Invasive Species, Pests and Pathogens

What is a pest?

A pest species is any plant, animal, or other organism that can spread and, at least in some years, can threaten biodiversity, the economy, or society. It may or may not be a native species. Some native species are considered pests because of their impacts on forestry, agriculture, or other industries.

Examples of native pest species in the NWT include the spruce budworm, which feeds on spruce buds and needles and can threaten timber supply, or the raspberry fruitworm beetle, which can impact food crop productivity.

Spruce budworm (Choristoneura fumiferana) - Photo Credit: Government of the Northwest Territories

What is a pathogen?

A pathogen is a biological agent that causes disease. This includes viruses, bacteria, fungi, and parasites. Although pathogen infection and diseases are a normal part of any ecosystem, they can sometimes cause significant die-offs in wildlife, and some diseases can infect people or domestic plants and animals. It is especially concerning when pathogens are introduced or spread into new areas, as they can have devastating effects on populations that have no natural immunity.

Examples of common pathogens in the NWT include the tapeworm Echinococcus canadensis that causes hydatid disease in moose and caribou or the fungus Chrysomyxa weirii that causes spruce needle rust. An example of a non-native pathogen in Canada is the fungus Pseudogymnoascus destructans, which causes white-nose syndrome in bats.

Spruce needle rust (Chrysomyxa ledicola) - Photo Credit: Government of the Northwest Territories

What is an invasive species?

When a plant, animal, or other organism is introduced by human action outside of its natural range, it is called an alien species. An invasive species is an alien species whose introduction or spread threatens biodiversity, the economy, or society. Invasive species tend to thrive in disturbed areas, spread rapidly, and may negatively impact native species. Many invasive species have been introduced to North America from Europe and Asia.

Examples of invasive species in the NWT include white sweet clover, a plant originally from Eurasia that spreads along roadsides and river shorelines, or the amber-marked birch leaf miner, an insect introduced from Europe that now impacts many of our wild birch trees.

White sweetclover (Melilotus albus) - Photo Credit: Michael Oldham

What about range-shifting species?

As climate and land use change, some species are shifting or expanding their ranges. For example, warmer winters in combination with fire suppression have allowed the mountain pine beetle, native to British Columbia, to expand into some areas of Alberta. The mountain pine beetle was even observed in the NWT in 2012. While such species are indeed expanding beyond their historical range, they are doing so without the help of direct human action. Therefore, a more appropriate term is neonative species.

Other examples of neonative species in the NWT include white-tail deer and magpies, which are expanding their range northward from the southern NWT.