Alien and introduced species

Presence of alien and introduced species




Plants, animals and microorganisms introduced outside their normal range by humans are considered introduced alien species. Not all alien species are harmful to an ecosystem, and some are introduced on purpose (e.g., for conservation, in gardens, to increase hunting or fishing opportunities, etc.).

Invasive species are alien species whose introduction has an environmental, economic or social cost. (CBD Secretariat n.d.). The impacts of invasive species include loss of biodiversity, reduced property value or reduced quality and abundance of resources to humans, including loss of plants traditionally used by First Nations.

Increases in resource exploration and development and increases in backcountry pursuits will likely increase the range and number of invasive species. A changing climate is also a factor in the increase and spread of alien and invasive species (Streicker 2016).



Earliest and most recent introductions


Common Plantain. Bruce Bennett.


New introductions come from gardens.


The earliest report of an introduced species was a collection made by William Healey Dall in about 1868 along the Yukon River. He collected Common Plantain (Plantago major), a species known for its medicinal properties that could have been introduced by early traders.

In 2016, several species are newly reported and have been added to the list of exotic species. These include Ground-ivy (Glechoma hederacea), a garden weed, and two species Creeping Bellflower (Campanula rapunculoides) and the berry-producing shrub Cotoneaster sp. that have escaped gardens and are establishing wild populations.



What is happening?




  • As of November 2016, an estimated 166 alien plant species have been identified in Yukon. Of these, 99 are currently believed to be present, 32 are believed to be absent, and the presence of 37 additional species is unknown (Figure 1).
  • Twenty of these plant species are considered invasive in Yukon (Yukon Invasive Species Council n.d.)
  • Since 2015, a number of vascular plant species once thought to be introduced are now considered to be expanding their range and are therefore considered native. Changing species range is natural and the rate of expansion appears to be increasing. This phenomenon has been more clearly documented with vertebrate animals sure as Mule Deer, Cougar, and Moose which have expanded their range northwards. Several species are newly reported and have been added to the list of exotic species. These include Ground-ivy (Glechoma hederacea), a garden weed, and two species Creeping Bellflower (Campanula rapunculoides) and the berry-producing shrub Cotoneaster sp. that have escaped gardens and are establishing wild populations.
  • Since the late 1800’s, botanists have searched communities collecting and identifying plants. With few exceptions, introduced plant species are associated with human disturbance. By looking at the results of surveys in the communities (particularly Dawson City and Whitehorse), along major highways (particularly the Alaska and Klondike highways), and along major rivers (such as the Yukon and Teslin river), a trend in the number of introduced species naturalized is shown (Figure 1).
Figure 1: Introduced plant species persisting in Yukon
Source: Yukon Conservation Data Centre, 2015.




  • There are 72 regularly occurring mammal species in Yukon; of these, three are introduced beyond their native range.
  • No mammals are considered invasive in Yukon.
  • The House Mouse is an alien species from Europe that was introduced accidentally or has spread from southern populations.
  • Feral horses are known to be present in Yukon at the time of this report.
  • Elk, though native to southeast Yukon, were introduced to south-central Yukon in the late 1940s, to reduce hunting pressure on moose and caribou.
Elk. J Bergold.




  • There are four introduced bird species out of the 240 bird species that regularly occur in Yukon: Rock Pigeon, House Sparrow, Eurasian Collared Dove, and European Starling.
  • These species were introduced accidentally or have spread from southern populations.
  • These four species occur in low numbers and are not expected to have a large impact on native species (Yukon Invasive Species Council n.d.).
House Sparrow. Cameron Eckert.


Freshwater fishes


  • Most Yukon lakes and waterways appear to be free of invasive or introduced species.
  • Out of the 38 regularly occurring species of freshwater fish, two are introduced:
    • Goldfish is an alien species that occurs in Yukon and was either introduced accidentally or spread from southern populations.
    • Threespine Stickleback is native in B.C. and Alaska but was accidentally introduced into two pothole lakes with fish stocking programs in the 1970s.
  • Several fish species, though native in some rivers or lakes in Yukon, were intentionally released in other areas to enhance fishing opportunities (Table 1).
Table 1: Native Yukon fish species introduced to other places in Yukon
Species: Native to: Introduced in:
Arctic Char Two lakes in Ivvavik, northern Yukon Southern Yukon
Bull Trout / Dolly Varden Yukon and Liard drainages Pothole Lakes
Kokanee Alsek drainage Scout Lake
Rainbow Trout Alsek drainage Yukon River




  • Less is known about alien invertebrates in Yukon.
  • The Conservation Data Centre currently has about 3,000 invertebrate species recorded in their database; 26 are known to be introduced and believed to be present. It is likely that more introduced species are present but not detected.
  • There are several alien earthworms that are believed to live year round in Yukon (i.e., the night crawler or dew worm). The Red Wiggler is commonly used for composting, but is not known to overwinter in Yukon outside cultivation.
  • The Seven-spotted Lady Beetle is commonly used to control aphids in greenhouses and has been found in remote places such as Keno Hill. It is now believed to be persisting in the wild.


Seven spotted lady beetle. Kelcy Tousignant.


Taking action

The Yukon Invasive Species Council works to address the threats posed by invasive species through prevention, early detection and rapid response, control and management, research, and education. Council members come from different governments, industry and the public.

The Fisheries Program at the Department of Environment asks Yukoners to report aquatic invasive species. They actively promote information at boat launches throughout the Yukon.


Threespine Stickleback. NOAA Fisheries, Auke Bay Laboratories.


Data quality

  • Through the Spotter’s Network, there is a formal protocol for invasive alien species data collection within Yukon.
  • The Yukon Conservation Data Centre makes data publicly available to anyone wishing to access information on species or ecosystems of conservation concern. This includes lists of species, range maps and identification guides.
  • The Department of Environment provides additional information about Yukon’s aquatic invasive species and invasive plants.



Convention on Biological Diversity (CBD) Secretariat. n.d. Invasive species [cited 2016 Mar 3]. Available from www.cbd.int/invasive

Streiker, J. 2016. Yukon Climate Change Indicators and Key Findings 2015. Northern Climate ExChange, Yukon Research Centre, Yukon College, Whitehorse, Yukon, Canada. Available from: https://www.yukoncollege.yk.ca/research/abstracts/indicators.

Yukon Conservation Data Centre. n.d. Rare species database [modified 2015 Dec 23; cited 2016 Mar 3]. Available from: www.env.gov.yk.ca/cdc

Yukon Invasive Species Council. n.d. Yukon Invasive Species [modified 2016 Feb 20; cited 2016 Mar 3]. Available from: http://www.yukoninvasives.com/index.html