Historically, lakes have been perceived as contributors to carbon dioxide emissions; however, recent research indicates they may function as carbon sinks. Research conducted by Uppsala University indicates that lake shorelines sequester more carbon than previously estimated, underscoring the necessity of including these littoral zones in assessments of the continental carbon balance.

The littoral zones of lakes are typically bordered by aquatic plants, which are among the fastest-growing flora globally. They absorb significant quantities of carbon from the atmosphere, while substantial amounts of carbon from residual plant material are sequestered in the sediments. The overall littoral zone of lakes globally is four times longer than ocean coastlines; nonetheless, the significance of lake shorelines has previously been overlooked in global carbon budgets, until now.

A recent article from Uppsala University is the inaugural study to incorporate littoral zone vegetation into lake carbon budgets, demonstrating that lakes may function as carbon sinks rather than emitting carbon into the atmosphere.

“We were planning to write a conceptual paper about how aquatic plants in the littoral zone are overlooked in lake carbon cycling. But after doing some initial calculations quantifying the role of these plants, we quickly realised that littoral zones could be a significant player in the global carbon budget! So, our conceptual paper eventually turned into the first global carbon budget to include the critical contribution of aquatic plants from lake littoral zones,” stated Charlotte Grasset, first author of the study and researcher at Uppsala University.

Lake transitions from being a net carbon source to a net carbon sink

The authors conducted the inaugural global-scale estimate of littoral zones’ contribution to the carbon budget of lakes by utilising existing data and a straightforward model linking littoral zones to the lake core.

“We find that adding the littoral zone vegetation to the global carbon budget of lakes substantially changes the carbon accounting of lakes. Depending on the values used, we found that when littoral zones were included, lakes switched from a net carbon source to a net carbon sink; that is, the carbon stored annually in lake sediments was greater than the carbon released to the atmosphere,” stated Grasset.

Rehabilitating lakeshores for climate and biodiversity enhancement

The writers unanimously emphasise that considerable work remains to be accomplished. Despite their estimations being grounded in the most reliable data now accessible, additional measurements are necessary to enhance these preliminary conclusions regarding lakes. This encompasses an enhanced comprehension of the spatial distribution of vegetated littoral zones in lakes, together with more precise assessments of carbon gas exchange among aquatic plants, sediments, the atmosphere, and the lake’s centre.

“We hope this study will stimulate future research on the critical role of lake littoral zones in carbon budgets, and of the possible role of restoring the lake littoral as a nature-based solution,” said Grasset.

The authors contend that, after over 15 years of recognising ‘blue carbon’ plants in marine coastal habitats as a nature-based solution, it is now imperative to direct attention towards lake littoral zones to enhance carbon accounting, improve water quality, and restore aquatic biodiversity.

Summary

• New research shows lake shorelines (littoral zones) can act as carbon sinks, not just sources.
• Aquatic plants in littoral zones grow rapidly, absorb carbon, and store it in sediments.
• Global lake shorelines are four times longer than ocean coastlines, yet are often overlooked in carbon budgets.
• Including littoral zones in carbon accounting can shift lakes from net carbon sources to net carbon sinks.
• Restoring vegetated lake shores could boost climate action, water quality, and biodiversity.

Original Publication
Authors: Charlotte Grasset, Jorrit P. Mesman, Lars J. Tranvik, Roxane Maranger and Sebastian Sobek.
Journal: Nature Geoscience
DOI: 10.1038/s41561-025-01739-8
Article Title: Contribution of lake littoral zones to the continental carbon budget
Article Publication Date: 4-Aug-2025

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