Sandy littorals under threat: a comprehensive review of the impacts of climate change on plant-dominated components relevant to the Mediterranean littoral active zone

Anthropogenic climate change, pollution, and biological invasions as climate mediated consequences are expected to dramatically affect directly and indirectly a variety of coastal habitats globally, in particular sandy littorals of the Mediterranean region. The active zone of these land-ocean transition systems (LAZ) comprises three connected entities, surf zone, beach, and foredune, which support biotic components, including habitat-forming species like seagrasses and dune plants contributing critically to coastal resilience. Most previous studies assessing how Mediterranean littoral ecosystems will change under climate scenarios have mainly focused on the effect of single climate-induced stressors on an isolated LAZ component at a time. A comprehensive understanding of the effects of multiple co-occurring stressors across LAZ key components is still lacking. This narrative review provides a literature overview of the effects of six main climate-induced changes expected in Mediterranean (warming, acidification, sea-level rise, salinity increase, alterations of precipitation patterns, and wind intensity/storminess) on key plant components of the surf zone (i.e., seagrasses), beach (i.e., wrack) and foredune (i.e., psammophytes). Our review underscores variable, even contrasting, responses of different components to some climate stressors and identifies critical knowledge gaps. Seagrasses are among the most investigated components while limited attention has generally been paid to wrack and psammophytes. The cumulative effects (additive, synergistic or antagonist) of multiple stressors on LAZ components are poorly understood. This review emphasizes the need to apply a holistic approach encompassing the cross-component linkages, multiple climate-related stressors, and their interaction with other anthropogenic stressors, like pollutants and beach management practices, in future studies on climate change impacts.