Rolf-Ole Rydeng Jenssen envisioned using his drone-mounted radar system to measure snowfall or forecast avalanches, once he perfected it to be able to penetrate multiple layers of snow. In subarctic Tromsø, Norway, where Jenssen works as an engineer at the multidisciplinary Norwegian Research Center (NORCE), both applications would be useful. However, one January evening, a team of scientists contacted NORCE to inquire about using the flying radar for a completely different purpose: locating polar bears that might be hiding.
In early winter, pregnant polar bears excavate holes in the snow, crawl inside, and allow new snow to cover the entrance. The bears give birth inside, protected from the harsh Arctic weather by the snow that covers them and their newborn cubs. Experts on polar bears are concerned that these creatures might be too skilled at hiding. For this reason, Jenssen received a call from scientists at Polar Bears International (PBI), a research and conservation organization. Since then, PBI and other engineers have been working together to develop more efficient methods for locating polar bear dens during aerial surveys before people trip over them and unintentionally destroy them.
In Alaska’s polar bear habitats, oil and gas companies move rigs and other equipment throughout the winter. According to Susannah Woodruff, a polar bear researcher with the U.S. Fish and Wildlife Service, “over the past two years we’ve had four dens that we know of that were disturbed in the oil fields—all dens that were previously unknown before the bears just popped out.” The possibility of den disruptions rises with increased oil and gas exploration in the Arctic, increasing the risk of harm to cubs who are more susceptible. Furthermore, these young are extremely valuable for a species that is in danger of extinction, like polar bears.
Oil and gas companies are currently required by U.S. government policies to search their sites for bear dens to avoid disturbing them. However, the device that businesses usually use for this—known as a forward-looking infrared, or FLIR, system—detects an animal’s body heat through the snow and is limited to certain operating conditions. A polar bear’s heat signal is diminished by warm weather, and it is obscured by deep or blowing snow. Furthermore, using FLIR from an airplane is a bit like attempting to scan the landscape with a smartphone camera. Users will inevitably overlook patches.
“When we looked back at how management agencies and industry were doing using this tool, the answer was ‘not that great,’” says Geoff York, PBI’s senior director of research and policy. A 2020 study co-authored by York found that FLIR failed to spot 55 percent of polar bear dens. Part of the problem is that the best weather windows for FLIR—which works better during particularly long cold periods—are now fewer and farther between because of climate change. And even under the best conditions, FLIR missed some of its targets. “Ultimately, we need to find some method that’s going to do a better job at detecting dens,” Woodruff says.
York and two colleagues came to the same conclusion while working on the freezing tundra several years ago. Frustrated with how the FLIR’s inaccuracy impacted their research, the trio started brainstorming. Radar eventually emerged as a feasible option because it works well in the conditions under which FLIR struggles. “They’re on the right track in terms of finding something that could maybe be used more frequently and isn’t weather-dependent,” says Woodruff, who isn’t involved in the radar work.
The concept behind using radar to detect polar bears is simple. The radar device is attached to a plane or drone and emits electromagnetic waves as it flies over the tundra. When the waves hit the ground, some reflect back to the radar device, and some penetrate deeper. The time it takes waves to bounce back indicates how far away a surface is. And the quantity of reflected waves differs for different types of surfaces, such as rocks, dirt, snow or water. A polar bear—which is essentially a container of water—will appear as an anomaly suspended in the snow.
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