Review finds non-monetary ecosystem-service assessments can guide floodplain nature-based solutions across Europe

A review of non-monetary ecosystem-service assessment methods found that comparable, quantitative evaluations can help identify priorities for conserving and restoring European river floodplains at basin, regional and local scales. Drawing on three case studies—the Danube River Basin, the River Nebel in Germany and Serbia’s Koviljsko-Petrovaradinski Rit Special Nature Reserve—the authors show how these tools can support management decisions, reveal trade-offs and assess the performance of nature-based solutions.

The review synthesises existing literature and the authors’ experience with European floodplain assessments rather than generating new empirical data. It focuses on the River Ecosystem Service Index, or RESI, which was developed in Germany to assess 18 provisioning, regulation and maintenance, and cultural ecosystem services, and on its international extension through the IDES project, which provides schemes for 26 services in the Danube River Basin. Both approaches classify the performance of individual services on a five-level scale and allow results to be mapped for floodplain segments between 1 and 10 kilometres wide.

Floodplains are described as hotspots of regulating services, including flood-risk reduction, drought regulation, nutrient retention, sediment regulation, cooling and carbon sequestration. They can also supply provisioning services such as drinking water, fish, agricultural products and plant biomass, as well as cultural services including recreation, knowledge systems and cultural heritage. Natural heritage is also identified as a common ecosystem service, rather than a service unique to wetlands. The provision of floodplain-specific and high-performing services depends strongly on river pulses and is generally greater in intact or restored floodplains than in degraded ones.

The reviewed nature-based solutions include conserving functioning rivers and floodplains, relocating dykes, removing embankments and allowing channels to meander, reconnecting oxbow lakes and flood channels, restoring extensive grassland and forest use, removing weirs, retaining or adding river wood, stopping drainage and widening river channels. These measures can re-establish hydro-morphological processes and longitudinal, lateral, vertical and temporal connectivity. Reported effects vary by service and site: restoration may support several regulating and cultural services while reducing arable crop production or plant biomass under changed hydrological conditions.

At basin scale, the review evaluates 14 ecosystem services across the 817,000-square-kilometre Danube River Basin using IDES and examines their association with eight standardised indicators of human pressure. The MuFu multi-functionality index compares services scoring below 4 with those scoring 4 or 5. Lower and middle Danube floodplains showed the greatest multi-functionality, supporting priority for conservation, while parts of the Yantra, Tisza and upper Danube had lower scores and greater scope for pressure mitigation. Land-use intensity, impoundments and river morphological alteration showed the strongest relationships with assessed service performance, although their effects varied regionally. The analysis identifies associations rather than establishing that every pressure directly caused the observed pattern.

At regional scale, the River Nebel case compares conditions before restoration with those after interventions conducted from 1990 to 2016. About 22 kilometres of river and floodplain were restored at a cost exceeding €7 million. Using RESI, the review reports that 35 of 43 one-kilometre segments showed increased performance in the evaluated services, and the summed score for seven regulating services rose by as much as 17 points. The assessed changes included an approximately 17% increase in flood-retention area, equivalent to about 119,000 cubic metres of water, a nearly 20% reduction in greenhouse-gas emissions from formerly intensively used peatland soils, and more than 12% greater cooling capacity of water bodies and soils.

The Nebel assessment also illustrates the review’s limitations. It relied on different databases for the 1990 and 2016 conditions, evaluated no provisioning services, and could not attribute every change to restoration; declining water levels in some peatland areas, for example, were associated with climate effects and sedimentation independent of the project. Monetary estimates also depended on replacement-cost and damage-cost assumptions. Under the cited methods, reductions in flood risk and greenhouse-gas emissions were estimated to amortise the approximately €7 million investment within four to 10 years, but the result varied with the damage-cost approach used.

At local scale, the Koviljsko-Petrovaradinski Rit reserve in Serbia covers 5,886 hectares on both banks of the Danube near Novi Sad. More than 40 stakeholders helped identify ten priority ecosystem services, five important pressures and five potential mitigation measures, then co-designed status-quo, ideal and realistic “optimal” scenarios. A fuzzy cognitive model mapped relationships among services, pressures and measures. The study found low availability of four selected services under current conditions. The ideal scenario improved all assessed services to good or very good conditions, while the jointly designed optimal scenario also improved them while accounting for differing stakeholder needs, rights and preferences.

Overall, the review concludes that standardised ecosystem-service assessments can help planners compare locations and scenarios, prioritise conservation, restoration or pressure reduction, monitor restoration outcomes and identify synergies and trade-offs. Their usefulness depends on matching the spatial scale and resolution to the decision, integrating local participation, conserving functioning floodplains and addressing competition among agriculture, urban development, infrastructure, flood protection and navigation. The authors caution that no single assessment or measure is universally appropriate: the appropriate nature-based solution depends on the project’s objectives and its ecological, socio-economic and hydrogeomorphological context.

Subject of Research: Review of non-monetary ecosystem-service assessment for nature-based management of European river floodplains

Article Title: Assessing ecosystem services across scales to support nature-based solutions in river floodplains: a review of non-monetary tools

Article References: Stammel, B., Jähnig, S. C., Mehl, D., Pusch, M., Srđević, Z., Tschikof, M., Wulf, S., & Scholz, M. (2026). Assessing ecosystem services across scales to support nature-based solutions in river floodplains: a review of non-monetary tools. Nature Conservation, 62, 95-119. https://doi.org/10.3897/natureconservation.62.148716

Image Credits: AI Generated

DOI: 10.3897/natureconservation.62.148716

Keywords: river floodplains, ecosystem services, nature-based solutions, non-monetary assessment, Danube River Basin, River Nebel, floodplain restoration, multi-functionality, stakeholder participation, wetland management, Assessing, ecosystem