Terrestrial Invasive Species
Invasive species have been spreading across the landscape of Ontario since the beginning of European colonization. Many have arrived accidentally, in ships’ ballast or stowed away in baggage and freight. Others have been introduced deliberately, sometimes for reasons that now seem very odd.
The common or European starling is the result of one of the more curious efforts to introduce non-native species to North America. Their presence here is said to be the result of persistent efforts by lovers of William Shakespeare to introduce all of the birds identified in his written works. Now an abundant species over much of the continent, they have had significant negative impacts on native hole-nesting species such as Eastern bluebirds and red-headed woodpeckers.
Common buckthorn is an invasive plant species that was introduced in the 19th Century as an ornamental shrub and windbreak. It is now known to be an important host species for agricultural species and an aggressive competitor with native plant species. Garlic mustard escaped from kitchen gardens where it was drown as a food plant and is now a serious threat to a variety of native plants, including trillium, Ontario’s provincial plant.
Some introduced plant species have not themselves proven to be invasive but have carried invasive organisms with them. Several native Ontario plant species are now at risk of disappearing from the landscape because they have no resistance to fungi that came to North America on imported plants.
Disease-causing organisms that affect wildlife and humans can also be introduced. The West Nile virus appeared in Ontario in 2001 and has spread rapidly to other parts of the country.
Natural expansion of species beyond their historical range typically occurs over long periods of time; however, humans can and do contribute to the rapid spread of invasive species. Invasives can be introduced and spread in a variety of ways including untreated packing materials, on imported plants, in baggage, on hiking shoes or in the pet and agricultural trades.