Contents lists available at ScienceDirect Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind Indicators on the ecosystem service “regulation service of floodplains” Ulrich Walz a, ⁎ , Benjamin Richter b , Karsten Grunewald c a Dresden University of Applied Sciences (HTW), Friedrich-List-Platz 1, 01069 Dresden, Germany b State Capital of Dresden, Environmental Office, P.O. Box 120020, D-01001 Dresden, Germany c Leibniz Institute of Ecological Urban and Regional Development, Weberplatz 1, 01217 Dresden, Germany ARTICLE INFO Keywords: EU Biodiversity Strategy Flood retention Mapping of ecosystem service Monitoring Prevention of flood damage ABSTRACT The capacity to absorb and retain surface waters in the floodplain in case of floods and thus prevent or reduce threats to settlement areas through flooding is an important aspect among others within the ecosystem service “Regulation service of floodplains”. Two simplified indicators for measuring the potential flood retention in Germany are proposed here: the “Area for flood retention” on the one hand and the “Proportion of built-up areas in the current floodplain” on the other. The results for the 79 largest rivers of Germany, which are also presented in the form of a map, show among other things that only around 35% of the morphological floodplain in Germany still serve for natural flood retention. In the short period between 2010 and 2015 alone, the area for flood retention decreased by 7.3 km 2 (0.13%) nationwide due to the increase in the settlement and traffic area. Capturing the ecosystem service of floodplains also for smaller rivers would make sense from a flood pro- tection perspective. It is also necessary to regularly capture any change of the current floodplain due to em- bankments and dyke relocations that currently cannot be deduced from available geodata. A political aim in Germany is to significantly increase the retention areas within the next few years. Our results show that huge efforts are necessary in order to reach this aim, which would directly contribute to the prevention of flood damage. 1. Introduction In Target 2, Action 5, the EU Biodiversity Strategy stipulates that the member States will map and assess the state of the ecosystems and their services and promote the integration of these values into the accounting and reporting systems at the EU and national level by 2020 (European Commission, 2011). Indicators for capturing and assessing such ecosystem services (ES) are required as an essential instrument of operationalisation and for measuring success. They are intended to provide information on ex- isting ES (including supply and demand) and on development trends as selected, readily comprehensible parameters. Currently, in Germany, the concept for such indicators at the na- tional level is being (further) developed on behalf of the Federal Agency for Nature Conservation (Grunewald et al., 2016; Grunewald et al., 2017). The classification of the ES was performed – as agreed in the MAES working group at the EU’s Directorate-General for the Environ- ment (European Commission, 2013) – according to the Common In- ternational Classification of Ecosystem Services (CICES) (Haines-Young and Potschin, 2013). In this paper, we present the coordinated in- dicators for the nationwide assessment of one class of the section “regulation & maintenance services”, namely “flood protection”. In the following we will refer to this as the ES “Regulation service of flood- plains” and describe it in more detail (Walz et al., 2017). 1.1. Description of the ecosystem service An important aspect of the ecosystem service “Regulation service of floodplains” is the capacity to absorb and retain surface waters in the floodplain in case of floods and thus prevent or reduce threats to set- tlement areas through flooding (Mehl et al., 2012; Stürck et al., 2014). This has a high relevance for society, since the risk of flooding poses a direct threat to human lives. Repeated flooding or even the risk alone can significantly limit the quality of life. Beyond this, it can cause huge economic losses. The risk for the occurrence of such events in built-up areas is growing due to an increase in impervious cover, less infiltration and climate change (European Environment Agency, 2010). Avoiding floods through the natural retention in the floodplain also contributes to avoiding significant costs of technical protective measures. On the one hand, the ES is determined by site-related and en- vironmental conditions. These include https://doi.org/10.1016/j.ecolind.2019.01.073 Received 9 February 2018; Received in revised form 16 January 2019; Accepted 29 January 2019 ⁎ Corresponding author. E-mail addresses: ulrich.walz@htw-dresden.de (U. Walz), brichter@dresden.de (B. Richter), k.grunewald@ioer.de (K. Grunewald). Ecological Indicators 102 (2019) 547–556 Available online 12 March 2019 1470-160X/ © 2019 Elsevier Ltd. All rights reserved. T