RESOLVING THE LEDGER
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edited by Swati Mestri , reviewed by Robert Egan
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Add as preferred source Lakes play an important role in capturing and storing carbon, which accumulates in their sediments. But the amounts they can absorb have varied considerably over time. Jean-François Lapierre, a professor in the Department of Biological Sciences at Université de Montréal, is part of a research team sorting out natural variations from human-influenced changes.
Working with Hydro-Québec, the team set out to assess the impact of hydroelectric reservoirs on the carbon cycle compared with natural variations. Partial results have been published in the journal Environmental Research Letters .
"Many studies have focused on the long term or the industrial era, but we wanted to compare the evolution of accumulation rates in lake sediments over the past 11,000 years with trends over the last 150 years," explained Aude Flamand, a member of the research team.
To do so, the researchers relied on existing data. "We had neither the time nor the funds to collect new data in the field, but there is a wealth of data already available that we were able to use," Flamand said.
The existing data were incomplete, as they mostly came from studies that weren't focused on carbon accumulation, but they often contained at least two of the three variables—sediment density, percentage carbon content and dating—needed to calculate carbon accumulation. The team therefore developed a predictive model that links sediment density to organic matter content and is specifically adapted to the wide variety of boreal and temperate lake sediments.
"The existing models were not suited to boreal lakes, which generally contain very high levels of organic matter," Flamand said.
The disparate data sources presented numerous challenges. For one thing, the dating methods varied—radiocarbon for the oldest samples and lead-210 for the more recent ones.
"Two dating methods are rarely used on the same core," Lapierre explained. "It makes it difficult to compare accumulation rates across centuries and millennia."
While there have been significant climatic disruptions at various points during the Holocene, the most pronounced changes in accumulation rates occurred in recent centuries. "It seems that the arrival of the first settlers already disrupted accumulation rates, but starting in 1850, with the beginnings of industrialization, the variations intensified," Lapierre said.
In some lakes, sporadic decreases in carbon accumulation rates were found. "We expected an increase in accumulation rates, and not necessarily an increase in variability," Lapierre said.
"This means the lakes are becoming more sensitive to disturbances," Flamand added.
Ecosystems naturally sequester carbon, but the rate at which they do so depends on various factors: climate, nutrient inputs and the amount of carbon supplied by the watershed.
"The key takeaway from our study is that since industrialization, this function of aquatic ecosystems has been pushed far outside its natural range, for a variety of reasons linked to human activity," Lapierre explained.
The researchers now want to identify the factors driving this trend so they can make projections and scenarios for the future, based on variables such as projected climate change or changes in land use. After analyzing the sediment data, they plan to focus on measurements of the water column over time.
This study therefore sheds new light on the impacts of human activity on the natural carbon cycle. "It's important to quantify our carbon footprint, but also to compare it with the range of historical natural variations, which represent the true baseline," Lapierre concluded.
Aude Flamand et al, From Holocene stability to industrial acceleration: shifting patterns of carbon accumulation in North American boreal and temperate lakes, Environmental Research Letters (2026). DOI: 10.1088/1748-9326/ae5a4c
Journal information: Environmental Research Letters
Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile →
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