May 1, 2014 | 7
A sea turtle’s life begins in darkness. After about 60 days of incubation inside their eggs, turtle hatchlings use a temporary tooth called a caruncle to break out of their shells. That’s just step one. At this point, they are still buried in nests about 50 centimeters below the beach surface. As dozens of baby turtles emerge from their eggs, they then begin to force themselves upward through the sand. Working together, they climb and scrape and push. As they get closer to the surface, they begin to feel the warmth of the sun. Instinctively, they know that the sun’s rays pose the first danger of their young lives. If they get too much sun before they make it to the ocean, the hatchlings could quickly become dehydrated and die. But when they’re ready to emerge—usually during the cool night or a storm—they emerge all at once, take a look around, and head toward the water.
That’s where modern society throws them a curve. Under natural conditions, the turtle hatchlings would be faced with two choices: the dark slopes of dunes and vegetation behind them and the gentle light of the ocean horizon ahead of them. Sea turtle hatchlings instinctively head toward the light, sensing the moon and stars reflected on the water. But today the brightest light comes not from the ocean but from the hotels, condominiums, restaurants and homes that crowd most beaches. These man-made lights draw the hatchlings like moths to a flame. They quickly grow disorientated, lose their bearings and either die of dehydration, get run over by cars or are eaten by birds and other predators.
In Florida tens of thousands of sea turtle hatchlings die every year as they walk toward civilization and away from the ocean waters they need to survive. The state is home to 90 percent of the sea turtle nesting in the U.S., and the loss of so many hatchlings poses a major risk to the long-term survival of three endangered species: green (Chelonia mydas), loggerhead (Caretta caretta) and Kemp’s ridley (Lepidochelys kempii) turtles. (Two other sea turtle species also nest in Florida in lower numbers.)
But just as light creates a danger for the turtles, it can also be the solution. New LED lights operating at a specific wavelengths and lower levels of visible light (lumens) have been shown to dramatically reduce sea turtle hatchling disorientations. In fact, David Godfrey, executive director of the Sea Turtle Conservancy (STC), reports hatchling disorientations on many properties that have switched to these new LED lights have fallen from hundreds every year to zero. “It’s a long-term project to replace old lights,” he says, “but it is working.”
The new lights, according to the conservancy’s sea turtle specialist Karen Shudes, operate at wavelengths that do not attract sea turtles. “The optimal sea-turtle-friendly lighting is 580 nanometers or longer,” she says. That wavelength is around the yellow/orange part of the spectrum, with red following at about 700 nanometers. LED lights fitting these parameters are available in many stores in Florida, where they are marketed as “turtle safe” and have been certified as wildlife friendly by the Florida Fish and Wildlife Conservation Commission. The lights also have other benefits: They use 70 percent less energy than incandescent bulbs and provide a more pleasing light, which the STC says can actually enhance people’s safety by not overwhelming human night vision with glaring spotlights.
People first tried using yellow or red lights 30 years ago to try to stop turtle disorientations, but Godfrey says those early lights didn’t actually do the trick. “Even though a bud or sodium light might look yellow to you or me,” he says, “if you looked at it through a spectroscope, you would see the full spectrum of light. It may peak in the yellow region but there’s plenty of light throughout the spectrum. So those lights were still attracting turtles because they were sensitive to those different wavelengths.”
Beyond the LED bulbs themselves, new fixtures that point light toward the ground and are angled away from beaches also help reduce turtle disorientations. “There are several rules of turtle lighting,” Shudes says. “Keep the light as low to the ground as possible, keep the lumens as low as possible, keep the light shielded and keep the wavelength long.”
The STC itself has completed more than 80 major lighting retrofit projects on local hotels, resorts, condo complexes and a few homes. A lot of the money to fund these retrofits comes out of criminal penalties from the 2010 Deepwater Horizon oil spill, which killed or otherwise affected an estimated 100,000 sea turtles. The first two years of the STC’s retrofit efforts were financed by the Recovered Oil Fund for Wildlife (which itself was created with money from Deepwater owner British Petroleum); the organization just received additional funding from the similar Gulf Environmental Benefit Fund, both of which are administered by the National Fish and Wildlife Foundation.
This restitution money, Godfrey says, “has allowed us to actually work with private property owners to go ahead and convert their lights, to work with them, to supplement the money they’re spending. We match money they put in. In some cases where the problem is particularly heinous and the property owners just don’t have the money to fix the problem, we can actually go in and do it for them. That funding mechanism, which has been made available following the spill, has allowed a lot of major progress on this issue.” The changes aren’t voluntary—use of turtle-friendly lights during nesting season has been mandated by state and county ordinances.
The work to date has definitely had a positive result. Not only have baby turtle disorientations diminished or been completely eliminated in many of the retrofitted areas, turtles have even started nesting at sites they avoided in the past.
Despite the progress, many areas still have too many lights, either shining directly on the beach or emanating overall from the cities adjacent to beachfront properties. Meanwhile, the effects of the BP spill on sea turtle populations may still be felt for years to come. “Sea turtles take as long as 40 years to reach sexual maturity, so when you lose an adult it’s a real assault on the population,” Godfrey says.
That’s why efforts to save hatchlings long enough to get into the ocean matter. “We don’t have to handle the turtles to save them,” Godfrey says. “We’re restoring their habitat and they do the rest.”
Main photo: A leatherback turtle hatchling via the Florida Fish and Wildlife (uncredited). Green turtle on Florida beach © Ralph Pace, courtesy of Sea Turtle Conservancy and lighting photos courtesy of Sea Turtle Conservancy
Related on Scientific American:
Previously in Extinction Countdown:
Give a 1 year subscription as low as $14.99X