Accounting for the value of ecosystem services of floodplains in Germany – National studies matter

Floodplains are among the most valuable and most threatened ecosystems. Worldwide, degradation and restoration are taking place at the same time. In Germany, more than 90% of the floodplains are degraded, and restoration is carried out through several projects because the benefits floodplains provide are already known, though not yet quantified. Decision makers and politicians are still in need of economic values, e.g. for cost-benefit analyses. Therefore, we sought to conduct a review of ecosystem services (ES) in German floodplains to provide a policy-relevant summary of estimated ES valuation efforts. While there are many reviews and meta-analyses in the scientific literature, they use data on an international scale. While international synthesis has value, assuming internationally synthesized values can be used to represent local or national values can be problematic due to unknowable transfer errors. In focusing on only German studies, we found that there were not enough data available for a German floodplain meta-analysis or review that could produce locally policy-relevant information. Only five floodplain ES were investigated in 14 studies between the years 2000 and 2021 within Germany, which provided enough data and study descriptions for a comparison of homogenized values. In total, ES of more than 4000 €2015/ha/yr were provided for German floodplains, which is much lower than global reviews, however, because of which and how ES are considered. There is an urgent need for representative studies examining how ecosystem values are generated and perceived to provide locally relevant information. There is a strong focus within meta-analytical studies on the international scale to overcome the data scarcity issue at the expense of local relevance. This is a fundamental trade-off that must be acknowledged.