Net Carbon Effect of Canadian Forest Ecosystems

Prior to the escalation of wildfire activity in the early 2000s, Canada's managed forests functioned as a significant carbon sink. Research published by Environment and Climate Change Canada scientists (Curasi et al., 2025) demonstrates that Canadian terrestrial ecosystems have been a net carbon sink since the mid-twentieth century, primarily due to forest recovery from widespread wildfire and timber harvest that occurred before 1940. Between 2015 and 2020, Canadian ecosystems absorbed an estimated 366 ± 88.6 teragrams of carbon per year (TgC/yr), according to a study published in Nature by Byrne et al. (2024). Natural Resources Canada's managed forest carbon statistics confirm that in years with low natural disturbance — such as 2000 and 2001 — the forests acted as a net sink, absorbing 34.7 and 21.9 Mt CO₂e respectively. The carbon balance, however, has always been highly variable. Human activities in managed forests (harvesting, site preparation, regeneration) have consistently contributed a net source of 20 to 38 Mt CO₂e per year over the five years prior to 2023. Natural disturbances — primarily wildfire and insect outbreaks — have ranged from as low as 3 Mt CO₂e to as high as 294 Mt CO₂e per year in the same period, demonstrating the extreme volatility of the system.

The 2023 Canadian wildfire season was the most destructive in recorded history. According to Natural Resources Canada, 7.9 million hectares of managed forest burned — more than the sum of the four highest previous wildfire years combined. The peer-reviewed study by Byrne et al. published in Nature (2024) estimated that 15 million hectares burned in total across Canada, approximately seven times the average burned area over the preceding 40 years (1983–2022 mean: 2.2 million hectares). Fire carbon emissions reached 647 TgC (range: 570–727 TgC) according to top-down atmospheric inversion estimates. This figure is approximately four times Canada's annual fossil fuel emissions (149 TgC/yr) and comparable to India's entire annual fossil fuel output (740 TgC/yr). The Copernicus Atmosphere Monitoring Service confirmed that Canada produced 23% of all global wildfire carbon emissions in 2023 — the highest share ever recorded for the country. Natural Resources Canada's 2025 report quantified the total net greenhouse gas flux at 1,138 Mt CO₂e, of which 1,070 Mt CO₂e came directly from wildland fires. The previous record for wildland fire emissions from managed forests was 292 Mt CO₂e in 2021 — meaning the 2023 figure was 3.7 times the prior record.

The 2023 fire emissions were not distributed evenly across Canada. Byrne et al. (2024) identified two dominant emission clusters with sharply different ecological and climatic profiles. Northwestern Canada, centred on the Great Slave Lake region of the Northwest Territories (approximately 57–62°N, 110–125°W), contributed roughly 61% of total fire carbon emissions. This region experienced a precipitation deficit of 8.1 cm (27% below average) and exceptionally warm temperatures (+2.6°C above the May–September mean). The drier boreal landscape in this area — dominated by black spruce and jack pine — is particularly fire-prone under drought conditions. Western Quebec (approximately 49–55°N, 72–80°W) contributed roughly 15% of total fire emissions. This region is typically wet, but experienced exceptional drought in 2023, with precipitation 23.7 cm (49%) below average, combined with extreme heat and vapour pressure deficit during June and July. The remaining emissions were distributed across Alberta, British Columbia, Ontario, and other provinces. Historically, Alberta and Ontario have been the highest-emitting provinces in terms of forest carbon, accounting for approximately 38% and 23% of the national total respectively. The boreal forest, which constitutes more than 75% of Canada's total forest area, dominates the national carbon balance and is the ecosystem most vulnerable to climate-driven fire intensification.

The 2023 season was not an isolated event but rather the most extreme expression of a longer-term structural shift. Natural Resources Canada has noted that "recent high emissions from wildland fires in the managed forests are no longer offset by forest regrowth from previous wildland fires, resulting in net emissions into the atmosphere." Research by Curasi et al. (2025) — authored by scientists from Environment and Climate Change Canada, Natural Resources Canada, Carleton University, the University of Toronto, and the University of British Columbia — provides the first physically coherent wall-to-wall estimates of all major carbon pools and fluxes for Canada. Their analysis concludes that since the early 2000s, wildfire disturbance has been driving Canadian forests towards becoming a carbon source, and that continued increases in wildfire activity will further weaken, and may ultimately reverse, Canada's role as a carbon sink. Climate projections reinforce this concern. Byrne et al. (2024) note that under CMIP6 climate models and the SSP 2-4.5 scenario, the temperatures experienced in 2023 will be typical by the 2050s. If fire seasons of 2023 magnitude (approximately 4% of forest area burned per year) become the norm, all of Canada's forests could theoretically burn within a 25-year cycle — a rate far exceeding the capacity of boreal ecosystems to regenerate and recapture carbon.

As of early 2026, Canada's managed forests remain in a state of heightened vulnerability. The carbon debt accumulated from the 2023 fire season will take decades to recover through natural regrowth, even under favourable conditions. The 2024 and 2025 fire seasons, while less extreme than 2023, continued the pattern of above-average burned area in several provinces. Canada's approach to forest carbon accounting distinguishes between emissions under the influence of human activities (harvesting, regeneration, fire suppression) and those associated with natural disturbances beyond human control. In 2023, human activities accounted for approximately 20.2 Mt CO₂e, while natural disturbances accounted for 1,118 Mt CO₂e — illustrating that the overwhelming driver of the carbon balance shift is wildfire, not forestry operations. The policy implications are significant. Forest carbon management strategies that rely on assumptions of stable sink capacity are no longer tenable. Adaptation measures — including enhanced fire prediction, fuel management, and strategic reforestation with fire-resistant species — will be essential to mitigate future carbon losses. However, the fundamental driver is climate change: warmer temperatures, longer fire seasons, and more frequent drought conditions are creating a feedback loop in which fire releases carbon, which accelerates warming, which increases fire risk.