ABSTRACT

Morisseau, S.; Jeanson, M.; Charroux, S.; Charpentier, M.; Paute, F.-E.; Viel, S.; Mercky, Y.; Chevallier, D., and Sucré, E., 0000. Multiscale impacts of beach morphodynamics on marine turtles: Implications for conservation.

Sea turtle nesting beaches are highly dynamic environments that evolve across various spatial and temporal scales. However, few conservation strategies integrate the need to understand and monitor the morphological dynamics shaping these habitats. This study, conducted in Mayotte, an island in the Mozambique Channel, explores the relationship between beach evolution and sea turtle nesting through a multitemporal approach aimed at improving nesting beach management. A long-term analysis of shoreline evolution, based on aerial imagery from 1950 to 2020, was conducted on 10 beaches. In the short term, topographic and hydrodynamic measurements were carried out between 2020 and 2022 on two primary nesting beaches, Grande Saziley and Papani, where sea turtles have also been monitored by local associations. The results indicate that (1) in the long term, morphological dynamics do not threaten the availability of the beach for nesting, and (2) in the short term, they regulate beach accessibility and the exposure of nests to erosion. On short term, these effects can result from chronic morphological changes or episodic morphogenic events. At Papani, seasonal morphological dynamics had a significant impact on nest accessibility and exposure to erosion, a beach located on the reef barrier with strong longshore dynamics and limited accommodation space, compared with Grande Saziley, a lagoon beach. This study highlights the importance of monitoring beach evolution as a key indicator in conservation strategies, also taking into account potential changes due to climate change.