Canada has an impressive array of native plant and animal species. They are not alone, however, as numerous others have been introduced – deliberately or accidentally – over several centuries.
Referred to as invasive species, introduced plants and animals pose a significant risk to biodiversity by out competing for resources, predation, introduction of disease, all of which may be irreversible.
Some, like the Rock Pigeon (Columba Livia), were introduced to Canada intentionally. In the early 1600s, Samuel Champlain brought them with him to add a European feel to New France. Two other common species of birds seen on the campus are also introduced from Europe and they are the House Sparrow and the European Starling. These three introduced species of birds are year-round residents on the campus. The Starlings, House Sparrows, and Pigeons all use the campus buildings to nest on, especially the abandoned portion of Brittain Hall.
The Cabbage White (Pieris rapae), a butterfly from Europe, was accidentally introduced to Quebec in the 1860s and has since spread throughout North America. If you see a little white butterfly, it’s usually a Cabbage White and they’re a real agricultural pest for plants in the brassica family like broccoli and cabbage. The Honey Bee was also introduced from Europe.
An estimated 5,000 non-native plant species have been introduced and established and now exist in North America. On the green lawns of the campus you can identify many species of plants that have been introduced from Europe and many of them are naturalized and form an important part of the functioning ecology of the area. Much of the information we have about the uses of some of these plants comes from Europe. Common Dandelion are a great example because they were introduced from Europe and have many edible and medicinal uses. In the mid-1600s, European settlers brought the common dandelion (Taraxacum officinale) to eastern North America and cultivated it in their gardens for food and medicine. Since then, it has spread across the continent as a weed. With many heads of 150-200 fruits each, a plant easily produces 1000-2000 seeds a year. In the warm part of the year the campus fields are often covered in dandelion flowers.
European Buckthorn is another invasive species which is native to Eurasia. It was introduced to North America as an ornamental shrub for fencerows. Because of its tolerance of a wide range of moisture and light conditions, along with its prolific seed production, European buckthorn is able to successfully invade many habitats. Animals and birds have adjusted to making use of it in these scenarios. A City of Montreal study found that White-tailed Deer on the West Island were found to be consuming parts of the tree at rates that were up to 25% of their diet. American Robins often eat the berries in the winter after most other berries have been eaten or rotted away.
Some introduced species can decimate or cause the near extinction of other native species. One recent example is the Emerald Ash Borer that has become established accidentally after being brought over in ships from Asia. The larvae of Emerald Ash Borer have almost killed all the ash trees in the West Island in the last ten years. The cost of removing and replacing urban street ash trees at risk in Canada was estimated to be around $1.3 billion to the year 2035 should no regulation occur.
After habitat loss, invasive species are considered the second greatest threat to biodiversity.