Greenhouse gas management in European land use systems - Teilprojekt peatland synthesis (GHG Europe)

The GHG‐Europe project aimed to improve our understanding and capacity for predicting the European terrestrial carbon and greenhouse gas budget. The project attributed the fluxes of CO2, N2O and CH4 in European land ecosystem to human versus natural driving factors. Updates of the European carbon and greenhouse gas budget confirmed the previously published values. Europe remains a net carbon sink, which is more than compensated by N2O and CH4 emissions from agriculture. These updates do not fully include yet the greenhouse gas (GHG) sources from drained organic soils (peat soils). Despite a high uncertainty in the area and drainage status anthropogenic emissions from drained organic soils are likely underestimated by at least factor two or three in the European greenhouse gas inventory under the United Nations Framework Convention on Climate Change. For the first time, European estimates have been made based on fully consistent in spatio‐temporal driver fields with common time periods, frequency, and spatial resolution. New driver fields have been developed for important direct and indirect human drivers: nitrogen deposition, agricultural management, and age class distribution in forests. The driver fields are publically available for further use at the project database. The classical approach to constrain the terrestrial carbon and greenhouse gas budget by independent topdown and bottom‐up methods has again been successfully applied at European scale. The application at regional scale, however, revealed considerable uncertainty in the atmospheric top‐down method so that so far, only the bottom‐up method was considered robust to monitor success in GHG mitigation at regional scale. Management effects override the impact of interannual variability in climate drivers on the ecosystem carbon balance when more than 20% of the net primary production is harvested. This threshold is likely exceeded in most land‐use systems and regions of Europe except for pastures and young forests. Land‐use changes have occurred on 25% of the European land area since 1900 and on 15% since 1950. There is a strong asymmetry in soil reactions to land‐use change. Soils lose carbon fast within 20 years but take more than 100 years to recover. The long legacy of land‐use change effects on soil carbon may mask effects of recent management changes. Sensitivity and attribution analyses based on data synthesis and modelling agreed in the most effective options for GHG mitigation. They confirmed previous scientific findings and policy recommendations for mitigation measures in croplands, grasslands, forests and managed peatlands. Scenarios of future carbon and GHG emissions were developed. They demonstrate the importance of consistent cross‐sectoral policies for agriculture, energy and other fields that affect land‐use decisions so that clear incentives for low emission land‐use systems can be set up. Land‐use decisions, economic and political drivers will remain the dominant drivers of European carbon and greenhouse gas fluxes in the coming decades.