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The Ecosystem Services (ES) concept has been acknowledged by scientists, policy-makers and practitioners to have the potential to support sustainable policy- and land-use decision-making. Therefore, a growing number of research activities are investigating the integration potential of the ES concept into real-world policy- and decision-making processes. These research activities are often confronted with conceptual challenges and methodological obstacles when applying different ES mapping approaches. This study is reporting those challenges encountered during a research project in Germany. In this research project, two urban regions, Rostock and Munich, were selected as case-study areas. In both urban regions, dynamic urbanisation processes occur across the urban administrative boundaries and threaten the supply of multiple ES in the periurban landscapes. The research project invited local stakeholders from the two urban regions to workshops and online meetings to discuss ES-related topics. For those events, maps visualising the spatial patterns of multiple ES were needed for communication and awareness-raising of the ES concept. We chose commonly used and relatively easy-to-apply mapping methods such as: (1) expert-based ES matrix approach, (2) simple GIS mapping with proxy indicators and data, and (3) simple ES models such as InVEST. We encountered several challenges during the mapping processes: The expert-based matrix approach provided valuable results for ES supply, but had limitations in assessing expert estimates for ES demand. Alongside other factors, evolving barriers related to the conceptual complexity of ES demand. Data unavailability/inaccessibility resulted in difficulties mapping all selected ES with proxy indicators at the targeted regional scale. So far, only a few individual ES can be modelled with InVEST models. Despite these challenges, the resulting maps were helpful for communication with local stakeholders. The discussions with stakeholders provided valuable insights into the future needs for ES research and identified existing barriers and challenges. We want to summarise and share our experiences and provide recommendations for future research on mapping ES supply and demand in urban regions.

Urban areas are mostly highly sealed spaces, which often leads to large proportions of surface runoff. At the same time, heavy rainfall events are projected to increase in frequency and intensity with anthropogenic climate change. Consequently, higher risks and damages from pluvial flooding are expected. The analysis of Flood Regulating Ecosystem Services (FRES) can help to determine the benefits from nature to people by reducing surface runoff and runoff peaks. However, urban FRES are rarely studied for heavy rainfall events under changing climate conditions. Therefore, we first estimate the functionality of current urban FRES-supply and demand under changing climate conditions. Second, we identify the effects of Nature-based Solutions (NbS) on FRES-supply and demand and their potential future functionality and benefits concerning more intensive rainfall events. A district of the city of Rostock in northeastern Germany serves as the case study area. In addition to the reference conditions based on the current land use, we investigate two potential NbS: (1) increasing the number of trees; and (2) unsealing and soil improvement. Both NbS and a combination of both are applied for three heavy rainfall scenarios. In addition to a reference scenario, two future scenarios were developed to investigate the FRES functionality, based on 21 and 28% more intense rainfall. While the potential FRES-demand was held constant, we assessed the FRES-supply and actual demand for all scenario combinations, using the hydrological model LEAFlood. The comparison between the actual demand and supply indicates the changes in FRES-supply surplus and unmet demand increase. Existing land use structures reached a FRES capacity and cannot buffer more intense rainfall events. Whereas, the NbS serve FRES benefits by increasing the supply and reducing the actual demand. Using FRES indicators, based on hydrological models to estimate future functionality under changing climate conditions and the benefits of NbS, can serve as an analysis and decision-support tool for decision-makers to reduce future urban flood risk.

People require multiple ecosystem services (ES) to meet their basic needs and improve or maintain their quality of life. In order to meet these needs, natural resources are exploited, threatening biodiversity and increasing the pressure on the Earth's ecosystems. Spatial-structural approaches are used to explain and visualise the spatial relationships and connections between areas that provide and benefit from ES. However, areas where the demand for these ES occurs are rarely considered in existing spatial approaches or equated with areas where people can use the benefits. In order to highlight the differences between these two areas, we would like to introduce the 'Service Demanding Area' (SDA) in an adapted spatial-structural approach. This approach relates SDA to already familiar ES provision and use units, namely Service Providing Areas (SPA), Service Connecting Areas (SCA) and Service Benefitting Areas (SBA) and can be used to schematically illustrate, understand and analyse the different forms of demand that can emerge. A literature review was conducted to provide an overview of the spatial mapping of ES demand. Three issues arose that should be addressed to improve the assessment of ES demand: 1) The term ES demand is not used consistently. To avoid confusion, it is important to clarify how ES demand is understood and how it differs from the other components of the ES concept (e.g. ES supply, ES potential, ES flow); 2) It is important to consider that ES demand is multi-faceted and is generated on different geographical scales, including the full range of stakeholders' perceptions, needs and desires which broadens the picture of societal demand for ES; 3) Meaningful interpretations between ES supply and demand need to be available to inform decision-makers about interventions for reducing ES trade-offs and mismatches.

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