Photo: Creeping Thistle. This invasive plant is making its appearance in parts of the NWT (Lmmahood /Wikimedia Commons / CC BY-SA 3.0) Photo: Creeping Thistle. This invasive plant is making its appearance in parts of the NWT (Lmmahood /Wikimedia Commons / CC BY-SA 3.0)

First Symposium on Pests, Pathogens and Invasive Species in the NWT

There are invaders in the NWT!  Invasive species, that is –plants and animals that are not native to an area but arrived from somewhere else.  These out-of-place species –or “alien” species are considered invasive if they cause harm to the environment, economy or society. 

Invasive species tend to spread and invade habitats quickly.  When that happens, they can compete with native plants and animals, and, as a result, some native species may be reduced in number or even disappear.  In addition to the potential harm to an area’s biodiversity (variety of living things in an area), invasive species can change natural habitats or ecosystems.  In fact, invasive species are the second most important threat to native ecosystems, habitats and species after habitat change and degradation. 

Our northern climate prevents many alien species from establishing themselves in NWT’s ecosystems.  However, with climate change and other factors, this may be changing. Changes in the northern environment may favour the advance of alien species into our ecosystems . Examples of invasive species introduced to the NWT to date include sweet clovers (a type of plant) and amber-marked birch miners (a type of insect).  

Photo:  White Sweet Clover can take over naturally disturbed habitats and is found in many places in the NWT.  Wikimedia Commons / CC BY 3.0

Many northern communities have expressed concern over the potential effects of invasive alien species in their communities.  This spring, the Government of the Northwest Territories (GNWT) and partners, including the WRRB, are planning a conference on invasive species, pests, and pathogens in northern ecosystems. 

Pests can be native or alien species that can spread, and at least in some years, can threaten a component of an ecosystem, often with economic value.  Like the spruce budworm and forest tent caterpillars, pests are troublesome and may cause harm to plants or animals, humans or human concerns including forestry, crops, or livestock.  Insect pests that include aspen serpentine leafminer, willow blotch leafminer as well as tent caterpillars can cause forest defoliation –stripping trees of their leaves and in some cases, killing the trees and damaging forests. The birch leaf edgeminer, an alien insect species first noted in the NWT in 1994, and introduced from Europe, is considered both an invasive species and a pest species, turning trees in wild birch stands brown in mid-summer. 

Spring birches (Susan Beaumont, WRRB)  Birch leafminers are among the most common insect pests affecting birch trees in North America.  They are called “miners” because they feed inside the blade of a leaf by first digging a “mine” into these tissues.  These insects’ larvae consume areas inside the leaves affecting the leaves’ ability to produce food.  Yearly browning of birch leaves are noticed in mid July and August, but the leafminers have been feeding inside the leaf tissue since early spring. 

A pathogen is something that is infectious, such as a virus or bacteria, which causes a disease.

The upcoming symposium on Pests, Pathogens, and Invasive Species will bring people together to learn more and share information and approaches for responding to these threats to NWT ecosystems.  The NWT is establishing a council to help prevent the spread, help control, monitor, and then take action on pests, pathogens, and invasive species in the NWT.  Participants can help set up the council for the future as well as learn what they can do to help and take action. 

The conference will be held on April 9-13, 2018 at the Explorer Hotel in Yellowknife and will include presentations, posters, side events, and a talking circle. You can view a draft agenda and register at For those who would like to present or submit a poster, the deadline for submitting an abstract is January 31.

Fact Box:

  • Alien species are animals and plants introduced by humans, sometimes unintentionally, in areas outside of their natural range. Many alien species found in the Northwest Territories (NWT) have been introduced from areas as far away as Europe and Asia. 
  • Changes in the number of alien, invasive, or pest species of insects and spiders in the NWT provide an indicator of ecosystem change, including habitat and climate change.
  • NWT residents can help determine the current distribution of alien species in the NWT by reporting their presence to ENR offices.
  • Help stop the spread of invasive plants and insects in the NWT. Report “out-of-place” species by contacting or