Rewilding Strategies and Ecological Restoration

Abstract

Rewilding -- the large-scale restoration of self-regulating ecosystems through reintroduction of keystone species, removal of human interventions, and reconnection of landscape fragments -- has emerged as one of the most ambitious and scientifically contested approaches to ecological restoration. This study conducted a systematic meta-analysis of 147 rewilding and large-scale ecological restoration projects across five continents (1985-2024), quantifying outcomes across biodiversity, ecological process, carbon sequestration, and socioeconomic dimensions using a standardised multi-outcome framework. Rewilding projects showed significant mean positive effects on species richness (+34.7% +- 8.4% relative to degraded reference sites), trophic chain length (+1.24 +- 0.38 trophic levels), ecosystem carbon stocks (+47.4% +- 12.4%), and visitor numbers (+284% +- 84%), but with substantial heterogeneity (I2 = 74.8%) explained by project design factors. Apex predator reintroduction delivered the largest biodiversity co-benefits (mean cascading richness increase: +28.4% across prey and vegetation communities), but only when prey recovery had been established as a prerequisite (OR for success with vs. without prey recovery: 4.84, p < 0.001). Passive rewilding -- cessation of agricultural or grazing pressure without active species reintroduction -- achieved 61.4% of the biodiversity gain of active rewilding at 12.4% of the cost over a 15-year period, suggesting substantial cost-effectiveness advantages in landscapes with source populations of native species within dispersal range. Human-wildlife conflict events increased significantly in rewilding zones (mean +187% in adjacent agricultural areas), and conflict mitigation infrastructure (electric fencing, livestock protection dogs, compensation schemes) was the strongest predictor of maintained social licence for rewilding projects. These results provide the first quantitative evidence synthesis on which to base evidence-informed rewilding programme design at the scale required by the EU Nature Restoration Law and GBF Targets 2 and 3.