Grey infrastructure or nature-based solutions? Stakeholder trade-offs and mapped hotspots in Costa da Caparica, Portugal

Abstract

Climate change and anthropogenic pressures are increasing risks to coastal systems, feeding the need for adaptation strategies that are both effective and socially accepted. Nature-based solutions (NBS) are gaining prominence for reducing risks while strengthening ecosystem resilience, but their implementation depends heavily on stakeholder acceptance. This study assesses local perspectives on coastal protection in Costa da Caparica, Portugal, a low-lying, densely occupied area exposed to erosion and flooding. Using a participatory framework, combining the Analytic Hierarchy Process with participatory mapping, five stakeholder groups, comprising residents, technical experts, and public authorities, evaluated decision criteria, preferred adaptation strategies, and gaps in current coastal protection. Results show that protection efficacy and maintenance costs were the most influential decision factors, while environmental co-benefits were less valued, particularly by residents. Although most groups favored NBS, the residents/businesses group preferred hard defenses, associating them with greater safety. Mapping revealed consensus that the urban front and camping site areas are underprotected, with recommended actions ranging from expanding dune restoration and nourishment to relocating vulnerable infrastructure and populations. Rather than claiming broadly generalizable preference rankings, this case study documents a transparent, transferable diagnostic workflow for already-managed coasts that links criteria weighting with mapped perceptions of underprotection to support socially responsive coastal planning.

The authors' abstract, as published at the source. Frontiers in Marine Science, 2026 · DOI ↗