Climate Change Reshapes Loggerhead Turtle Reproduction: Earlier Nesting, Fewer Eggs
A 17-year study of loggerhead sea turtles nesting in Cabo Verde indicates that warming oceans are leading to earlier nesting within this significant population. Concurrently, declining ocean productivity is linked to reduced frequency of female reproduction and fewer eggs laid. This research, from Queen Mary University of London and NGO Associação Projeto Biodiversidade, suggests that climate change impacts sea turtle reproduction through multiple, interacting pathways. The findings were published in the journal Animals.
Dual Impact: Timing and Productivity
Fitra Nugraha, the study's lead author, noted the complex adjustments turtles are making.
Turtles are adjusting nesting times to warmer temperatures, showing flexibility. However, the less productive Atlantic Ocean feeding grounds are diminishing their reproductive output.
Researchers found that warmer sea surface temperatures cause turtles to nest earlier and shorten the interval between successive nests, likely due to accelerated egg development. Conversely, as ocean productivity declines in their West African feeding grounds, females are now taking longer breaks between breeding seasons. Over the 17-year period, renesting intervals increased from approximately two years to four years. Upon returning, these females lay fewer clutches and fewer eggs per nest.
The "Capital Breeder" Challenge
Kirsten Fairweather, co-lead author, highlighted the nuanced reality revealed by the study.
While beach observations might suggest conservation success, long-term monitoring reveals a more complex picture where turtles expend more effort for less return.
Sea turtles are "capital breeders," meaning they rely on energy stored during feeding years to fuel reproduction. The study demonstrates a strong link between declining ocean productivity, measured by satellite estimates of chlorophyll, and longer remigration intervals, smaller clutches, and fewer nesting events. This indicates that climate change affects turtles through multiple mechanisms: warming alters timing, while changes in marine food webs reduce reproductive capacity.
Broader Conservation Strategies Needed
Christophe Eizaguirre, senior author, emphasized that temperature alone does not provide the complete story.
Temperature alone does not provide the complete story. He highlighted the importance of protecting sea turtles not only on nesting beaches but also in their feeding grounds, as conditions thousands of kilometers away directly influence egg production.
Cabo Verde hosts tens of thousands of nesting loggerhead females annually, making its population globally important. The study underlines the value of long-term monitoring efforts in detecting subtle biological changes. For conservationists, the message is clear: protecting nesting beaches remains essential but is no longer sufficient.
Fairweather concluded that safeguarding sea turtles in a warming world requires strategies extending beyond the shoreline.
Safeguarding sea turtles in a warming world requires strategies extending beyond the shoreline, including protecting feeding habitats, reducing pressures on marine ecosystems, and recognizing that climate change can undermine reproduction even in seemingly thriving populations.
The study suggests that the future of sea turtles will depend on their ability to adapt and on how quickly conservation strategies can adapt in response to warming oceans and shifting productivity.