As climate change drives sea levels to rise around the globe, scientists are warning that it could have a devastating effect on turtle populations. In the new research, published in the journal Royal Society Open Science, scientists found that the survival rate of endangered green sea turtle eggs dropped by 30 percent if the eggs were immersed in water for just six hours. This discovery raises concerns about the dwindling birth rate on Raine Island, near the Great Barrier Reef, where 100,000 female green sea turtles lay their eggs each summer.
Many terrestrial species are at risk from sea level rise, as seawater permanently alters the coastal landscape and destroys habitats, but for sea turtles, the treat of rising sea levels is closer and even more present. Turtles lay their eggs close to the high water line in coastal areas, which means that unpredictable changes in the tide can leave eggs submerged in salt water. If this happens, the eggs are unable to receive oxygen through the sand and soil, and can suffer hypoxia as a result, suffocating before they have even hatched.
At the Raine Island habitat in Australia, on the fringes of the Great Barrier Reef, it seems likely that this phenomenon is already causing a decline in the birth rate of endangered green sea turtles. In the remote area, around 100,000 female green sea turtles vie for prime nesting space every summer, sometimes returning to lay eggs four or five times in a single season. Yet in other turtle populations 90 percent of eggs are producing live turtles; at Raine Island that figure has dropped to just 10 percent.
So, scientists working with the North Queensland Controlled Environment Facility at James Cook University conducted a series of lab experiments using green sea turtle eggs. What they found was that control eggs, kept in optimal natural conditions hatched at a rate of 45 percent, while eggs that were inundated with seawater for a period of six hours hatched at a rate of 30 percent of the control eggs results.
The fact that only 45 percent of the eggs were viable is of itself a concern, and the scientists note in their report that this may be a result of a “range of interrelated factors” during embryonic development, including “the health of mother turtles… contaminants transferred from mothers to eggs… and/or high levels of microbes present in the soil.” But with just 10 percent of eggs hatching on Raine Island, it’s safe to believe that sea level rise is already causing the decline of this endangered animal population.