Abstract Coastal areas are at the centre of human–nature relationship, shaped by recreation, tourism and aesthetic values. However, socioeconomic drivers of biodiversity change in coastal areas have received less attention. Soft sediment seafloors support diverse species communities and contribute to ecosystem functionality. One of the main threats is dredging, which sweeps resident organisms. Dredgings are commonly done to deepen waterways, but also for the purposes of private housing. The ecological impacts of these small‐sized dredgings are not well known over broad environmental and geographical gradients. We developed a simple approach for spatial integration of ecological and socioeconomic system, to describe how recreational land use change contributes to the loss of marine biodiversity. It shows how human behaviour, such as preference for a location of second home, can be derived from spatial data and coupled with ecological change. We characterize typical locations of second homes based on accessibility, aesthetics and environment, and with the information identified suitable areas for new second homes. We also quantified typical areas of dredging, based on the depth and substrate of the sea floor, and the extent of the reed beds, influencing the access to properties. We then simulate an annual increase of new second homes and expected land‐use change, namely dredging of shores. Finally, we quantified the realized and projected loss of marine biodiversity from dredged sites, based on species distribution models, relying on extensive ecological data collected from over 170,000 underwater sites. We found that small‐sized dredging can be detrimental to coastal biodiversity, as dredging targets shallow, photic bays and lagoons, with diverse algal and aquatic plant communities, with limited recovery potential. Dredgings also had broad impacts on benthic faunal habitats, which maintain ecosystem processes and functions. Our results reveal a significant ecological change driven by recreational land use. Reversing the trend of biodiversity loss requires a holistic understanding of socioecological systems. Our results highlight the need for integrating land–sea interactions into conservation policies and reforming current land‐use regulation for the benefit of marine biodiversity. Read the free Plain Language Summary for this article on the Journal blog.

Marine ecosystems are under high demand for human use, giving concerns about how pressures from human activities may affect their structure, function, and status. In Europe, recent developments in mapping of marine habitats and human activities now enable a coherent spatial evaluation of potential combined effects of human activities. Results indicate that combined effects from multiple human pressures are spread to 96% of the European marine area, and more specifically that combined effects from physical disturbance are spread to 86% of the coastal area and 46% of the shelf area. We compare our approach with corresponding assessments at other spatial scales and validate our results with European-scale status assessments for coastal waters. Uncertainties and development points are identified. Still, the results suggest that Europe’s seas are widely disturbed, indicating potential discrepancy between ambitions for Blue Growth and the objective of achieving good environmental status within the Marine Strategy Framework Directive.

Great cormorant Phalacrocorax carbo sinensis populations in the Baltic Sea have rapidly expanded since the 1990s, raising concerns about their ecosystem impacts. Nutrient runoff from colonies, as well as cormorant predation on fish, can affect surrounding producer communities. Past studies have found cormorant impacts on producers in the immediate vicinity of colonies, but the importance of cormorants over a larger spatial scale is unknown, especially compared to other environmental variables. We used an extensive underwater vegetation inventory dataset (~18000 data points along the Finnish coast) to determine the effects of cormorant colonies on macroalgae and plants. We compared community structure and species abundance/occurrence in near-colony (<5 km from a colony) and control (>10 km from a colony) points, and determined the importance of cormorant influence (using an index incorporating colony size and distance from the colony) in near-colony sites. We found no significant differences in community structure between near-colony and control points in most habitats, and adding the cormorant index only infinitesimally improved statistical models after incorporating other environmental factors. However, the abundance of several species did differ; in particular, the foundation species bladderwrack Fucus vesiculosus and eelgrass Zostera marina were either less likely to occur in near-colony points or were negatively correlated with cormorant index, possibly due to the effects of nutrient enrichment from colonies. Our findings confirm that cormorants can have effects on some producer species, but highlight that these effects are negligible when taking into account the scale and magnitude of other bottom-up and top-down processes occurring in the Baltic Sea.

This report presents for the first time in Europe an overview of anthropogenic pressures and their combined effects in Europe’s seas. The assessment covers the period of 2011-2016 but also presents how human activities and pressures at sea have changed over a longer time horizon. Practically the entire European marine area is under multiple pressures – such as hazardous substances, fish stock exploitation, climate change, underwater noise, non-indigenous species, seafloor damage, marine litter and nutrient enrichment. Shelf areas and coastal zone are affected by physical disturbance of seabed, eutrophication and non-indigenous species. The highest potential combined effects are found along coastal areas of the North Sea, Southern Baltic Sea, Adriatic and Western Mediterranean. The good news from this assessment is that many of the dangerous trends seem to have reversed. We have shown that the nutrient levels, hazardous substances, northern fish stocks and tuna stocks in the open seas show improvement. However, extensive pressures from several human activities still threaten the marine ecosystem, such as disturbance of seabed, and no trend reversal was seen in this assessment.