Ecology and Vulnerability

Leatherback Sea Turtle

Juvenile ocean-stage sea turtles (i.e., Green Sea Turtles (Chelonia mydas), Kemp’s Ridley Sea Turtles (Lepidochelys kempii), Loggerhead Sea Turtles (Caretta caretta) are projected to increase along the North Atlantic coast and in the Northern Atlantic Ocean based on simulated data from 1993 to 2017, making sea turtle conservation a priority along the Atlantic Coast due to climate change (Putman et al., 2020). A study testing phenological shifts of four sea turtles, two of which are RSGCN (Loggerhead and Green Sea Turtles), projected that phenological shifts will likely not be enough to overcome the negative impacts due to warming sands on nesting grounds and sea water temperature from climate change (Fuentes et al., 2024). As noted above, there were few studies found on the impacts of climate change on sea turtles in the northeastern U.S., therefore, many of the resources and information presented below are out of region but may provide useful context for how sea turtles are responding to climate impacts elsewhere and guide targets for similar studies for Northeast populations. 

Shifts in Range, Elevation, or Depth

Jellyfish (gelatinous zooplankton species) distribution and hotspots of high jellyfish abundance measured in the North Atlantic show overlapping hotspots of high abundance and habitat use by feeding Leatherback Sea Turtles, one within the Gulf of St. Lawrence (Nordstrom et al., 2020). Researchers hypothesized that since the waters are warming and jellyfish are shifting their range north, Leatherback Sea Turtles will do the same (Nordstrom et al., 2020).

Shifts in Phenology

Leatherback Sea Turtles may delay nesting due to cues like high temperatures in their foraging grounds, but the phenology of nesting was not changed due to temperature fluctuations at nesting sites (Neeman et al., 2015).

Changes in Population

Leatherback Sea Turtle reproductive success decreased by 19% following El Nino-Southern Oscillation (ENSO) in the Pacific during 2015-2016, showing how climate-induced increases in interannual climate variability harm this species (Tomillo et al., 2020). A simulation from nest temperature data between 1920-2012 at Playa Grande, Costa Rica, showed that Leatherback Sea Turtles' temperature-dependent sex determination can withstand warmer conditions. However, authors noted there might be a temperature threshold beyond which the sex would switch; the mean has thus far increased 1.2°C above the historical mean with no discernible change in sex ratio (Tomillo et al., 2015). In Costa Rica, nesting success was correlated with deeper nesting depths and lower nest temperatures; Leatherback Sea Turtles had the lowest nest success rate compared with Green Sea Turtles and Olive Ridley Sea Turtles (Santidrián Tomillo et al., 2017). Another study on temperature-dependent sex determination assessed the fitness and locomotion performance of Leatherback hatchlings associated with shaded (cooler) nests vs. unshaded (warmer) nests split across 48 clutches from 2013-2015 and found that shaded nests had higher hatching success and higher fitness (Rivas et al., 2019).

Even though shading increases nest success, it may still harm projected population trends under climate change. Researchers (Tomillo et al., 2021) simulated four 0.5 °C increments of temperature decrease under the current average temperature (30.4°C) and modeled Leatherback Sea Turtle populations 100 years into the future with climate scenarios increasing temperatures another four 0.5 °C. They found an overall population decrease because of the lower number of females in the population (Tomillo et al., 2021). Local hatchling output projected based on climate change projections were modeled in four regions, within the Atlantic sites were at Sandy Point NWR U.S. Virgin Islands and Pacuare Costa Rica in the Caribbean Sea; an increase in air temperature and a decrease in precipitation were correlated with a decrease in hatchling success (Santidrián Tomillo et al., 2015). The increase of climate-induced storms and tidal disturbances on beaches formed scrapes that prevented approximately 25% of Leatherback Sea Turtles from nesting high enough on the beach to avoid flooding events during a 2013-2014 study in Pacuare Nature Reserve, Caribbean Costa Rica (Rivas et al., 2016).