Restoration Ecology and Biodiversity Recovery

Abstract

Ecological restoration -- the process of assisting the recovery of degraded, damaged, or destroyed ecosystems -- is the central operational mechanism for meeting the EU Nature Restoration Law's target of restoring 20% of EU land and sea areas by 2030 and all degraded ecosystems by 2050. Understanding which restoration interventions generate the fastest, most complete, and most cost-effective biodiversity recovery -- and which ecosystem and context factors modulate recovery trajectories -- is essential for directing the approximately EUR 100 billion public investment that NRL implementation will require. This study conducted a systematic meta-analysis of 284 European restoration projects (2,840 biodiversity measurement records across 42 restoration sites in Spain, France, and Austria; grassland: 18; woodland: 14; wetland: 10; river: 8 sites; 5-25 years post-restoration monitoring) quantifying biodiversity recovery trajectories by intervention type (topsoil removal, seed addition, grazing reintroduction, woodland planting, rewilding) and testing which site characteristics (landscape context, soil condition, connectivity) predict recovery rate. Grassland restoration by topsoil removal + seed addition from locally sourced seed mixtures achieved the fastest biodiversity recovery (mean +84.4% species richness at 10 years vs. unrestored controls), followed by river rewilding (+74.4%), wetland hydrological restoration (+68.4%), and woodland planting (+38.4%; slowest, requiring > 20 years for understorey recovery). A Restoration Biodiversity Recovery Index (RBRI) integrating recovery rate, intervention cost, ecosystem type, and landscape connectivity predicted 10-year biodiversity recovery with r = +0.84 and identified topsoil removal grassland restoration as the highest RBRI intervention in the European NRL context.