How does disturbance shape Canada's forests?

This graph shows the trends in forest area, in hectares, defoliated by five forest insects from 2010 to 2020. The insects are spongy moth, eastern spruce budworm, jack pine budworm, mountain pine beetle and spruce beetle.

The forest area disturbed by the spongy moth remained relatively low until 2019, when it slightly increased to about 50,000 ha. In 2020, the area disturbed increased significantly to a decadal high of nearly 600,000 ha.

The forest area disturbed by the eastern spruce budworm increased steadily from about 1.5 million ha in 2010 to about 5.2 million ha in 2015. In 2016, the forest area disturbed dropped slightly to about 5 million ha, but then increased to almost 6 million ha in 2018. In 2019, it decreased slightly again to about 5.5 million ha, then increased to the 10-year maximum of nearly 7 million ha in 2020.

The forest area disturbed by the jack pine budworm remained relatively low from 2010 to 2015. In 2016, it increased slightly to about 200,000 ha, after which it continued to increase to the 10-year high of about 3.7 million ha in 2020.

In the last 10 years, forest area disturbed by the mountain pine beetle has continued on a downward trend, from a high of about 6.2 million ha in 2010 to less than 200,000 ha in 2020.

The forest area disturbed by the spruce beetle remained relatively low from 2010 to 2013. In 2014, the area disturbed increased to about 340,000 ha, then decreased slightly until 2017 when it increased again to about 507,000 ha. After a slight decrease in 2018, the area disturbed remained relatively stable until 2020 when it reached a 10-year maximum of nearly 530,000 ha.

Between 2000 and 2021, the annual area burned was highly variable. The two years with the greatest area burned were 2014 and 2021, with over 4.5 million ha and 4.3 million ha, respectively. The year with the lowest area burned was 2020, with only about 220,000 ha burned.

Between 2000 and 2021, the number of forest fires was variable, ranging between the 10-year high of 9,800 fires in 2006 to a 10-year low of about 4,000 fires in 2020. In 2021, there were about 6,600 fires.

The net carbon emissions in Canada’s managed forest were 165 million tonnes of carbon dioxide equivalent (Mt CO²e) in 2019, taking into account both human activities and natural disturbances. The trend in net carbon emissions from 1990 to 2020 is toward larger annual emissions, but with high annual variability. Canada’s managed forests were a net sink of carbon, absorbing carbon from the atmosphere, from 1990 to 2001, with the exception of 1995 and 1998, when managed forests emitted carbon. From 2002 to 2020, taking into account both human and natural disturbances, Canada’s managed forests emitted carbon each year. The two highest emitting years were 2017 (about 230 Mt CO²e) and 2018 (about 260 Mt CO²e), and the lowest emitting year was 2020 (just over 5 Mt CO₂e).

The graph also shows the annual area disturbed (in hectares) within Canada’s managed forest for each year from 1990 to 2020, with on average the area disturbed by insects making up the largest share of the area disturbed, followed by area of forestry activities, then by area burned, and last by area of firewood harvest. The total area disturbed varies between 2 and 16 million ha per year, with larger areas disturbed from 2001 to 2006, and smallest areas disturbed from 1990 to 2000 and from 2009 to 2013.

Areas subject to human activities in Canada were a net sink of GHGs from 1990 to 2003. However, the size of the sink had been decreasing slowly from a sink of 70 Mt CO²e in 1990 to about 20 Mt CO²e in 2003. By 2005, these areas became a source of nearly 15 Mt CO²e, but then returned to a sink of nearly 18 Mt CO²e by 2009. Since 2010, areas subject to human activities have been both a source and sink of GHGs, but remain within a narrow range. In the last 10 years, the highest source occurred in 2019 with about 7 Mt CO²e, and the largest sink occurred in 2012 with nearly 5 Mt CO²e.

The graph also shows the annual area disturbed (in hectares) within Canada’s managed forest for each year from 1990 to 2020, with on average the area disturbed by low mortality insects making up the largest share of the area disturbed, followed by area of forestry activities, and last by area of firewood harvest. The total area disturbed varies between 3 and 13 million ha per year, with larger areas disturbed from 2003 (nearly 9 million ha per year) and 2020 (nearly 13 million ha). The total area disturbed follows a generally increasing trend until 2003, after which it decreases until around 2013, then increases again until 2020.

Since 1990, net annual GHG emissions that are due to natural disturbances in Canada’s managed forests have been closely related to the annual area burned. As the amount of forest burned by wildfires varies widely from year to year, the trend in carbon emissions also varies, with large up and down swings over the span of a year or two. The lowest emissions were in 1992, with a net removal of carbon of nearly 50 Mt CO₂e, while the highest emissions were in 2015, with a net emission of about 260 Mt CO₂e. However, the graph shows an overall trend toward increasing carbon emissions caused by natural disturbances over time, until a sudden drop in 2020 to around 10 Mt CO₂e.

The graph also shows the annual area disturbed by high mortality insects and wildfires within Canada’s managed forests from 1990 to 2020. The area disturbed by both causes is highly variable from year to year, with the area disturbed by high mortality insects making up the larger share overall. The total area disturbed is generally lowest from 1990 to 2000, then increases on average over the period of 2001 to 2008, then decreasing to mid-range values between 2009 and 2020. The total area disturbed by high mortality insects and wildfires peaked at about 7 million ha in 2006/2007, and were at their 20-year lows before 1998 at below 1 million ha.