Invasive purple loosestrife (Photo by Mike Dembeck)

Invasive purple loosestrife (Photo by Mike Dembeck)

Invasive alien species 101

Dog-strangling vine (Photo by Couchiching Conservancy)

Dog-strangling vine (Photo by Couchiching Conservancy)

What are invasive alien species?

Invasive alien species are plants, animals and micro-organisms that are not native to an area but have been introduced to it, either intentionally or by other means (for example through ballast water or the trade of international goods).

True to their name, these introduced species often invade new habitats, out-competing native plants and animals and reducing biodiversity.

In fact, the International Union for the Conservation of Nature considers invasive alien species to be the second most significant threat to global biodiversity after habitat loss.

Why are invasive alien species harmful?

Invasive alien species:

  • destroy natural habitat and food for wildlife;
  • reduce agricultural productivity;
  • decrease property value;
  • increase costs for maintaining resources;
  • are potentially toxic to animals or cause allergies in humans;
  • destroy recreational opportunities and the aesthetics of the landscape.

How do invasive alien species spread?

  • in the fur or excrement of livestock and wildlife
  • on vehicles, ATVs, snowmobiles, boats
  • on the boots of hikers or in the wheels of bikes
  • in wind or water
  • in contaminated hay or in wildflower and bird seed mix
  • as “escaped” ornamental or food plants
  • in food imports

What is NCC doing to combat the spread of invasive alien species?

The Nature Conservancy of Canada (NCC) uses an integrated management approach that applies different techniques depending on the particular circumstances.

Various techniques used include:

  • mechanical methods such as pulling, mowing or haying;
  • grazing by livestock;
  • biological control — using the species' natural predator to combat the invader;
  • chemical control by trained professionals.

Depending on the situation, a combination of approaches may be necessary.

In every instance, the situation is studied carefully and options weighed, considering the impact of each method before they it is applied.

Once a strategy is implemented, NCC staff regularly monitor the area to see how effective the strategy is at reducing the population of invasive alien species and whether new methods may be required. 

Did you know?

Every single one of the 200 million European starlings found today in North America are descendants of approximately 100 birds introduced to New York City's Central Park in the early 1890s by a society who wanted to introduce all of the birds mentioned in the works of Shakespeare to North America.

The rapid increase in population sizes of the European starling resulted in the displacement of native cavity nesting birds such as eastern bluebird. Thankfully, while the eastern bluebird was listed as rare for many years, it has since recovered due to bird box programs.

Discover more about invasive species by visiting our invasive species gallery.

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