Recent trends in moisture conditions across European peatlands

Giese L; Baumberger M; Ludwig M; Schneidereit H; Sánchez E; Robroek BJ; Lamentowicz M; Lehmann J; Hölzel N; Knorr K; Meyer H

Abstract

Peatlands play a key role in climate change mitigation strategies and provide multiple ecosystem services, presuming near natural, waterlogged conditions. However, there is a lack of knowledge on how spatially heterogeneous changes in climate across Europe, such as the predicted increase in drought frequency in Central Europe, might affect these ecosystem services and peatland functioning. While analysis of peat cores and moisture sensors provide high-quality insights into past or present hydrological conditions, this information is usually only available for a limited number of locations. Satellite remote sensing is an effective method to overcome this limitation, providing spatially continuous and temporally highly resolved environmental information. This study proposes to use freely available data from the Landsat Mission to analyze trends in proxies of surface moisture of European peatlands over the last four decades. Based on a large random sample of peatland sites across Europe, we performed a pixel-wise trend analysis on monthly time-series dating back to 1984 using the Normalized Difference Water Index as a moisture indicator. The satellite-derived moisture changes indicated a pronounced shift towards wetter conditions in the boreal and oceanic region of Europe, whereas in the temperate, continental region, a high proportion of peatlands experienced drying. Small-scale patterns of selected sites revealed a high spatial heterogeneity, the complexity of hydro-ecological interactions, and locally important environmental and anthropogenic drivers affecting the moisture signal. Overall, our results support the expected effects of current climate trends of increasing precipitation in boreal northern and oceanic north-western Europe and increasing frequency of drought in continental Europe. Our fully reproducible approach provided new insights on continental and local scales, relevant not only to a better understanding of moisture trends in general, but also to practitioners and stakeholders in ecosystem management. It may thus contribute to developing a cost-effective long-term monitoring strategy for European peatlands.