How did they get here and how do they spread?
Invasive species arrived in a number of ways and over a number of years. The first ones to Canada arrived by ship with the early explorers. Some of the first invasive species to Canada arrived in the 1600's - over 400 years ago! However, invasive species have been arriving ever since, spreading across Canada and leaving a trail of destruction in their wake.
There are a number of ways that invasive species get here: by boat, trains, airplanes, recreational vehicles, machinery or equipment, vehicles, or dispersal via wildlife, wind and water from nearby infested areas. Some invasive species were accidentally introduced, as contaminants in seed shipments for example, while others were intentionally introduced because of some perceived benefit without knowing that the species would be invasive.
Once here, invasive species thrive because they have arrived with few or no natural predators or other factors that would normally keep them in check back where they came from. Also, our native species have not evolved to cope with these new invasive species, and so quickly become overrun. Invasive species can spread locally quite easily but can also spread across the country in a relatively short time by the same ways that they got to Canada.