Drivers and Annual Totals of Methane Emissions From Dutch Peatlands

Rewetting peatlands is required to limit carbon dioxide (CO ) emissions, however, raising the groundwater level (GWL) will strongly increase the chance of methane (CH ) emissions which has a higher radiative forcing than CO . Data sets of CH from different rewetting strategies and natural systems are scarce, and quantification and an understanding of the main drivers of CH emissions are needed to make effective peatland rewetting decisions. We present a large data set of CH fluxes (FCH ) measured across 16 sites with eddy covariance on Dutch peatlands. Sites were classified into six land uses, which also determined their vegetation and GWL range. We investigated the principal drivers of emissions and gapfilled the data using machine learning (ML) to derive annual totals. In addition, Shapley values were used to understand the importance of drivers to ML model predictions. The data showed the typical controls of FCH where temperature and the GWL were the dominant factors, however, some relationships were dependent on land use and the vegetation present. There was a clear average increase in FCH with increasing GWLs, with the highest emissions occurring at GWLs near the surface. Soil temperature was the single most important predictor for ML gapfilling but the Shapley values revealed the multi-driver dependency of FCH . Mean annual FCH totals across all land uses ranged from 90 11 to 632 65 kg CH ha year and were on average highest for semi-natural land uses, followed by paludiculture, lake, wet grassland and pasture with water infiltration system. The mean annual flux was strongly correlated with the mean annual GWL (R = 0.80). The greenhouse gas balance of our sites still needs to be estimated to determine the net climate impact, however, our results indicate that considerable rates of CO uptake and long-term storage are required to fully offset the emissions of CH from land uses with high GWLs.