Combined effects of soil multi‐contamination by metals and metalloids and drought slow down the ecological restoration of a Mediterranean scrubland

In Mediterranean ecosystems, soil contamination by metals and metalloids and drought represent major abiotic stresses whose combined effects on plant communities remain poorly understood, hindering effective ecological restoration practices. Here we evaluated the responses of plant community and species to combined stresses during a 4‐year ecological restoration operation in Mediterranean scrubland. We conducted monthly monitoring of plant communities across 20 restoration plots, analyzing taxonomic and phylogenetic diversity attributes alongside soil contamination levels and drought indices using mixed‐effects and hurdle models. Our results highlight that both stresses combined reduced taxonomic diversity and the diversity of distant lineages within the plant community by exerting a strong environmental filtering on species. Synergistic effects revealed that species richness decreased more strongly under high drought at low contamination levels than at high contamination levels, suggesting prior selection for tolerant species. Annual species were primarily impacted by drought through stress‐avoidance strategies, while perennial species were more affected by metal and metalloid contamination despite their stress‐tolerance mechanisms. Our findings highlight the importance of considering combined stress effects in restoration planning and identify phylogenetic diversity as a powerful criterion for species selection. Several perennial species, particularly Coronilla juncea , showed high tolerance and restoration potential for metal and metalloid‐contaminated Mediterranean ecosystems facing increasing drought under climate change.