No more beach time for sea turtles?
Compared with most sea turtles, green turtles (Chelonia mydas) are beach bums. Whereas other species spend virtually their entire lives at sea—coming ashore for only a few hours to nest—green turtles can be spotted throughout the year on sandy Pacific beaches. But fast-forward a few decades, and these sightings might be rarer. In an attempt to understand what makes green turtles catch their rays on the sand, scientists tracked the number of turtles sunning themselves on one Hawaii beach. Every day for 6 years, volunteers there tallied the turtles. The animals, researchers report online today in Biology Letters, tend to come ashore when the sea surface temperatures drop below 23°C. Today, this occurs during the winter months in Hawaii, the Galápagos Islands, and some Australia beaches within the sea turtles’ range. But the sea surface temperatures in these areas have been rising by about 0.04°C per year. If this rate continues, by 2039 Hawaii’s water will be warm enough that the turtles won’t get chilly enough in the winter to bask on the sand. By 2100, the researchers hypothesize, green turtles might not be seen basking on any Pacific beaches, instead keeping warm enough in the water. Because they still haven’t cleared up the biological importance of warming on land for green turtles, researchers don’t yet know whether this change could negatively impact the turtle populations.