Non-native species are species that did not occur naturally within the local ecosystem until relatively modern times. Their arrival within the ecosystem was assisted by modern human activities and development. Non-native species can displace native species by out-competing them for space and food, by preying on susceptible native species or by introducing new diseases to native populations which have not yet evolved to fight off these diseases.

Here are some examples of introduced species which are harmful to native species in Cape Breton:

Plants - Purple loosestrife, a showy and beautiful purple flowering plant that chokes out native wetland habitat, was brought to North America as a garden plant and has since spread to many natural areas.

Mammals - The bobcat may compete with the native Canada lynx for food and habitat. It arrived on Cape Breton on its own when the Canso Causeway was being built in the 1950s.

Birds - The European starling is known to have a negative impact on native bird species elsewhere in North America. European starlings were released in the New World by Europeans and have spread over much of North America, including Cape Breton.

Fish - Rainbow trout and brown trout compete for food and habitat with the native brook trout and Atlantic salmon. Rainbow trout and brook trout were once stocked in lakes and rivers in Cape Breton and may also have escaped from fish farms.

Invertebrates - The common periwinkle has had an enormous impact on rocky coastal habitats all along the eastern seaboard. It has changed the natural habitat and altered the relationships between living things in intertidal areas. It was introduced in Nova Scotia probably unintentionally with ballast from ships.

Diseases - The brain worm Parelaphostrongylus tenuis is harmless to white-tailed deer but deadly to moose and caribou. It arrived with the white-tailed deer which expanded their range northward after humans cleared land for farming.

Beech bark disease is a fungus carried by an insect which disfigures and ultimately can kill beech trees. It was accidentally introduced to North America via Nova Scotia in the 1920s and has since spread throughout the Maritime provinces.