Potential effects of dune scarps caused by beach erosion on the nesting behavior of leatherback turtles

Beaches are constantly being reshaped by storms and tidal action; however, the increased frequency of storms and the sea-level rise due to climate change could cause loss of beaches that are vital breeding habitats for sea turtles. Here we evaluated the effects that erosion/accretion cycles have on the nesting behavior (nest site selection in relation to the presence of dune scarps) and nesting success (the proportion of nesting activities with oviposition) of leatherback turtles Dermochelys coriacea at Pacuare Nature Reserve, in Caribbean Costa Rica. Dune scarps accounted for over 20% of the beach, creating a barrier which prevented turtles from accessing the upper parts of the beach where nests would be safe from high tides and the storm line. About a quarter of the turtles, 24.1% (n = 20) in 2013 and 18.6% (n = 19) in 2014, did not crawl over scarps when they were present, regardless of their height, and laid their eggs below them. Additionally, during the period 2008 to 2014, the percentage of nests laid in high-risk areas significantly increased (R-2 = 0.91). The end result of the formation of scarps was that nests were laid in areas at risk of being flooded, threatening the survival of those eggs, and therefore the long-term population survival. Since sea levels have been rising significantly in the Caribbean between 1950 and 2010, and projections show a further increase throughout the 21st century, beach erosion may become an important threat not just for leatherbacks, but for many other endangered coastal species.