Monitoring long-term effects of climate change on intertidal rocky shores through citizen scienceLong-term Temporal Trends

Cam Ly Rintz^1,2, Bruno Serranito¹, Agathe Bouet³, Eric Goberville⁴, Isabelle Le Viol¹, Frédéric Ysnel^5,1, Eric Feunteun^1,2, Boris Leroy¹

¹Muséum National d’Histoire Naturelle, France - ²EPHE-PSL, France - ³Association Planète Mer, France - ⁴Sorbonne Université, France - ⁵Université de Rennes, France

Marine biodiversity is facing unprecedented global changes due to the phenomenon known as “Blue Acceleration”. Intertidal rocky shores, periodically submerged by tides, are highly vulnerable to climate change, as species already experience extreme daily variations and often live near their physiological limits, facing both marine and terrestrial impacts. The accessibility of these areas offers a promising opportunity for citizen science programs, which enable large-scale and long-term monitoring, essential for detecting and understanding global changes.

The ESPOIRS project aims at developing the citizen science program BioLit, launched in 2011, with the particular objective of monitoring the impacts of climate change on rocky shores, initially focusing on the coastal region of Brittany, France. To determine relevant locations for establishing monitoring time series — regular and repeated sampling over extended periods — we rely on four criteria:
– Areas already showing signs of changes in climatic conditions;
– Areas where significant climate changes are projected in the future;
– Areas where shifts in species distribution are expected to occur;
– Areas with citizen scientists willing to commit for the long term.

The first results allowed us to identify regions with contrasting patterns of observed and projected changes, using multiple metrics of climate change. For example, the western tip of Finistère has shown little warming in seawater since the 1950s, and future projections indicate no significant increase in temperature. In contrast, southern Brittany has undergone more pronounced warming, and the eastern part of Brittany is expected to experience the greatest temperature rises in the coming decades. These preliminary regions were discussed with BioLit participants to spot sampling sites. Finally, using a species distribution modelling approach, we also described the anticipated changes in rocky shore communities under changing climatic conditions.

This ongoing research will enable the establishment of targeted, large-scale, and long-term studies in collaboration with local communities, strengthening the link between science and society to provide valuable insights into the impacts of climate change on marine biodiversity.