By Ken Gregory P.Eng.                                                                          July 17, 2023

A recent paper provided estimates of carbon sinks in North America. The authors used an ensemble of 19 state-of-the-art dynamic global vegetation models to improve carbon sink estimates and study the drivers of its variability. Carbon sinks refers to the net absorption by the land of carbon dioxide (CO₂).  The study reports that the carbon sink of North America increased from 1,140 megatonnes (Mt)CO₂/yr during 2000-2009 to 1,610 MtCO₂/yr during 2010-2019. Vegetation absorbed 57% of the CO₂ causing a greening of the continent and 30% was absorbed by the soil and 13% by litter.

In Canada, the carbon sink increased from 550 MtCO₂/yr during 2000-2009 to 730 MtCO₂/yr during 2010-2019. These values are net of emissions by land use changes. During the same period, Canada’s average annual emissions of greenhouse gases (GHG) were 724 MtCO₂eq and 716 MtCO₂eq while emissions of CO₂ were 571 MTCO₂ during both periods. The GHG emissions include CO₂, methane, nitrous oxide and four other minor greenhouse gases. GHG emissions are reported in carbon dioxide equivalents (CO₂eq) using global warming potential factors. The table below shows the CO₂ and GHG emissions, CO₂ sinks and the net emissions.

The calculations show that Canada’s emissions have been declining despite our rapidly increasing population while the absorption of CO₂ into land sinks have increase by 33% between the two decades. Canada’s boreal and temperate forests account for 88% of its land sinks. The increasing absorption of CO₂ is causing an increase of Canada’s gross primary productivity suggesting a strong CO₂ fertilization effect on photosynthesis.  During the 2010-2019 decade, Canada’s net CO₂ emissions were -159 MtCO₂ and the net GHG net emissions were -14 MTCO₂eq. The author wrote that across Canada “we found a persistent and positive effect of climate across both decades” due to increasing temperatures. While there is large uncertainty in the CO₂ sink estimates, Canada has likely already surpassed net zero GHG emissions.

Why is Canada not accounting for the net CO₂ sinks of our forests? Why are we planning to spend over $130 billion per year to reach net zero when we are already below net zero emissions including our land CO₂ sinks?

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This article first appeared in the June 2023 FoSS Membership Quarterly Newsletter No. 78.