Signs of coastal bird community recovery over seven decades in three European seas

The ongoing biodiversity crisis, marked by global wildlife declines and high extinction rates that undermine ecosystem function and essential ecosystem services, is also evident in European marine ecosystems, where coastal birds have experienced marked population losses due to overfishing, habitat degradation, pollution, and decades of hunting. Despite conservation efforts and the establishment of protected areas, many species remain threatened. Numerous studies have assessed long-term population trends of individual coastal bird species; however, research addressing changes at the community level across broad temporal and spatial scales remains limited. Here, we used a large-scale database of 308 time series of coastal bird communities collected between 1957 and 2024 across the Baltic Sea, the North Sea, and the Western Mediterranean Sea to assess how abundance, taxonomic and functional diversity have changed over the past decades, and to evaluate the effect of conservation areas on coastal bird communities.

Our results showed overall increases in taxonomic richness (1.7% per year on average), taxonomic diversity (1.4%), abundance (2.7%), functional richness (4.1%) and functional evenness (0.7%) of coastal bird communities. However, trends were highly variable across sites, including 4.5% of them experiencing significant declines in species richness, 5.2% in taxonomic diversity, and 13.3% in abundance. Although these overall increases were similar across the three regions studied, they were not uniform within them. For example, recovery in the Western Mediterranean Sea occurred primarily between 1970 and 2000, while in the Baltic Sea, increases have occurred since 1995. Our results also showed the relevance of conservation areas for coastal birds, especially those strictly protected (i.e., IUCN Categories of Protected Areas Ia, Ib or II). However, we also found that some non-protected sites are recovering at rates similar to—or even exceeding—those observed in strictly protected areas.

Despite overall improving trends, many coastal bird communities continue to face persistent declines due to site-specific stressors and broader pressures such as overfishing, bycatch, habitat degradation, and climate change. Ensuring long-term conservation success will require not only well-managed protected areas and strict conservation policies but also strengthened monitoring, international collaboration, and adaptive strategies across European seas.