However, according to research published in the journal Global Change Biology, the recovery of these bird communities has not been homogeneous. In fact, in 5% of the areas studied, species richness continues to decline and in 13% of others the number of individuals remains in recession. "Recovery has also been uneven over time. In the Baltic Sea, the most pronounced improvement occurred between 1990 and 2015, with significant increases in species number and abundance. In the North Sea, with less data available, stocks appear to be more stable. On the contrary, in the western Mediterranean, the improvement occurred mainly between 1970 and 1990 and subsequently this trend stagnated", explains Carlos Cano-Barbacil, researcher at the National Museum of Natural Sciences (MNCN) and first signatory of the work.
Although the recovery of Mediterranean seabird populations is primarily associated with the legal protection of their breeding grounds, the results also show a recovery in unprotected sites at a rate similar to that of strictly protected areas. For example, populations of seabirds rearing in the ports of Valencia and Castelló showed high rates of change in the number of breeding species (3.4% per annum), diversity (5.1%) and especially the abundance of breeding birds (37.9% per annum).
"Threatened species such as the Audouin’s gull and or the common tern have been successfully established in these ports during the last decades by the existence of fences or restrictions of access to people, as well as the general absence of terrestrial predators associated with the lack of connection of these areas with natural habitats, so that birds have found in these places the tranquility they need to reproduce successfully", said Miguel Ángel Gómez Serrano, researcher from the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBiBE), located in the academic scientific area of the University of Valencia Science Park, also participating in the study.
Birds inhabiting beaches, cliffs, estuaries and small islands play a key role in the functioning of coastal and marine ecosystems. However, they are also one of the groups most threatened by overexploitation of the seas, pollution, climate change, loss of breeding grounds and invasive species such as rats or cats.
"Threatened species such as the Audouin’s gull and or the common tern have been successfully established in these ports during the last decades by the existence of fences or restrictions of access to people, as well as the general absence of terrestrial predators associated with the lack of connection of these areas with natural habitats, so that birds have found in these places the tranquility they need to reproduce successfully", said Miguel Ángel Gómez Serrano, ICBiBE researcher
The results of the study confirm that European policies, such as the Birds Directive and the creation of protected areas, have paid off. However, the authors warn that threats such as coastal transformation, overfishing, pollution, invasive species or climate change still persist. "These birds are indicators of ecosystem health and their recovery in some places is the result of decades of conservation efforts, but we cannot let our guard down," warns Cano-Barbacil.
The team collected data from 1957 to 2024, and applied statistical models to assess changes in species richness and diversity as well as abundance of individuals. In addition, the effect of protected areas was analysed and trends in breeding and winter bird communities were compared, supporting research on European databases and national censuses.
This work is part of the European project MARCO-BOLO (Marino COastal BiOdiversity Long-term Observations) in which also participate the universities of Valencia and Murcia and the Center for Advanced Studies of Blanes (CEAB-CSIC).
Source: UV News