Peatlands occupy 3% of the global land area, but contain about 25% of the global soil carbon stock — equivalent to twice the amount in the world’s forests. And, that huge amount of carbon is not as secure as scientists once thought.
A multidisciplinary team of 69 scientists from around the globe published a paper on 7 December 2020 with a clear message: peatlands hold an enormous amount of carbon, are not as stable as previously thought, and must be fully accounted for in Earth system models.
The current study emphasizes importance of various disturbance elements, which make peatland C pool unstable and create challenges for modelling community. Disturbance processes are for instance permafrost dynamics, land-use and land-cover changes – including peatland restoration -, and fire. All these agents are missing from the predictive models.
Researchers from the University of Helsinki participated to this large synthesis by taking responsibility of writing chapters based of their own expertise. These were for instance permafrost thaw, nitrogen deposition and peatland management.
“It is clear that permafrost in Fennoscandia is in danger to thaw,” says Dr. Minna Väliranta from the Faculty of Biological and Environmental Sciences. “Potentially this leads to large increase in methane emissions to the atmosphere. However, the predictions of the future trajectories contain large uncertainties, thus more research is urgently needed.”
In Finland ca. 50% of the peatlands are impacted by human actions but more importantly, the scientists predict, that due to human actions especially in the tropics the carbon balance of peatlands will shift from a sink to a source in coming centuries and more than 100 billion tons of carbon could be released from peatlands by 2100, primarily because of anthropogenic impacts in tropical peatlands.
“That means that instead of absorbing carbon from the atmosphere, peatlands will instead release carbon and exacerbate climate warming, in a positive feedback loop,” said Dr. Julie Loisel, one of the main autohors of the peatland initiative.
“Overall message is that gradual drivers of change, such as temperature increases, water table drawdowns, sea-level rise, and nutrient addition, can also lead to rapid, nonlinear responses in peatland ecosystems,” points out Professor Atte Korhola from the Faculty of Biological and Environmental Sciences..
Loisel, J., Gallego-Sala, A.V., Amesbury, M.J. et al. Expert assessment of future vulnerability of the global peatland carbon sink. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-00944-0
Titled “Expert assessment of future vulnerability of the global peatland carbon sink,” and published in Nature Climate Change today, the paper combines existing research with survey estimates from 44 leading peatland experts. The authors also agreed that peatland science is a critical research area that needs further support to fully understand the peatland-carbon-climate nexus.
Finnish authors from the University of Helsinki, in addition to Väliranta and Korhola, were Docents Kari Minkkinen from the Faculty of Agriculture and Forestryand Sari Juutinen from the Faculty of Biological and Environmental Sciences, as well as Associate Professor Annalea Lohila from the Faculty of Science. Also Docent Tuula Larmola from the Natural Resources Institute Finland was involved.