Monitoring the drought resilience of near-natural peatlands by means of SAR remote sensing

Peatlands have been intensively used for centuries either for peat extraction, agricultural usage or forestry. The related drainage has led to falling water levels, altered microbial activity and the associated greenhouse gas emissions, the shrinkage of the peat layer and an overall degradation of peatland areas causing the disruption of these ecosystems. Lately, some areas have been restored and brought back to a semi-natural state by prohibiting their use and lifting the water table.

To monitor shrinkage and swelling processes of the peat layer, we applied the Persistent Scatterer Interferometry (PSI, Ferretti et al. 2001) to several upland peatlands south of the city of Munich, Germany, for the period 2015-2018. This technique uses time-series of Synthetic Aperture Radar (SAR) satellite images from the Sentinel 1A and 1B platforms, to monitor potential surface deformation caused by swelling and shrinkage of the peat layer due to water content.

The presentation will show the captured seasonal height fluctuations peatland areas are naturally subject to. The overall trend for the observation period shows a subsidence for most investigated peatlands. Furthermore, we could observe a strong negative trend over most study areas throughout the year 2018. This is expectedly related to the extremely dry conditions in 2018 in this part of Europe which caused the peat layer to dry out and to shrink.

The results illustrate how peatlands react to dry periods. The question remains how resilient peatlands are to droughts, particularly when considering that dry periods may occur more often in the future. In consequence, the findings will also be instrumental to assess the climate mitigation potential of rewetted peatlands. By means of PSI it is possible to monitor surface changes over long time frames and assess the long-term vulnerability of natural and restored peatlands to climate change.

The work presented here is part of the KliMoBay project, funded by the Bavarian State Ministry for the Environment and Consumer Protection through the European Regional Development Fund (ERDF).

Ferretti, A.; Prati, C.; Rocca, F. (2001): Permanent scatterers in SAR interferometry. IEEE Trans. Geosci. Remote Sensing 39 (1), S. 8–20.