Indicator: Forest insects

In 2016, 15.5 million hectares (ha) of forest were affected by insects in Canada.

  • This represents a 1.5% decrease in area affected over the previous year.
  • Growth of the spruce budworm outbreak in Quebec has slowed.
  • Nationally, the area affected by forest tent caterpillar has decreased, but the area affected annually in Ontario increased from only 28,000 ha in 2012 to 1.1 million ha in 2016.
  • The area affected by mountain pine beetle continues to decline.
  • The outbreak of western spruce budworm in British Columbia’s Douglas-fir forests has now ended.
  • Insects are one of the most important disturbance agents in Canada’s forests.
  • Outbreaks of some key species like spruce budworm and forest tent caterpillar are cyclical.
  • Bark beetles tend to erupt under a particular set of forest and climatic conditions.

Forest area containing defoliated trees for four insects in Canada, 2006–2016


Graph data
Table displays the area disturbed in hectares by western spruce budworm, mountain pine beetle, forest tent caterpillar and eastern spruce budworm for each year between 2006 and 2016.
Year Western spruce budworm Mountain pine beetle Forest tent caterpillar Eastern spruce budworm
2006 776,907 9,243,408 5,564,624 1,105,221
2007 865,023 10,051,919 2,210,536 1,350,369
2008 804,711 7,841,993 1,568,128 876,115
2009 796,904 8,953,441 154,243 831,937
2010 503,014 6,251,586 220,651 1,510,074
2011 623,426 4,624,907 594,647 1,492,829
2012 456,745 3,016,228 729,874 1,792,062
2013 128,037 2,973,935 7,464,898 2,777,998
2014 44,608 2,208,687 5,907,787 3,583,700
2015 9,135 1,447,954 4,841,071 5,235,854
2016 3,426 376,669 4,013,393 4,970,951

Why is this indicator important?

  • Insect outbreaks are second only to wildfires in the impact they have on Canada’s forests.
  • Monitoring multiple species is important because they often have synergistic and interrelated effects. Some species defoliate and weaken the trees, while others tend to attack and kill previously weakened trees.
  • Because insect growth rates are directly tied to environmental temperatures, insects are sensitive indicators of climate change at both local and continental scales.

What is the outlook?

  • The slowing of the spruce budworm outbreak in Quebec is a positive development, but the outbreak may still spread into Atlantic Canada’s large areas of susceptible spruce-fir forest.
  • Mountain pine beetle continues to spread in Alberta, and its eastward movement into Saskatchewan and beyond remains a concern.
  • The outlook for the current spruce beetle outbreak in British Columbia remains highly uncertain. It will likely depend on cumulative drought stress in susceptible spruce forests.

What reporting frameworks does this indicator support?

Sources and information
  • BC Ministry of Forests, Lands and Natural Resource Operations. 2016. 2016 summary of forest health conditions in British Columbia [10.2 Mb PDF].
  • National Forestry Database. Forest insects, Table 4.1 Area of moderate to severe defoliation (including beetle-killed trees) by insects (accessed July 3, 2018).
    • 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.
    • Percent change value for the area impacted compared to the previous reported year (2015) uses data corrected after the publication of the 2017 report; the 2015 value for total area defoliated by insects was 15.7 million ha.