Enhanced but highly variable biodiversity outcomes from coastal restoration: A global synthesis

Coastal ecosystems are being restored to combat environmental degradation and biodiversity loss. Colonization of restored sites by non-habitat-forming animals improves outcomes for ecosystems and society, yet there has been no review of how animals respond to coastal restoration. Here, we extracted 5,133 response ratios from 160 studies to show how coastal ecosystem restoration benefits animals as individuals, populations, and communities. Abundances and diversity at restored sites were greater than at degraded (61% and 35%, respectively) and unstructured (42% and 37%) control sites and similar to those at natural reference sites (both within 2%). Individuals in restored sites were similar in condition to those within control and reference sites. However, responses among projects were highly variable and rarely related to restored site maturity or characteristics, presenting a challenge for predicting outcomes and highlighting the need to improve restoration techniques, monitoring, and reporting. Nevertheless, studies so far suggest coastal restoration benefits biodiversity.