Ancient wetlands provide new insight into global carbon cycle

In the past, old buried peat sites acted as a carbon sink. Also nowadays, wetlands, such as bogs and fens, play a crucial role in the atmospheric carbon cycle.

Scientists from University of Helsinki and University of Eastern Finland have unearthed and pieced together evidence of more than 1,000 ancient wetland sites from across the globe, which are presently covered by fields, forests and lakes. Although vanished from the Earth’s surface, these buried sites could explain some of the differences between global carbon cycle models and real-life observations.

The discovery of widespread buried peatlands suggests that these layers of peat used to act as a kind of extra carbon trap in the global carbon cycle. The results also suggest that present-day wetlands may continue to offset rising atmospheric CO2 concentrations as the climate warms if they remain undisturbed by, for instance, drainage and fires.

“The fact that these peats are buried and stay in the soil is basically like a leak in what we usually consider a closed system of how carbon moves around the Earth, from the atmosphere to the soil and oceans. This new finding isn’t represented in our models of the global carbon cycle, and may help to explain previously observed inaccuracies in such models,” Dr Claire Treat from the University of Eastern Finland says.

Cliffs, quarries, road construction, and scientific sampling have revealed carbon-rich wetland deposits buried under other kinds of soil and sediments. Many wetlands are characterised by thick deposits of undecomposed plant material (or peat), which is often preserved, resulting in a record of wetland presence.

Buried wetland sites were found from the high Arctic islands of Canada and Siberia to tropical Africa and Indonesia, to southern South America and New Zealand. Some formed less than 1,000 years ago, while others formed during the warm climate period between the two latest glaciations more than 100,000 years ago.

University Researcher Minna Väliranta from the Ecosystems and Environment research programme at the University of Helsinki analysed peat samples from both Canada and Lemmenjoki in Lapland, Finland. Lemmenjoki is famous for goldmining and a find by a local goldminer turned out to be a buried wetland.

“The goldminer found an organic layer buried under moraine. He contacted Geological Survey of Finland (GTK) and they contacted me. We then went together to collect a sample.”

“Results of this study confirm my view that peatlands, have an important role in the atmospheric carbon cycle. They should be protected.” says Väliranta. At the moment, her research group studies arctic peatlands.

The study was led by Dr Treat at the University of Eastern Finland and by Dr Thomas Kleinen at the Max Planck Institute for Meteorology in Germany.

For further information

University Researcher Minna Väliranta, PhD, University of Helsinki, phone: 050 448 6483, email:

Dr Claire Treat (Postdoctoral Researcher), University of Eastern Finland, email:

Treat, C.C., T. Kleinen, N. Broothaerts, A.S. Dalton, R. Dommain, T.A. Douglas, J. Drexler, S.A. Finkelstein, G. Grosse, G. Hope, J. Hutchings, M.C. Jones, P. Kuhry, T. Lacourse, O. Lähteenoja, J. Loisel, B. Notebaert, R. Payne, D. Peteet, A.B.K. Sannel, J.M. Stelling, J. Strauss, G.T. Swindles, J. Talbot, C. Tarnocai, G. Verstraeten, C.J. Williams, Z. Xia, Z. Yu, M. Väliranta, H. Alexanderson, M. Hattestrand, V. Brovkin. Widespread global peatland establishment and persistence over the last 130,000 years. Proc. Proceedings of the National Academy of Science.

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