Incorporation of climate effects in marine spatial planning. Possible Climate Refugia on the Swedish West Coast Based on Two Climate Scenarios

Abstract: Climate change poses a significant threat to the survival and distribution of marine species and habitats. Identification and conservation of climate refugia have emerged as a strategy to safeguard vulnerable habitats and promote species resilience. Refugia are areas with favourable conditions for species survival amidst changing climates, serving as vital havens for biodiversity and ecosystems. This study aimed to analyse the consequences of future climate scenarios on the distribution of blue mussel reefs, eelgrass beds, and sponge aggregations on the Swedish West Coast, and ultimately use this knowledge to identify potential climate refugia. Salinity and temperature were used as climate variables, where values were projected based on two climate scenarios, RCP 4.5 and RCP 8.5 and their respective model outcomes. The primary method used was analyses in GIS, based on geodata and previous research. The main findings revealed that these habitats will undergo alterations and retractions to different extents under different scenarios. The results showed that blue mussels and eelgrass refugia can be expected to be relatively similar to the current distribution, although with local exceptions where primarily salinity decreases had effects. Sponges were mainly impacted by temperature increases. However, decreasing salinity levels had a significant effect, as well. The distribution of sponges was altered to a larger extent compared to blue mussels and eelgrass, where refugia were primarily located in parts where salinity stayed high and temperatures low. The refugia using the species’ optimal limits are to a large extent safeguarded from the impacts of changing variables. Despite uncertainties and limitations, studying potential climate refugia is vital for understanding species distribution, informing MSP, and preserving marine ecosystems effectively.