Logged forests, cultivated fields, drained wetlands: Quebec’s lands are a net emitter of carbon. For the first time, this sector is included in the province’s greenhouse gas (GHG) emissions inventory, published last week.
In 2022, so-called “managed” lands in Quebec released the equivalent of 12 million tonnes of CO2. The new report shows that our way of exploiting the territory, starting with its forests, exerts a serious influence on the climate, equal to 15% of our direct emissions.
In the jargon, this sector is called land use, land use change and forestry (LULUCF). We count the exchanges of GHGs between “managed” lands and the atmosphere. All these exchanges are not harmful: land can emit carbon, but also absorb it.
Managed lands are those that undergo human interventions for productive, ecological or social purposes. We are talking about forests exploited for their wood, but also cultivated lands and disturbed wetlands — in particular, peat bogs drained for their peat and hydroelectric reservoirs.
The LULUCF sector includes the GHG flows associated with these lands, but also those associated with the destruction of natural environments for the construction of “establishments”: cities, roads, mines, etc. Added to this are emissions from “harvested wood products”, such as wood, cardboard and paper, which are closely linked to forests.
Result: in Quebec, the cumulative emissions exceed those of absorptions. “By looking at these data, we understand that the forest is not saving us, and that we cannot sit on our laurels,” observes Évelyne Thiffault, a professor at Laval University specializing in forest carbon.
In Quebec’s LULUCF report, the forest largely leads the way. Every year for 25 years, trees absorb at least 10 million tonnes of CO2 while pushing. At the same time, wood products release at least 20 million tonnes into the atmosphere.
These rejections are not instantaneous. “Paper has a much shorter lifespan than wood used in furniture or a house,” explains Dominique Blain, retired director of the division of Environment and Climate Change Canada (ECCC) dedicated to GHG inventories, and specialist of land carbon.
The authors of the analysis therefore consider the typical lifespan of wood products to estimate their emissions. Thus, a wooden piece of furniture manufactured in 1980 could see its carbon become an emission in the 2030 balance sheet, when it will be transformed into a kindling stick.
Opposing trends
According to the Quebec inventory, between 1999 and 2009, net emissions from land fell rapidly, going from 25.0 to 1.4 million tonnes of CO2 per year. This trend is mainly the result of increased carbon absorption by forest lands during the period.
In fact, during this decade — marked by a crisis in Quebec forestry and concluded by an economic crisis — logging fell by half, notes the Quebec Ministry of the Environment in its inventory. The trees therefore had the opportunity to siphon more atmospheric carbon.
In the following decade (2010-2019), forest harvesting resumed, and net carbon emissions began to rise again. According to the ministry, the increase in recent years is largely explained by the ravages of the spruce budworm which, by killing trees, annihilates their capacity to swallow carbon.
The data presented by the Government of Quebec are taken from an ECCC analysis which, for the first time in 2024, details the results of the land sector at the provincial level. Note that land emissions do not appear in the main balance sheet of Quebec’s GHG emissions, which is the subject of a reduction target set by law (37.5% below 1990 emissions, in 2030) nor in that of Canada.
Xavier Cavard, specialist in forest carbon at the University of Quebec in Abitibi-Témiscamingue, also recalls that the federal calculation excludes forest fires from emissions from the LULUCF sector.
“Society has little control over forest fires,” he explains. The experts therefore agreed that it was better to measure their emissions separately from LULUCF’s assessment, which is based — by definition — on the repercussions of human interventions. That said, emissions from forest fires are very significant compared to other terrestrial carbon flows. During the record season of 2023, in Quebec, they released more than 180 million tonnes of CO2more than double the province’s annual anthropogenic emissions.
Aim for neutrality
What should we make of the LULUCF sector’s assessment? Mme Thiffault thinks that Quebec should give itself an official target to reduce net emissions from its lands to zero. To achieve this, she recommends, before trying to increase the sequestration carried out by trees, to focus on our way of using wood products.
Concretely, we should increase the fraction of long-lasting products (houses, furniture) and reduce that of short-lived products (pulp and paper). “With a small change, we could improve our balance sheet quickly. It’s a big lever that we haven’t yet used enough,” thinks the professor.
Improving forestry practices — such as avoiding stirring the soil with machinery, or planting more carbon-efficient species after cutting — will also limit carbon leaks, but at a slower pace.
Efforts must also affect other types of land. We are already seeing dairy producers testing perennial crops to enrich their soil with carbon. Among scientists, a new research program is starting in southern Quebec to measure GHG fluxes from wetlands. In recent years, these questions have attracted increasing interest.
Dominique Blain, who participated for a long time within the Intergovernmental Panel on Climate Change (IPCC) to develop the methodology for accounting for LULUCF emissions, thinks that land emissions have not always had the attention they deserve.
“In Canada, this is a very important issue, because our territory is immense,” she says. Decision-makers, in general, are poorly informed. They are often under the impression that our forest lands offset all our fossil emissions, but that is a shortcut. » Conversely, she emphasizes, our land use accentuates warming.
