As world temperatures rise due to global warming, many animals are being affected, both positively and negatively. The publication Nature Climate Change is publishing research on Monday that states that the population of sea turtles will begin turning its numbers to have a greater proportion of females with the emergence of a warmer climate.
The reason for this phenomenon is that for many reptilian species, the sex of offspring is directly affected by the temperature at which eggs are incubated. For sea turtles, the temperature at which more female offspring are produced than male is 29 degrees Celsius, or about 84 degrees fahrenheit. After 30.5 degrees is reached, all offspring become female. This has been evidenced by the study of differently colored beaches and their respective rates of male and female offspring. Beaches with darker sand, which naturally hold more heat from the sun due to their darker pigmentation, produce more than 93 percent female offspring, whereas beaches with lighter sand produce just over 70 percent females.
An increase in the female population comes about, the short-term effects will be an increase in population growth. As male sea turtles reproduce more frequently than females do, a greater amount of females in the population means that there is more potential for children. This would benefit turtles in the short-term future, as population rates have been decreasing. One species in particular, the Green turtles of the Caribbean, will have greater benefit from a population increase, as the current population is less than 1 percent of what it was originally.
In the short-term, this will allow sea turtles to replenish their numbers, which have been dramatically reduced due to poaching and unrelated fishing operations. Though turtles are legally protected against hunting, the shells, eggs, and other parts of turtles continue to be sold illegally.
A concern raised by scientists regarding this possibility is that, if temperatures reach 30.5 degrees, the lack of males being born in the sea turtle population would lead to extinction. Graeme Hays, one of the authors of the report, stated while a warmer climate will provide a short-term population increase will provide some breathing room, the long-term results with sea turtles turning female will be more serious. It is estimated that populations of the creatures will not become dangerously low within the next 150 years, as populations are expected to increase due to an increasing number of females before beginning to drop.
Additional concerns involve the other effects of global warming that sea turtles will face. Extreme weather events, such as storm surges, are predicted to increase as climate change continues, which can disrupt nesting areas, or even destroy them in more severe cases. Higher temperatures in the ocean could lead to lower growth of sea grasses, which would threaten the food supply of sea turtles as well.
Rising sea levels will reduce the area of beaches that are above water, which means that the number of available places for turtles to lay their eggs decreases as sea levels continue to rise. Ocean currents could also be affected by global warming, which would alter the migratory patterns of turtles, and could lead hatchlings to dangerous areas of the sea.
If turtle populations continue to gradually turnout more female with the Earth’s transition into a warmer climate, the potential exists for a short-term benefit to the population. However, the long-term threat of extinction and other detrimental effects from global warming could outweigh the short-term benefit that sea turtles will experience.
By Joseph Chisarick