Beyond one-size-fits-all: Refining forest restoration indicators for the Mediterranean context based on expert knowledge.

Abstract

Global and European forest restoration initiatives such as the European Nature Restoration Regulation (NRR) have set ambitious targets, but ensuring that restoration efforts translate into effective socioecological outcomes requires robust monitoring frameworks with appropriate indicators. However, the NRR's proposed indicators for forest restoration have raised concerns regarding the lack of socioeconomic considerations and their applicability across diverse forest contexts, including the Mediterranean. This study evaluates expert perceptions of thirty-four indicators (NRR, scientific literature, and socioeconomic ones) through a Delphi consultation with over sixty forest restoration experts from diverse disciplinary and sociodemographic backgrounds in Spain. Our findings reveal that deadwood (both lying and standing) accumulation was deemed the least relevant NRR indicator by experts (mean ± SD: 3.3 ± 1.2 on a Likert scale) due to concerns about increased wildfire risk, whereas native tree species dominance (4.3 ± 0.8) and tree species diversity (4.3 ± 0.9) were the most highly rated ones. Additionally, 93 % of experts agreed that socioeconomic indicators should be incorporated into restoration monitoring, with positive public perception of restoration (4.5 ± 0.8) being the most valued metric. Experts also highlighted the need for indicators assessing ecosystem resilience, such as natural regeneration, fire risk and soil erosion, which are currently absent from the NRR. Building on these insights, we propose a flexible, goal-oriented framework for selecting restoration indicators, balancing harmonization with regional adaptation, and highlighting indicators that evaluate multiple restoration goals. This approach aims to enhance the effectiveness of forest restoration monitoring in Spain and other southern European regions while contributing to the development of national restoration plans.