clubs in the Ottawa area, including ours, adopted guidelines to discourage gardeners from donating invasive species to plant sales – a kind of “thanks but no thanks” list that accompanies the call-out for plant donations. What other measures can garden clubs take to help be part of the solution to IAS?

Garden clubs can support the CCIPR initiative. More news to come on that. Garden clubs can also share lists of alternative non-invasive species, particularly regionally appropriate native keystone species. (Visit Forest Gene Conservation Association for lists of appropriate trees and shrubs – They can help to spread the word about Jumping Worms and other soil borne invasive species; and garden clubs can ask the provincial government to restore funding to the Ontario Invasive Plant Council, an organization that has worked to develop “Grow me Instead” lists as well as “Best Management Practices” for addressing the invasive species we gardeners have helped to release.

RL: What about gardeners? Many of us are “plant-aholics” – always looking for new plants to add to our gardens. Are there measures that gardeners can take to minimize the risk that we are introducing  IASs to our neighbourhood?

When considering a new plant for your garden, do a bit of research.

  • Type the plant name into a search string and the word invasive, e.g. “yellow flag iris invasive” (It is best to use botanical names).  If you see hits that suggest it has invasive tendencies, put it back.
  • Avoid sharing aggressive non-native plants with friends and neighbours.
  • Take precautions when disposing of plant material and or soil.
  • Burn, solarize, tarp, chip, bury or drown if there is a risk to spread IAS.
  • Follow best management practices, BMPs.
  • If you are moving plants between locations, consider bare root planting to minimize movement of soils that can contain invasive seeds and or other invasive organisms.

Cathy, thanks so much for your wisdom on this important topic. You’ve helped us to better understand the magnitude of the threat and you’ve given us some strategies so that we can help become part of the solution, not part of the problem.


Cover Imgae: Government of Ontario Invasive Species Strategic Plan 2012

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