Biodiversity, Invasive Species, Wetlands

Space Invaders 101

What you need to know about invasive species

By Linda Browne May 20, 2026

Yellow warbler perched in an invasive phragmites stand.

At first glance, a field of purple loosestrife in full bloom can look stunning — a sea of vibrant violet flowers swaying along a wetland’s edge. But looks can be deceiving.

This pretty plant is a highly destructive invasive species in Canada, quietly crowding out the native plants that ducks, birds and other wildlife depend on for food and shelter.

During Invasive Species Action Month, we aim to spread awareness, and not invasives. This year’s theme, “Do It Yourself. Stop Invasives Together”, is a call to action and a reminder that small steps can add up to big results for Canada’s wetlands and wild spaces.

What are invasive species?

An invasive species is an organism, such as a plant, animal or microorganism, that is introduced, intentionally or accidentally, into an environment where it does not naturally occur. While many introduced species do not cause problems, some spread rapidly and become invasive, displacing native species and causing harm.

Why are they bad news for wetlands?

Wetlands are among Canada’s most productive and biodiverse ecosystems. They’re also the kind of environment where invasive species can spread quickly. The damage they cause is significant:

Purple loosestrife invades wetland habitats, choking out native plants and leaving less food for waterfowl and other wildlife. It also produces dense stands that reduce the quality of nesting habitat.
Invasive phragmites grows into dense thickets (sometimes reaching up to 20 feet tall) that crowd out native plants and animals, block access for wildlife like turtles, disrupt water flow and degrade shorelines and waterways.
Common carp, an invasive fish species, stirs up sediment and uproots aquatic vegetation, degrading the plant life ducks and other birds rely on for food and shelter.

How do invasive species spread?

Invasive species often spread through everyday human activities, many of them completely unintentional. Seeds and plant fragments can hitch a ride on boots, clothing and outdoor gear. Aquatic invasives cling to boats, fishing equipment and waders and get carried from one water body to the next. Firewood moved between locations can transport forest pests. Even pets and aquarium fish released into the wild can become invaders.

What you can do to stop the spread

When it comes to invasive species, policy and regulation, along with co-ordinated large-scale management and early detection/rapid response, is crucial to winning the battle.

In addition, one of the best defenses against invasive species is an informed, engaged public. Here are a few ways that you can make a real difference:

Clean your gear. After outdoor activities like hiking, boating, fishing or ATV riding, clean, drain and dry all of your equipment. When boating, fishing or hunting, remove visible plant material and mud, drain all water from boats and gear, and let everything dry completely before moving to a new location.
Choose native plants. If you’re gardening or landscaping, read up before you dig in. Use native plants (check out these regional guides) and avoid purchasing plants known to be invasive in your area.
Don’t let it loose. Never release aquarium fish, plants or pets into the wild (learn more here). What thrives in a tank can devastate a local ecosystem.
Spot it and report it. Learn to identify common invasive species in your region and download apps like iNaturalist to log sightings. The sooner an invasive is found, the easier it is to manage.

Mass of common carp at exclusion structure, Delta Marsh, Manitoba. © DUC

Spotted an invasive species? Here’s what to do:

If you think you’ve spotted an invasive species on your property or in your neighbourhood, don’t panic, but don’t ignore it either. Instead:

Take a photo and note the location.
Report the sighting using apps like iNaturalist or contact your provincial invasive species reporting line.
For small infestations of invasive plants on your own property, you may be able to remove them yourself, but it’s important to follow regional best management practices to avoid spreading them further. Check with your local authority’s best management practice guide first to make sure you’re removing them correctly and disposing of plant material safely.
Contact your local conservation authority or provincial invasive species council for guidance and support.

Together, we can stop the spread.

Invasive species are one of the leading threats to Canada’s wetlands and biodiversity, but they’re a threat we can fight together. This Invasive Species Action Month, take the pledge to be part of the solution.

Invasive species are changing the Canadian landscape

We’re using our expertise and experience to protect vital ecosystems from the threats posed by invasive species.

Learn more

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