Future sea-level rise impacts to Olive Ridley (Lepidochelys olivacea) and Green Sea Turtle (Chelonia mydas) nesting habitat on the Osa Peninsula, Costa Rica

Global sea turtle populations are in decline and so a global network of sea turtle nesting conservation programs have been established worldwide with the goal to protect vulnerable nesting mothers, and their clutches of eggs. Yet researchers have recently estimated that sea turtle nesting habitat is likely to suffer as a result of climate change and associated sea level rise. This study examines nest monitoring data from Costa Rica's Osa Peninsula with the aim to identify clutches located in suitable nesting habitat most susceptible to sea level rise and subsequent inundation. We analyze the impacts of six different sea level rise scenarios (from 0.25 m to 2 m) and discuss nesting inclinations and distributions of threatened Olive Ridley (Lepidochelys olivacea) and Green (Chelonia mydas) sea turtles on two beaches of the peninsula—known locally as Piro and Pejeperro. Sea-level rise scenarios on Piro beach indicated that 28.81% of the entire sample were likely to be inundated under a 0.25 m scenario, and 16.52% on Pejeperro beach. Under a more extreme, 2 m scenario, results indicated that 41.74% of nest sites on Piro and 24.55% on Pejeperro would be impacted. Results suggest that Olive Ridley turtles may be more susceptible to sea-level rise, based on their preferred nesting zones, commonly nesting closer to the tide line, as opposed to Green turtles that prefer to nest further from the tide line in vegetation zones where sea-level rise is likely to have less impact. Ultimately, the methodologies used in this study can support sea turtle conservation programs in assessing the potential effects of sea level rise and understanding nesting distributions on their nesting beaches, while also providing important insight in forecasting nest management and implementing monitoring techniques that may reduce the negative impacts associated with climate change and subsequent sea-level rise.