Climate change is further imperiling loggerhead turtles that nest on Florida beaches, according to a new study by British researchers. The study warns that predicted temperature increases could decimate male North American loggerhead populations, with global ramifications for the species.
The researchers analyzed 26 years of loggerhead turtle nesting and climate data and compared the findings with models for future temperatures.
Temperature during plays a major role in the health and sex of baby turtles, with warmer temperatures during incubation producing females and cooler conditions producing males.
An increase of just one degree Celsius could completely eliminate the birth of male turtles from some beaches, the research team said, and a rise of three degrees Celsius would lead to extreme levels of infant mortality and declines in nesting beaches across the United States.
Loggerheads are considered endangered by The World Conservation Union and protected internationally by the Convention on International Trade in Endangered Species. (Photo courtesy FWS)
"We are stunned by these results and what they could mean for the species in the future," said Dr Brendan Godley of the University of Exeter's School of Biosciences. "In particular, we are concerned that populations that are already predominantly female could become 100 percent female if temperatures increase by just one degree. This is a major issue for nesting populations further south, in Florida, for example, where males are already in short supply."
In Florida, which accounts for more than 90 percent of loggerhead nesting in the United States, 90 percent of hatchlings are female. By contrast, in North Carolina, 42 percent are male. Scientists believe some of these males currently travel south, bolstering southern populations, but fear there are not enough male turtles to overcome a further shortage in Florida beaches.
Conservation efforts for the species, listed as threatened on the U.S. Endangered Species Act, should focus on protecting northern breeding grounds, the researchers said.
"In the face of climate change, it's essential that we prioritize the protection of sites that produce males not only for local breeding success, but to help support potentially vulnerable populations further south," Godley said.
The study is "an important step in identifying essential thermal habitat for marine turtles," said study co-author Dr. Matthew Godfrey, of the North Carolina Wildlife Resources Commission. "It highlights the need to establish measures to specifically protect male-producing beaches."
Published in the journal "Global Change Biology," the research was conducted in partnership with the Bald Head Island Conservancy and the North Carolina Wildlife Resources.
The study adds to growing concern about the future of loggerhead turtles, which primarily nest on beaches in Oman and Florida and take 20 to 30 years to reach maturity.
Last year scientists found continued evidence of decline on Florida beaches, where nest counts have slumped 22.3 percent from 1989 to 2005.
That report suggested that loggerheads are dying before they reach the nesting beaches - drowning in fishing trawls or taken as bycatch by the long line commercial fishing industry in the open Atlantic Ocean.
Loggerheads can weigh up to 400 pounds and are among the world's largest marine turtles. (Photo courtesy WWF-Canon/Meg Gawler)
Longline fishing is a major threat to all marine turtles, as is habitat loss and the poaching of turtle eggs, which some cultures regard as a delicacy.
But there are some encouraging signs regarding the species, particularly in South Africa. Conservationists say loggerhead nestings have reached record levels along the South African coastline, with more than 2,000 nestings found over the 2005-2006 season.
"This is the highest number recorded in 43 years," said Richard Penn Sawers, head of the WWF/Green Trust Turtle Monitoring and Community Development Project.
The conservation group contends that a major factor contributing to the stability of South Africa's marine turtle populations is that they breed almost entirely within the Greater St Lucia Wetland Park, which is a designated marine protected area and World Heritage site.