Sea Turtles and Climate Change
Sea turtles are ancient survivors. They've weathered more than 100 million years of change on Earth, including the Ice Age, continental drift, rising and falling oceans, and the extinction event that killed the dinosaurs. But today, climate change is happening at a pace that is unlike anything in their evolutionary history, and researchers are concerned about its impacts as they watch them unfold in real time. In this post, we'll walk through the main ways that climate change is impacting sea turtles and provide links to where you can learn more about this topic.
We've also put together a short video about sea turtles and climate change as part of our Sea Turtles: Deep Dive series – watch it below!
Overview: Sea turtles and climate change
Having lived on Earth for more than 100 million years, sea turtles have survived through many changes in the climate, including temperatures both warmer and colder than today, and multiple periods of warming and cooling. Yet today, Earth’s climate is warming 10 to 45 times faster than the warming cycles of the past due to increased carbon dioxide in the atmosphere and other human activities. And this pace is only continuing to accelerate, with temperature rise having nearly doubled from around 0.20°C per decade (1970–2015) to approximately 0.35°C per decade over the past ten years.
The impacts of climate change on sea turtles are being actively studied by scientists worldwide. Some impacts are well documented, while others are still unknown. Based on what is already known, climate change is considered to be among the biggest threats sea turtles face, because it impacts every part of their life cycle, from embryo to adulthood, and it doesn't act alone: it layers on top of existing pressures like fisheries bycatch, coastal development, direct take, and pollution, pushing some populations closer to the edge of what they can handle.
How is climate change affecting sea turtles?
Climate change is known to impact sea turtles in three major ways:
Warmer sand is changing hatchling sex ratios and impacting development. A sea turtle's sex isn't determined by genetics. Instead, it's determined by the temperature of the sand around its egg during its development. Warmer sand produces females; cooler sand produces males. As global temperatures rise, nests are trending hotter, and populations are producing far more females than males. At Raine Island, Australia, the world's largest green turtle nesting site, researchers have found that more than 90 percent of hatchlings are now female, a pattern that's held since the early 1990s. And when sand gets too hot, embryos can experience developmental stress or even die (read more here).
Rising seas and stronger storms are damaging nesting beaches. Sea turtles lay their eggs on tropical and subtropical beaches worldwide, an essential stage in their life cycle. Climate change is making storms more intense and causing global sea level rise to accelerate, and both of these changes can impact nesting beaches by causing sand erosion or accretion, flooding/nest inundation, and even making entire nesting beaches disappear. For example, on St. Catherines Island, Georgia (USA), scientists have tracked the shoreline losing about three meters of beach every year; within a decade, the portion of beach suitable for nesting dropped from 25 percent to just 12 percent. And nests that get flooded repeatedly by storms and high tides can lose up to 77 percent of their hatching success. At the same time, some communities are trying to address beach loss through efforts like sand renourishment and beach armoring, which can make beaches less suitable (or unsuitable) for sea turtles to nest.
Sea turtle habitats are shifting. As oceans and coastlines shift, sea turtles are expanding into habitats that were once too cold for them — from Peru to the Mediterranean. That range expansion isn't always safe: each fall, hundreds of turtles, mostly endangered Kemp's ridleys, get trapped in Cape Cod Bay, Massachusetts, as they try to migrate south, and strand on the beach when the water turns too cold. Cold-stunning events have topped 1,200 turtles in a single season. In addition, sea turtles are nesting on new beaches where they are sometimes less protected or are coming into conflict with human uses.
Other impacts of climate change on sea turtles are still being studied, such as the impacts on sea turtles’ feeding habitats, like seagrasses and coral reefs.
None of these impacts happen in isolation. Climate pressures stack on top of bycatch, pollution, and coastal development — and turtle populations already weakened by those threats are less able to adapt.
What's being done to help sea turtles cope with climate change?
Conservationists around the world are working to help sea turtles weather these changes: relocating at-risk nests to safer, higher ground; shading and cooling nests to bring down incubation temperatures; and rescuing and rehabilitating cold-stunned turtles before it's too late. Long-term monitoring programs like State of the World's Sea Turtles (SWOT) program are also critical, giving researchers and practitioners the global data they need to understand how these threats are unfolding and where to focus conservation efforts.
What can I do about climate change?
The good news is that you can be part of the solution. Reducing your carbon footprint, supporting policies that cut emissions, and backing organizations working to protect nesting beaches and fund on-the-ground conservation all make a difference. Support SWOT's sea turtle conservation work to help turtles build the resilience they need to navigate the next century and beyond.
Where can I learn more about sea turtles and climate change?
Explore the following resources to learn more about sea turtles and climate change
Scientific publications:
Jensen, M. P., Allen, C. D., Eguchi, T., Bell, I. P., LaCasella, E. L., Hilton, W. A., Hof, C. A. M., & Dutton, P. H. (2018). Environmental warming and feminization of one of the largest sea turtle populations in the world. Current Biology, 28(1), 154–159. https://doi.org/10.1016/j.cub.2017.11.057
Pike, D. A., Roznik, E. A., & Bell, I. (2015). Nest inundation from sea-level rise threatens sea turtle population viability. Royal Society Open Science, 2(7), 150127. https://pmc.ncbi.nlm.nih.gov/articles/PMC4632582/
Shaw, C. (2013). Effects of inundation on hatch success of loggerhead sea turtle (Caretta caretta) nests [Master's thesis, University of Miami].
Hochscheid, S., Maffucci, F., Abella, E., Bradai, M. N., Camedda, A., Carreras, C., Claro, F., De Lucia, G. A., Jribi, I., Mancusi, C., Marco, A., Marrone, N., Papetti, L., Revuelta, O., Urso, S., & Tomás, J. (2022). Nesting range expansion of loggerhead turtles in the Mediterranean: Phenology, spatial distribution, and conservation implications. Global Ecology and Conservation, 38, e02194. https://doi.org/10.1016/j.gecco.2022.e02194