Growing evidence suggests that forest management practices are threatening the long-term conservation of a number of animal, fungi, and plant species worldwide. Although unmanaged forests are considered important for biodiversity, forest management continues to affect these vital habitats. We systematically reviewed the scientific literature to gain insight into the effects of forest management abandonment on biodiversity. We calculated log response ratio effect sizes to perform a meta-analysis on species richness between still managed (MAN) and no longer managed (NLM) forests, throughout the world's boreal and temperate forest ecosystems. Our statistical approach included improvements relative to a rigorous treatment of pseudo-replication, an objective choice of taxonomic resolution, and new forms of residual heterogeneity. In our simplest model, plant species richness was significantly lower in NLM than in MAN stands (−14.7 %), while fungi (+10.2 %) and animal (+10.6 %) richness were higher in NLM sites but not significantly (at the 5 % level). Models were improved by adding precipitation, time since abandonment of management (TSA), and their interaction. Effect size estimate for total species richness in NLM forests significantly increased with TSA in wetter climates (+14.3 %), but decreased with TSA in drier climates; fungi richness (+18.1 %) became significantly higher in NLM. These results underline the taxa-dependent responses to management abandonment as well as the slow but real context-dependant recovery capacity of biodiversity after management abandonment. Our findings support the call for further coordinated research to confirm identified patterns, then context-relevant policies aiming to set aside forest zones in production forest systems for conservation purposes.