Manuscript and policy briefing evaluating success of large landscape-scale restoration (05/2025)

Key messages:

1. MERLIN monitoring confirms that well-designed Nature-based Solutions can deliver substantial environmental, social, and economic benefits, directly supporting European Green Deal objectives including biodiversity, climate resilience, and sustainable development.

2. Systemic, structured monitoring is essential for scaling restoration efforts. MERLIN’s approach provides decision-makers with the evidence needed to adjust interventions, allocate resources strategically, and ensure long-term effectiveness.

3. All 18 case studies completed structured reporting across Peatlands & Wetlands, Small Streams & Basins, and Large Transboundary Rivers, enabling comparative evaluation across landscape types and informing targeted governance responses.

4. Environmental outcomes were most robustly reported, particularly Biodiversity Net Gain and Climate Regulation. Gaps in socio-economic and sectoral criteria highlight the need for stronger integration of these dimensions into monitoring and planning.

5. A traffic light scoring approach combined impact direction and data confidence, providing a clear visual synthesis to support rapid decision-making and performance tracking.

6. High-confidence results were observed for Biodiversity Net Gain, backed by quantitative data such as 287 km of restored river stretches and 1,528 ha of rewetted or reconnected floodplain and wetland areas. Lower confidence for Zero Pollution and sectoral indicators signals priorities for improved data and methods.

7. Narrative insights complemented quantitative data in several cases, especially in complex settings. These enriched understanding of restoration outcomes and informed context-sensitive adaptation.

8. Trade-offs were reported, including temporary pollution increases and loss of agricultural land. Transparent identification of such tensions is critical for managing conflicts and aligning ecological restoration with socio-economic needs.