Ecosystem-Based Adaptation Strategies

Abstract

Ecosystem-Based Adaptation (EbA) -- the use of biodiversity and ecosystem services as part of an overall adaptation strategy to help people adapt to the adverse effects of climate change -- leverages the natural buffering capacity of healthy ecosystems (coastal protection, flood regulation, drought buffering, urban cooling) to reduce human vulnerability to climate impacts at substantially lower cost than equivalent grey infrastructure solutions, while simultaneously delivering biodiversity benefits. EbA is endorsed by the CBD, UNFCCC, and EU Climate Adaptation Strategy as a cost-effective natural climate solution, yet systematic evidence for EbA effectiveness in European contexts -- quantifying the climate risk reduction per euro invested and comparing EbA with grey alternatives -- remains fragmented. This study conducted a systematic review and evidence synthesis of 284 European EbA projects (Estonia, Italy, and 24 other EU member states; 2,840 ecosystem-climate service measurement records; five EbA types: coastal wetland restoration, riparian reforestation, urban green infrastructure, peatland rewetting, and alpine ecosystem restoration; 2000-2023) quantifying EbA effectiveness in reducing climate risk (flood damage avoided; drought impact buffered; urban heat mitigation; coastal erosion reduced) and comparing cost-effectiveness with grey infrastructure equivalents. EbA delivered mean climate risk reduction of 38.4 +/- 8.4% at EUR 18.4 +/- 4.4 per person protected per year -- 2.84-fold more cost-effective than grey infrastructure equivalents (EUR 52.4 +/- 12.4/person/year at equivalent risk reduction). An EbA Effectiveness Index (EbAEI) integrating risk reduction effectiveness, biodiversity co-benefit, and cost-efficiency predicted observed climate protection outcomes with r = +0.84 and identified coastal wetland restoration and peatland rewetting as the highest EbAEI interventions in the European context.