Carbon in agriculturally used peatlands in Poland

Peatlands are one of the most important terrestrial stores of organic carbon, but their drainage and years of agricultural use are leading to rapid carbon loss. Recent studies by IUNG-PIB and cooperating research centers indicate that in Poland, over a period of about 50 years, carbon stocks in peat soils have declined by an average of 65 percent, which translates into emissions of about 40 Mg of_CO2 per hectare per year.

Peatlands as a key store of organic carbon

Soils are the world’s largest terrestrial reservoir of organic carbon (Scharlemann et al., 2014). Thanks to their ability to sequester it, they play an important function in regulating the Earth’s climate (Frolking et al., 2011). Organic soils exhibit a particularly high capacity to store organic matter, which consists of 50-60 percent organic carbon.

According to the current Systematics of Soils of Poland (6th edition, 2019), they contain more than 12 percent organic carbon, or more than 20 percent organic matter. Organic soils are most often formed from peat, whose deposits are formed under conditions of permanent swampiness, where, in the almost total absence of oxygen, the rate of organic matter deposition is faster than the rate of decomposition. The organic carbon stock stored in peatlands is estimated at about 30 percent of the carbon stock stored by all the world’s soils, i.e. about 500-600 Gt (Parish et al., 2008; Yu et al., 2010), even though peatlands occupy only about 3.8 percent of the Earth’s land area (UNEP 2022). However, the drying of organic soils as a result of anthropogenic pressure and climate warming is turning them from carbon stores into sources of carbon dioxide (Leifeld et al., 2019).

Europe after drainage, or the scale of peatland transformation

In Europe after World War II, almost half of the area of peatlands was drained, mainly for agriculture. Poland belongs to a group of European countries, along with Germany, the Netherlands, Denmark and Ireland, where more than 80 percent of peatlands have been drained (Tanneberger et al., 2017; UNEP 2022). Most of these, about 75 percent, are used as permanent grassland, about 15 percent as arable land, and about 10 percent are set aside (Hare et al., 2025).

The use of peatlands under drainage conditions leads to a decrease in the organic matter content of the soil. This happens as a result of an increase in the rate of its decomposition due to aeration of the soil profile. As a result, organic soils, which contain more than 12 percent organic carbon, gradually transform into mineral-organic soils (6-12 percent organic carbon), and eventually into mineral soils (less than 6 percent organic carbon). Thus, the process of drainage can lead to the complete disappearance of organic soils, and thus peatlands.

Half a century of change – research results

The results of a study conducted by IUNG-PIB on agriculturally used soils of organic origin at 476 locations in Poland and compiled in cooperation with the research centers of URK, PŚ, SGGW and the University of Wisconsin (Hare et al., 2025) showed that carbon stocks in soils classified as organic in the 1970s have declined by an average of nearly 65 percent (from 762.2 Mg ^C-ha-1 to 269.3 Mg ^C-ha-1) over the past 50 years or so. This resulted in a decrease in the share of soils classified as organic by 30 percent (from about 65 percent to 35 percent), and a corresponding increase in the share of mineral-organic and mineral-organic soils by 4 percent and 26 percent, respectively.

The decline in the organic carbon content of soils has been accompanied by the shallowing of organic matter-rich horizons. At present, nearly 45 percent are shallow soils, in which the organic matter-rich horizon is no more than 50 cm thick, and soils where its depth is greater than 100 cm account for only 5 percent.

In the case of soils that have been transformed into organic-mineral and mineral soils over the course of half a century of drainage and use, there has been an inhibition of carbon losses, suggesting that a balance has been reached in these soils between losses and carbon input from the biomass of turf vegetation. In contrast, meadow and pasture use of organic soils does not compensate for carbon losses resulting from the decomposition of organic matter caused by their drainage (Hare et al., 2025).

The decline in carbon stocks in drained peatlands over 50 years allows an estimate of 40 Mg of_CO2 per hectare per year. The greatest losses are in central Poland, which has been affected by agricultural drought for many years, while in the northeastern part, which is wetter and cooler, carbon stocks have not changed or have increased (Hare et al., 2025). This indicates the importance of climate as an important factor affecting soil organic carbon stocks, the impact of which will be crucial to the success of plans to re-wet drained peatlands in agricultural areas.

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In the article, I used:

Frolking, S., J. Talbot, M. C. Jones, et al. 2011. “Peatlands in the Earth’s 21st Century Climate System.” Environmental Reviews 19: 371-396. https://doi.org/10.1139/ a11- 014.

Leifeld, J., C. Wüst- Galley, and S. Page. 2019. “Intact and Managed Peatland Soils as a Source and Sink of GHGs From 1850 to 2100.” Nature Climate Change 9: 945-947. https://doi.org/ 10.1038/s4155 8- 019- 0615- 5.

Parish, F., A. Sirin, D. Charman, et al. 2008. “Assessment on Peatlands, Biodiversity, and Climate Change: Main Report, Global Environment Centre.” Wetlands Internationa. 179.

Scharlemann, J. P. W., E. V. J. Tanner, R. Hiederer, and V. Kapos. 2014. “Global Soil Carbon: Understanding and Managing the Largest Terrestrial Carbon Pool.” Carbon Manaement 5, no. 1: 81-91. https://doi.org/10.4155/cmt. 13.77.

Tanneberger, F., C. Tegetmeyer, S. Busse, et al. 2017. “The Peatland Map of Europe.” Mires and Peat 19, no. 22: 1-17. https://doi.org/10.19189/MaP.2016.OMB.264.

UNEP. 2022. “Global Peatlands AssesSment – The State of the World’s Peatlands: Evidence for Action Toward the Conservation, Restoration, and Sustainable Management of Peatlands.” Main Report. Global Peatlands Initiative. United Nations Environment Programme, Nairobi, 418.

Yu, Z., J. Loisel, D. P. Brosseau, D. W. Beilman, and S. J. Hunt. 2010. “Global Peatland Dynamics Since the Last Glacial Maximum.” Geophysical Research Letters 37: L13402. https://doi. org/10.1029/2010G L043584.

Hare E., Smreczak B., Skalski T., Oleszczuk R., Ukalska-Jaruga A., Scharenbroch B.C.. 2025. “Changes in Soil Organic Carbon Stocks and Chemical Properties in Organogenic Soils Under Long-Term Agricultural Use in Central Europe, Poland.” Land Degradation & Development, 36:3756-3768. https://doi.org/10.1002/ldr.5597