In the depths of the Lac-à-la-Tortue bog
Northern pitcher plant, Lac-à-la-Tortue bog (Photo by Martin Beaulieu)
Peatlands are wetlands composed of plant residues accumulated over the centuries. Although they are widespread in the Quebec landscape, they remain unknown to a large part of the population. Yet they provide us with many essential ecological services, such as water filtration, flood control. They are also valuable allies in the fight against climate change through their role in carbon capture.
As part of a research project entitled “Multiproxy analysis of inception and development of the Lac‐à‐la‐Tortue peatland complex, St Lawrence Lowlands, eastern Canada,” my objective was to reconstruct the conditions that led to the development of the largest peat complex in the St. Lawrence Lowlands — Lac-à‐la‐Tortue — and improve our understanding of its origins. This complex is located near the municipalities of Shawinigan, Notre-Dame-du-Mont-Carmel, Saint-Narcisse and Saint-Maurice.
Evidence of the past
Peat bogs are excellent ecological and climatic archives. Due to their wet, acidic conditions, there is significant accumulation of peat, and traces of plants, micro-organisms and pollen grains have been preserved for several thousand years. Detailed study of these fossils allows us to reconstruct the type of vegetation or climate that existed in the past.
The ability of peat bogs to store carbon in the form of peat and prevent its release into the atmosphere illustrates their essential role in the fight to reduce industrial pollution and greenhouse gas emissions. Peat bogs contain more than a third of the planet's terrestrial carbon stock, which is a considerable amount! A better understanding of the climatic and environmental conditions that affect the development of peatlands is essential to predicting how they will respond to current and future climate change. This is especially important if we want to preserve the essential ecological services they provide us.
In the belly of the bog
Just getting around the Lac-à-Tortue bog was an adventure! For two consecutive summers, my team and I traversed the 66 km2 site on foot. Most of the time, rain boots proved useless, as the water reached our knees. We battled voracious flies and intense heat while carrying a “carottier” that weighed several kilos. This carottier was used to collect our precious “carrots” — the peat samples that would allow us to learn more about the history of the vegetation.
What the peat reveals
We then brought our samples to the laboratory for analysis. This meticulous, but exciting, work can take up to two years. From the remains of leaves, stems or plant seeds preserved in the peat, we precisely identified the plants that were present at the time the peat bog was formed.
We were also able to determine from the analysis of a core from the deepest part of the bog that it originated from a wet depression about 10,350 years ago, just after the Champlain Sea withdrew from the region, making it the oldest peat bog in the St. Lawrence Lowlands of Quebec. We estimated its carbon stock at about 4.73 million tonnes.
To our knowledge, this study was the first to provide an estimate of the total carbon stock contained at the scale of an entire peat bog for Quebec. The study highlights the important value of wild peatlands as carbon sinks — particularly in densely populated areas where very few intact peat ecosystems remain, as most have been used for horticultural or agricultural purposes.
Learn more here.
By Louis-Martin Pilote, holder of a master’s degree in geography and a research professional at the laboratoire de paléoécologie continentale de la Chaire Déclique (Geotop-UQAM).
Passionate about biogeography, Louis-Martin devotes himself above all to the study of northern peatlands, the history of their development in association with the landscape, their role in the global climate system and their surprisingly diverse and colourful flora.