This text is part of the special Environment section
Forests play a significant role in the fight against climate change, but they are also affected by it. Two recent studies conducted in Quebec help to better understand these dynamics.
Trees absorb CO throughout their life.2present in the atmosphere. They then separate the carbon from the oxygen, retaining the former in their roots, trunk and branches and releasing the latter into the atmosphere. However, the CO2 accounts for three-quarters of annual greenhouse gas (GHG) emissions. Planting trees and preserving forests are thus generally perceived as means of combating CO emissions.2and therefore against climate change.
But what impact do these natural carbon sinks really have? Researcher Damon Matthews, a professor in the Department of Geography, Urban Planning and Environment at Concordia University, has looked into this question. “Natural carbon storage has the particularity of being usually temporary, since deforestation and forest fires eventually release carbon into the atmosphere,” he points out. We therefore wanted to assess the long-term impact of these natural structures on global warming, taking this aspect into account. »
Not a quick fix
His team made projections based on different scenarios of CO emissions2 assuming that natural sinks would hold carbon until 2050 before releasing it. The results show that if CO emissions2 continue to rise, even moderately, over the next few decades before they begin to decline, temporary carbon storage will only be able to delay the inevitable rise in average temperatures by a few years to 3 degrees or more at the end of the century.
On the other hand, if countries rapidly reduce their emissions and manage to achieve carbon neutrality by 2050, as foreseen by the Paris Agreement signed in 2015 at COP21, natural carbon removal structures will become more effective. They would then contribute to a drop in peak temperatures, which would help achieve the Paris Agreement’s goal of limiting the rise to below 2 degrees.
“Research demonstrates that natural carbon capture can play a positive role in combating climate change, but it cannot in any way replace a drastic reduction in CO2 emissions.2 “, notes Damon Matthews.
The recent Intergovernmental Panel on Climate Change (IPCC) report recognizes that even if we drastically reduce our GHG emissions, we will need to implement carbon dioxide removal techniques, including natural carbon capture. CO2to get us to carbon neutrality.
grow in the sun
Forests themselves are also already affected by climate change. Emmanuel Amoah Boakye, a doctoral student from the University of Quebec in Abitibi-Témiscamingue, took a close interest in the impact of climate variations on the mixed boreal forest, which represents a transition zone between the temperate forest of southeastern Canada and the northern boreal forest.
He analyzed growth data for two varieties of trees, jack pine and trembling aspen, spanning almost two centuries. This allowed him to see that the trembling aspen grew faster due to the warming of the average temperature, whereas the growth of the jack pine, a tree more accustomed to low temperatures, did not suffer too much, but did not don’t take advantage of it either.
“Research has shown that the effect of climatic variations differs from one tree species to another, but above all that growth is greatly influenced by the local conditions in which the trees grow, such as humidity, degree competition with other trees or disturbance factors, such as the presence of insect pests”, emphasizes the researcher.
Vulnerable species
Emmanuel Amoah Boakye recently published an article on the impact of insect pests on tree growth in the scientific journal Ecology and Evolution. In it, he reveals the results of research on more than 2,000 trees of 5 different species present in the boreal mixed forests of western Quebec. These show that the growth rate of the two tree species that serve as hosts for the spruce budworm decreased between 1967 and 1991, while it increased for the other three non-host species.
“Thus, if climate change favors insect epidemics or the arrival of new species of insect pests, this could greatly reduce the generally positive impact of rising temperatures on tree growth,” warns the researcher.