Indicator: Forest insects

In 2015, 17.6 million hectares (ha) of forest were damaged by insects in Canada.

  • This was a 13% decrease in area damaged from the previous year.
  • Large increases in the size of the spruce budworm outbreak in Quebec were more than offset by decreases in the area affected by aspen defoliators in Alberta and British Columbia.
  • The area affected by bark beetles continued to decrease overall.

Defoliating insects can both weaken and kill healthy trees, while bark beetles often attack trees already under stress. Monitoring trends in both insect groups allows researchers and forest managers to gauge the impact of insects on wood supply and forest health.

Defoliating insects

  • In 2015, the spruce budworm epidemic continued to grow, nearly doubling in extent to 6.7 million ha.
  • In the same year, forest tent caterpillar populations and a suite of other aspen defoliators declined significantly in western Canada.
Forest area containing defoliated trees for three insects in Canada, 2005–2015
Graph displaying the area disturbed in hectares by western spruce budworm, forest tent caterpillar and eastern spruce budworm for each year between 2005 and 2015.
Graph data
Table displays the area disturbed in hectares by western spruce budworm, forest tent caterpillar and eastern spruce budworm for each year between 2005 and 2015.
Year Western spruce budworm Forest tent caterpillar Eastern spruce budworm
2005 463,962 3,160,818 721,471
2006 776,907 5,564,624 1,105,221
2007 865,023 2,210,536 1,350,369
2008 804,711 1,557,943 876,115
2009 796,904 154,243 831,937
2010 503,014 220,651 1,510,074
2011 623,426 594,647 1,492,829
2012 456,745 729,874 1,792,062
2013 128,037 7,464,898 2,777,998
2014 44,608 5,907,787 3,533,643
2015 9,135 5,199,101 6,726,007

Bark beetles

  • Mountain pine beetle populations in British Columbia continue to decline.
  • The distribution of mountain pine beetle in Alberta’s pine forest continues to be extensive. Populations are fluctuating regionally, and beetles are continuing to spread slowly eastward.
  • Populations of balsam bark beetle and spruce beetle are relatively high in British Columbia, with 2.3 million ha of balsam bark beetle and 194,000 ha of spruce beetle mapped in 2015.
Forest area affected by mountain pine beetle in Canada, 2005–2015
Graph displaying the area disturbed in hectares by mountain pine beetle in British Columbia for each year between 2005 and 2015.
Graph data
Table displays the area affected in hectares by mountain pine beetle in Canada for each year between 2005 and 2015
Year Area affected (hectares)
2005 8,736,068
2006 9,243,408
2007 10,051,919
2008 7,841,993
2009 8,953,441
2010 6,251,586
2011 4,624,907
2012 3,016,228
2013 2,973,935
2014 2,208,687
2015 1,447,954

Why is this indicator important?

  • Insects are one of the most important agents of disturbance in Canada’s forests.
  • Their feeding can either kill trees directly or seriously reduce trees’ health and productivity.
  • Because insect populations are sensitive to both average and extreme temperatures, they are important indicators of climate change in forest ecosystems.

What is the outlook?

  • The spruce budworm outbreak in Quebec is expected to continue increasing and spreading into additional areas in Ontario, New Brunswick and the rest of Atlantic Canada.
  • Mountain pine beetle continues to increase in Alberta, and its eastward spread into Saskatchewan and beyond remains a concern.
  • The spruce beetle outbreak in British Columbia is expected to continue increasing in both extent and severity.
Sources
Notes
  • Forest area disturbed by defoliators includes only areas with tree mortality and moderate to severe defoliation. Defoliation does not always imply mortality. For example, stands with moderate defoliation often recover and may not lose much growth.
  • Defoliation is mapped on an insect species basis, and a given area may be affected by more than one species at a time. This may result in double or triple counting in areas affected by more than one species, exaggerating the extent of the total area defoliated.