The Tollund Man was c. 30-40 years old when he died by hanging c. 405-380 BCE. He was
found in 1950 in a bog c. 10 km west of Silkeborg. The Tollund Man’s head was preserved
but his body dried out; now a recreation of the body is on display.
Peat bogs, mostly made up of a moss called Sphagnum, are special environments that play a key role in regulating the Earth’s climate by storing large amounts of carbon. These bogs are also famous for preserving ancient human remains, known as bog bodies, due to their cold, acidic, and oxygen-poor conditions. Yet, scientists have long been puzzled by two strange patterns in these ecosystems: the unusually high amount of carbon dioxide compared to methane being released and the very slow breakdown of dead plant material. Interestingly, both of these puzzling features actually help slow down climate change by either trapping carbon or reducing the release of more potent greenhouse gases. Solving these mysteries is important because peatlands hold nearly a third of all the carbon found in soil on Earth—on par with the total carbon currently present in the atmosphere.
A group of researchers, including Alexandra B. Cory, Rachel M. Wilson, M. Elizabeth Holmes, William J. Riley, Yueh-Fen Li, Malak M. Tfaily, Sarah C. Bagby, Patrick M. Crill, Jessica G. Ernakovich, Virginia I. Rich, and Jeffrey P. Chanton from a number of universities and laboratories across the United States and Europe, set out to better understand this. Their findings, which were published in the respected journal Scientific Reports, suggest that a chemical process known as the Maillard reaction, a type of non-living chemical interaction between sugars and proteins, most famously known for creating the browned, flavorful crust on roasted or grilled foods like toast and seared meat, could help explain both puzzles. This reaction usually happens when certain sugars and proteins interact and, unlike enzyme-driven browning processes that depend on microbes, this particular reaction can occur without any involvement of living organisms.
Their results show that natural chemical reactions, not involving living organisms, inside the peat can produce significant amounts of carbon dioxide. To test this, the scientists carried out experiments using both natural peat and lab-made mixtures. Even peat that had been sterilized—meaning all living microbes were removed—still released carbon dioxide, showing that this gas can be produced by chemical reactions alone. These reactions also created complex nitrogen-rich compounds, which likely made it harder for microbes to access the nitrogen they need. Nitrogen is an essential nutrient that microbes rely on to carry out decomposition, and reduces competition with Spagnum moss in the bog because it is adapted to low Nitrogen environments.”
With less nitrogen available, the microbes in the peat become less active, slowing down how quickly they can break down plant material. At the same time, the chemical reactions increased the amount of carbon dioxide released without producing a similar amount of methane, which goes against the usual models that expect both gases to be released in equal amounts. This uncoupling, or separation, of gas production from microbial processes gives scientists a fresh way to think about how these environments work.
“Our results suggest that non-biological Maillard reactions, driven by compounds from Sphagnum moss like galacturonic acid—a kind of natural sugar acid found in plant cell walls—significantly influence carbon cycling in peat bogs,” said Dr. Cory, the study’s lead researcher. “These reactions not only produce carbon dioxide on their own, but they also trap nitrogen in forms that microbes can’t use, which slows down decomposition.”
The researchers confirmed that galacturonic acid, which is found in large amounts in Sphagnum moss, can react with common proteins even at the low temperatures found in bogs. These reactions were seen both in lab-made mixtures and in natural peat samples, and the chemical evidence lined up with the steps known from earlier studies of the Maillard reaction.
Looking at the broader impact, Professor Chanton added, “This non-biological process changes how we think about carbon in peatlands. Most climate models—tools used by scientists to simulate and predict future climate behavior—focus only on microbial activity. If we also consider carbon dioxide from these chemical reactions, we can improve our predictions about greenhouse gas emissions from wetlands.”
Including these insights in global climate models is especially important because Maillard reactions tend to speed up as temperatures rise. As the planet continues to warm, these reactions could lead to even more carbon being released from peat bogs. This study challenges long-held beliefs about how carbon behaves in wetlands and encourages further research into how chemistry, not just biology, shapes these ecosystems.
Journal Reference
Cory A.B., Wilson R.M., Holmes M.E., Riley W.J., Li Y.F., Tfaily M.M., Bagby S.C., Crill P.M., Ernakovich J.G., Rich V.I., Chanton J.P. “A climatically significant abiotic mechanism driving carbon loss and nitrogen limitation in peat bogs.” Scientific Reports, 2025; 15:2560. DOI: https://doi.org/10.1038/s41598-025-85928-w
Image Credit
Original image by Silkeborg Museum. Uploaded by Ibolya Horváth, published on 12 June 2024. Creative Commons Attribution
About the Authors
Alexandra Cory received her PhD in 2022 from Florida State University, where she studied the biogeochemical mechanisms that allow peat bogs to act as climate mitigators—by retaining organic carbon exceptionally well and emitting comparatively less methane than other wetland systems. Her research has spanned diverse systems, including geologic formations, hot springs, peatlands, and oceans. Across each, her central focus has been the carbon cycle—tracing the flows and storages that shape Earth’s climate future. She currently work as a data scientist with the USDA through The Cadmus Group, where she is helping develop an app to support the coherent, accessible entry of metadata for geospatial assets. Outside of her technical work, Cory is also a songwriter. Her music explores themes of climate, human nature, and bicycles (of which she’s written three songs at this point). One of her favorite lyrics—drawn from a conversation with her graduate school advisor Jeff Chanton—captures her scientific worldview: “Trees are like icebergs / they sit on a mirror, / reflecting the secrets beneath the veneer.”
Jeff Chanton received his PhD in 1985 at the University of North Carolina at Chapel Hill where he worked on the nearshore zone. He and his advisor, Chris Martens were greatly influenced by a lecture from the legendary Ralph Cicerone, which focused on the rapid increase in atmospheric methane, a powerful greenhouse gas, of which scientists had just become aware. Chanton then began working on methane transport and production from wetlands, peatlands, landfills and other environments. As a scientist, aware of our changing climate and its causes, he has observed the effects of climate change along the coastline and in the Arctic first hand. Chanton is a Lawton Professor at FSU and has published over 300 papers in the refereed literature. He has had the extreme good fortune to have benefitted by excellent students, collaborators and scientific colleagues.
Rachel Wilson is a biogeochemist whose research focuses on methane production in naturalenvironments spanning peatlands in northern Sweden to deep-sea methane seeps in the Gulf of Mexico. She holds a Ph.D. in Chemical Oceanography from Florida State University and was awarded a National Research Council postdoctoral fellowship in 2010 to study the stability constraints of methane gas hydrates, a potentially large marine methane reservoir. She is currently a research associate at Florida Sate University where she co-leads a number of research projects including this project which explores how climate change influences methane production in peatland ecosystems. Outside the lab, she explores waysto reduce carbon emissions through sustainable agriculture on her small farm, which integratespermaculture practices with a small herd of dairy goats to reduce the carbon footprint of food production.
Beth Holmes became fascinated by the use of stable isotopes to understand biogeochemical processes when she studied corals and estuarine systems as a graduate student in Bill Sackett’s lab at the University of South Florida. She earned her Ph.D. in 1996 from Bremen University in Germany, using carbon and nitrogen isotopes in deep sea sediments to reconstruct past nutrient utilization in the water column. More recently, Beth’s research has focused on methane and carbon dioxide production pathways in wetlands in the Everglades, Panama, and subarctic Sweden. Her work contributes to a growing body of knowledge aimed at better predicting how climate change may alter natural greenhouse gas dynamics.
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