Study on the 2018 European drought

How did the land surface interact with the exceptional drought conditions of 2018 that resulted in crop failure, heat stress and low water in inland waters? Are some ecosystems better in fulfilling their role in the CO₂ and heat balance in such extreme circumstances? These questions were addressed by a freely available transnational data set of the new station network ICOS that provided information on half-hourly matter and energy fluxes for the year 2018 and for previous years for comparison. The ICOS network continuously measures the spatial distribution of greenhouse gas and energy exchange between the earth's surface and the atmosphere throughout Europe. IBG-3 contributes data of three stations to this network through the Helmholtz infrastructure TERENO. Analysis of this data resulted in a special issue of the journal "Philosophical Transactions of the Royal Society B". With a study based on 56 stations distributed over Europe led by Alexander Graf of the IBG-3 institute, it was shown that the heat release into the atmosphere was significantly higher than in previous years on average across almost all ecosystem types. The reason was that increased solar radiation did not lead to higher evaporation and thus cooling on average, since the lack of rain meant that water was not or only poorly available for plants. As a result, the average CO₂ uptake by the plants decreased. In normal years, this uptake compensates a considerable proportion of the CO₂ emissions associated with human activities and thus dampens the atmospheric increase in CO₂. Agricultural areas were hit hardest, while forests were least affected.

Graf, A., Klosterhalfen, A., Arriga, N, et al.: Altered energy partitioning across terrestrial ecosystems in the European drought year 2018. Philosophical Transactions of the Royal Society B, 375(1810), https://doi.org/10.1098/rstb.2019.0524.