For millions of years, female sea turtles have been coming ashore to lay their eggs on Florida beaches, an activity that takes place at night. Today, Florida's coastal areas are highly populated and artificial lighting is common on or near sea turtle nesting beaches. While this might be appealing to humans, it causes problems for nesting sea turtles and can deter them from coming ashore. The incursion of light into these once-dark environments can also disorient hatchlings, which instinctively move toward the brightest, horizon. On a naturally lit dark beach, that is over the ocean, but in populated areas, artificial lights can lure hatchlings away from the ocean, toward civilization.
Efforts initiated in the 1980's within the State of Florida's sea turtle program and among, non-profit organizations, and federal, county, and local governments resulted in the development of state and local lighting ordinances in many places where sea turtles nest. These ordinances included ways to reduce light pollution near nesting beaches through the use of certain wavelength lighting, improved light fixture design, better positioning, and the shielding of light fixtures.
Now, more than three decades later, a new study from the University of Central Florida (UCF) involving data from NOAA satellites finds that the lighting ordinances along Florida's coast seem to be working.
The Science Fair and Beyond
The study, recently published in the open access journal Remote Sensing in Ecology and Conservation, began in 2015, when Zachary Weishampel –son of UCF biology professor John Weishampel— was looking for a science fair project. His father suggested he explore how sea turtles have fared since county and local governments in Florida began adopting restrictions on coastal lighting. Zachary, who had used NASA satellite data for a previous project, agreed and the two began collecting data on artificial light intensity captured by the Defense Meteorological Satellite Program (DMSP) from 1992 to 2012. They then compared it to Florida Fish and Wildlife Conservation Commission data on nesting sea turtles for the same period.
"Publically available DMSP data have been around since 1992. This corresponds pretty closely to the sea turtle nesting surveys carried out by the Florida Fish and Wildlife Conservation Commission which began systematically monitoring nest activity along the Florida coastlines in 1989," said UCF's John Weishampel. "A couple of Australian studies by Kamrowski et al. (2012 and 2014) used DMSP data to show artificial light trends across their coastal regions which demonstrated the methodology."
The DMSP is a network of satellites that NOAA operates on behalf of the U.S. Air Force. DMSP satellites monitor a variety of weather and environmental factors, such as cloud type and height, land and surface water temperatures, water currents, ocean surface features, ice and snow. In addition, some DMSP satellites have night visual sensors with the unique capability to detect low levels of visible near-infrared radiance at night. These instruments make it possible to detect clouds illuminated by moonlight, lights from cities and towns, gas flares, volcanoes, fires, and even the Northern Lights.
Population Up, Light Levels Down
Given that Florida's population increased by more than 5 million people during this period, the researchers expected the amount of artificial light would have increased as well. However, with assistance from UCF graduate student Wan-Hwa Cheng, they found thatnighttime light levels decreased for more than two-thirds of the 368 one-kilometer (.62-mile) sections of beach they examined. Of the remaining one-third, about 14 percent showed increases in artificial light. The rest hadn't changed.
When the assessments of light were compared with the turtle nesting data, the researchers found that there were fewer turtle nests where artificial light is brightest and more where it's dark. They also concluded that, in addition to beach lighting, turtle nesting locations are also affected by light from more distant urban areas—a phenomenon known as "skyglow."
It's a success story. Florida's coastlines are getting darker, and that's a good thing not just for sea turtles but for other organisms," Weishampel said in a UCF press release about the study. "It shows we affect turtles' nesting, but at the same time we've been successful at reducing that effect."
Of course, the alteration of nesting habitat is just one of several threats impacting sea turtle populations. In the ocean, where sea turtles live the vast majority of their lives, they are at risk of getting trapped in the nets and lines of commercial fishing operations, ingesting or becoming entangled in marine debris, or being injured (or killed) by boat strikes. Further, disturbance and degradation of their habitats by coastal runoff, marina and dock construction, dredging, aquaculture, and oil and gas exploration and production are also threats to their recovery.
Satellites: A Boon to Conservation
Satellites can help biologists better understand the nature of these threats as they develop ways to minimize them. NOAA satellites have been used to track oil spills, monitor the location of commercial fishing vessels, the size and location of algal blooms, and, as part of the ARGOS Program, track the movements of sea turtles. Indeed, beyond providing data on artificial light, Weishampel said that he has also used satellite data on sea-surface temperature, land cover and land use.
"I generally use these data to show dynamics of broad-scale systems which can be related to the ecology of other organisms or to the alteration of habitat," he said.
Ultimately, satellites benefit biologists by allowing them to view the world differently, said Weishampel.
"[Satellites] extends our senses. We are able to see coarse patterns across the land or seascape, and how they change. They often use different sensors that go beyond our capabilities. As a result, we can examine habitat changes for wide-ranging species or assess how different biophysical processes, such as carbon sequestration, occur across the globe."