The boreal forest as a carbon "bank account"

More than 186 gigatonnes (billion tonnes) of carbon are stored in the Canadian boreal forest, making it the largest terrestrial carbon “bank account” on the planet. This huge quantity is equivalent, in terms of GHG emissions, to 27 years worth of global consumption of fossil fuels. Thus, the boreal forest acts as an enormous carbon warehouse, storing between 200 and 1000 tonnes of carbon per hectare.

Contrary to what might be expected, 80% of the carbon stored in the boreal forest is contained in its soils, not in its above-ground vegetation. Indeed, although trees and plants absorb atmospheric carbon through photosynthesis, only 20% of this carbon is stored in the vegetation itself. The remainder is accumulated in the boreal forest’s porous soil, where organic matter decomposes slowly because the activity of bacteria and fungi is slowed by a combination of cool temperatures and abundant water.

This slow decomposition process is responsible for the very large quantities of carbon stored in the soil. By contrast, carbon in tropical forests is mainly stored in above-ground vegetation, since high temperatures promote the rapid decomposition of organic matter in the soil.

Overall, the boreal forest can store up to twice the carbon per hectare as a tropical forest, and nearly four times that of a temperate forest.