Seasonal habitat dynamics and anthropogenic exposure of loggerhead turtles at a global scale.

Abstract

Loggerhead turtles (Caretta caretta) are highly migratory marine reptiles whose seasonal habitat shifts can alter their exposure to fisheries, vessel traffic, and plastic pollution. We combined global occurrence records with seasonal environmental predictors to build species distribution models (SDMs), mapped potential habitats for four seasons, and overlaid these habitats with fishing, shipping, and floating-plastic layers. We then compared cumulative exposure with the global marine protection network to identify conservation gaps. Potential habitats varied strongly among seasons and were associated mainly with sea surface temperature, mixed layer depth, and distance from shore. Fisheries exposure was concentrated in nearshore and continental shelf waters, shipping exposure followed major traffic corridors, and plastic pollution produced broader areal exposure. Multiple-pressure hotspots occurred consistently in the Mediterranean Sea, the northwestern Pacific, and the northwestern Atlantic. Existing marine protection covered only 11.2%-13.7% of cumulative exposure across seasons, indicating that the majority of cumulative exposure occurred outside the current marine protection network. These results show that seasonal habitat dynamics can substantially reshape anthropogenic exposure for a wide-ranging marine vertebrate. Integrating seasonal SDMs with pressure-specific exposure layers can help prioritize dynamic ocean management and transboundary conservation for loggerhead turtles.