Resumen de Mediterranean coastal marine biodiversity trends: an ecological and social assessment in the NW region
The Mediterranean Sea is one of the world's largest biodiversity hotspots, with high biodiversity levels concentrating in the coastal zone of the NW region, overlapping with large anthropogenic pressures. In this work, I use both historical ecological data and human environmental perception to assess changes and trends in the Mediterranean coastal marine habitats. This manuscript contains four empirical chapters. In the first chapter, I reconstruct the historical ecological trends of Corallium rubrum, a key engineering species of the coralligenous assemblages, which is considered a proxy for the habitat¿s overall health. Drawing on results from a meta-analysis of previous literature, I calculate yearly average values of C. rubrum basal diameter, height, and weight in the Catalan and Ligurian seas. In both areas, the selected morphometric parameters decreased until the 1990s, a decade marked by the exhaustion of coral harvesting banks and the Mediterranean trawling ban. C. rubrum morphometric parameters increased after the 2000s, reaching levels similar to the 1960s (Ligurian Sea) or 1980s (Catalan Sea). However, such results should be read with caution due to the scarcity of quantitative C. rubrum data before the 1990s, the concentration of research on few marine protected areas (including no-take zones), and the lack of recent data for unprotected colonies. The other three chapters assess social perceptions of the coastal marine habitats of a NW Mediterranean Marine Protected Area (Cap de Creus, NE Spain) using data collected through semi-structured interviews with local stakeholders and a survey to locals and tourists. The results are discussed considering findings from ecological data in the region. First, I assess social perceptions of the benefits, impacts and threats of coastal marine habitats. Overall, locals and tourists similarly perceived that coastal marine habitats provide valuable regulating services and they assigned less value to the cultural services. The impacts to the local coastal habitats most commonly perceived were marine pollution and climate change, which was also perceived as an important future threat. The harmful impact of people¿s behaviour towards the coastal habitat was expected to decrease in the future. Some perceptions were in line with the available scientific literature in the area. Cognitive biases (e.g., media influence on respondents¿ answers) seem to affect people¿s perceptions of biodiversity trends in coastal marine habitats. I then assess perceptions of local changes, focusing on environmental changes. Local stakeholders mostly reported economic changes, while environmental changes were less frequently reported. Changes were more often perceived as negative, where decrease in marine life and biodiversity was the most frequently reported trend among respondents. Results from the survey show a general perception of deterioration of the coastal marine habitats, for locals significantly more than for tourists. Finally, I present results from a survey to scuba divers in which they were asked to qualitatively assess the temporal health status change of Posidonia oceanica and C. rubrum in the region. Results indicate a decreasing trend for both species during the last four decades, especially notable for C. rubrum. Such trends are compared with the available scientific data and their similarities and mismatches are discussed. Overall, results from this work show the importance of combining ecological and social data in environmental assessments for future habitat management. Ecological data demonstrate an improving trend in protected C. rubrum¿s health status after having suffered a notable decrease. Social data suggest that people perceive an overall declining trend in the health of NW Mediterranean coastal marine habitats. Combining both types of data allows for a wider and better understanding of biodiversity changes and its potential societal implications, as well as helping define effective adaptation and biodiversity conservation strategies. Keywords: Anthropogenic impact · Cap de Creus · Coralligenous · Corallium rubrum · Environmental Perception · Global Change · Marine Historical Ecology · Posidonia oceanica
