An increase in wildfires, drought, and insect infestations could destroy large portions of Canada’s vast boreal forests by the end of this century, according to a peer-reviewed Canadian Forestry Service study published last week in the journal Ecological Applications.
“We have a problem in big parts of Canada, when you see 100% of the volume (of trees), in the worst-case scenario, will probably die,” forest ecology biologist Dominique Boucher, one of the seven study authors, told National Observer.
“The conditions that are driving those kinds of big fires…will be much more prevalent in the future, and they will occur much more often,” said forest ecology research scientist and study co-author Yan Boulanger.
The worst-case scenario, in which fossil fuel use continues unabated and average global warming reaches 4.8°C by 2100, is beginning to recede as a top-line concern for some scientists, based on the still-incremental goals in the Paris agreement and the pace of the off-fossil transition. But the study still provides one view of the impact of climate change on the four most serious natural disturbances now facing the boreal: wildfires, drought, spruce budworm outbreaks in the east, and mountain pine beetle in the west.
“When disturbance effects are cumulated, important changes in volumes at risk are projected to occur as early as 2011-2041, particularly in central and eastern Canada,” the paper states. “In our last simulation period covering 2071 to 2100, nearly all timber volumes in most of Canada’s forest regions could be at risk of being affected by at least one of the four natural disturbances considered in our analysis, a six-fold increase relative to the baseline period (1981-2010).”
“If those natural disturbances are increasing in future, there will be a great impact on the trees themselves, on the mortality potential,” Boulanger added. “Timber volume will be much more at risk to mortality in the future, in some specific areas. Some places will be more affected by fire, other places will be more affected by certain insect outbreaks.”
Which means that “effectively managing Canada’s boreal forest is crucial for the planet, as the country holds almost a third of Earth’s boreal zone,” the Observer notes. “The forests and the earth under them also support jobs and communities, provide food and resources, and are home to 70% of Indigenous communities.”
The levels of forest loss envisioned by the study also have implications for forest regulations and annual allowable cuts. “By 2100, estimated wood volumes not considered to be at risk could be lower than current annual timber harvests in central and eastern Canada,” the paper warns. “Current level of harvesting could thus be difficult to maintain without the implementation of adaptation measures to cope with these disturbances.”
According to Werner Kurz, senior research scientist at the Canadian Forest Service and head of its carbon accounting team, every hectare of forest land consumed in a fire like the one in Fort McMurray in 2015, released about 170 tons of carbon-dioxide-equivalent (CO2 eq) into the atmosphere.
(source: http://www.washingtonpost.com/news/energy-environment/wp/2016/05/20/the-…-fires-stunning-pulse-of-carbon-to-the-atmosphere)
Emissions include carbon dioxide but also methane and nitrous oxide. Methane (CH4) has a Global Warming Potential (GWP) of 28-36 over a 100 year period, but a GWP of 84-87 over a 20 year period which is the average time CH4 last in to the atmosphere. Nitrous oxide, which has a average life span of 100 year into the atmosphere, has a GWP of 265-298.
(source: http://www.epa.gov/ghgemissions/understanding-global-warming-potentials)
It is estimated that the 2015 Fort McMurray fire itself released approximately 85 million tons (Mt) CO2 eq into the atmosphere. A total of 3.9 million hectares of Canada’s forests burned in 2015, potentially sending around 663 Mt CO2 eq into the atmosphere (total GHG emissions for Canada in 2015 were 722 Mt). Emissions from forest fires are not accounted in Canada’s annual report on GHG emissions.
An average of 9,000 fires burn more than 2 million hectares each year in Canada. This is twice the average area burned in the early 1970s, and various modelling scenarios predict another doubling or more by the end of this century, because of warmer temperatures expected as a result of climate change. The growth in fire activity will have major implications for forest ecosystems, forestry activities, community protection and carbon budgets.
What is specially concerning to scientists is the impact of forest fires on peatland ecosystems. Peat fires release significant amounts of CO2 and other GHG. Peat fires also release mercury into the atmosphere at a rate 15 times greater than upland forests.
(source: Natural Resources Canada, Dec. 04, 2013: “Peatland fires and carbon emissions”)
The combined Boreal and Subarctic regions contain 97% (142.94 Gt) of the soil organic carbon mass occurring in Canadian peatlands. The peatland sensitivity model indicates that approximately 52% (74.16 Gt) of the organic carbon in these two regions will be severely to extremely severely affected by climate change.
(source: Canadian Water Resources Journal, Charles Tarnocai, Agriculture & Agri-food Canada, May 2009)