Preserving the Last Stop of the Boreal: Kelp Forest Vulnerability in a Changing OceanClimate Change Refugia

Francisco Arenas¹, Dolbeth Marina1¹, Meyer Hugo¹, Sala Leiton Emilio¹, Chan Hernandez Sofia¹, Almeida Martinho¹, Franco Joao N.²

¹CIIMAR - Interdisciplinary Centre of Marine and Environmental Research, Portugal - ²MARE - IPLeiria, Portugal

Kelp forests are among the most emblematic coastal habitats, harbouring high biodiversity, with the capacity to provide several essential ecosystem services and support blue growth. Marine forests provide food, shelter and habitats for a variety of organisms such as apex predators (sea mammals and seabirds), fish, invertebrates and other seaweeds, and support complex food webs in coastal zones, promoting healthy artisanal fisheries. Additionally, the role of marine forests as a carbon sink has been highlighted as a climate change mitigation strategy. The coast of northern Portugal hosts the southernmost North Atlantic coastal kelp forests, dominated by several cold-adapted species, such as Laminaria hyperborea, alongside temperate species like Saccorhiza polyschides. The Iberian upwelling likely plays a crucial role in sustaining these northern communities by providing a climatic refuge. However, these vital marine forests face growing threats from global climate change and alterations in the dynamics of regional upwelling events. The BlueForesting project was designed to offer science-based guidance for developing and implementing nature-based solutions (NBS) to promote sustainable and resilient kelp forests in these resilient populations, serving as both mitigation and adaptation strategies to climate change. Our research has yielded critical insights into the structure, functioning, and ecosystem services provided by Europe’s southernmost kelp forests. We have quantified the size and current rate of habitat loss, tracked carbon stocks, and modelled fluxes to estimate these forests’ current carbon sequestration potential. Furthermore, we have conducted mechanistic species vulnerability assessments, identifying climate change refuges that could support the persistence of existing boreal kelp populations.