Mapping Polar Bear Maternal Denning Habitat in the National Petroleum Reserve–Alaska with an IfSAR Digital Terrain Model

Abstract

The National Petroleum Reserve-Alaska (NPR-A) in northeastern Alaska provides winter maternal denning habitat for polar bears (Ursus maritimus) and also has high potential for recoverable hydrocarbons. Denning polar bears exposed to human activities may abandon their dens before their young are able to survive the severity of Arctic winter weather. To ensure that wintertime petroleum activities do not threaten polar bears, managers need to know the distribution of landscape features in which maternal dens are likely to occur. Here, we present a map of potential denning habitat within the NPR-A. We used a fine-grain digital elevation model derived from Interferometric Synthetic Aperture Radar (IfSAR) to generate a map of putative denning habitat. We then tested the map's ability to identify polar bear denning habitat on the landscape. Our final map correctly identified 82% of denning habitat estimated to be within the NPR-A. Mapped denning habitat comprised 19.7 km 2 (0.1% of the study area) and was widely dispersed. Though mapping denning habitat with IfSAR data was as effective as mapping with the photogrammetric methods used for other regions of the Alaskan Arctic coastal plain, the use of GIS to analyze IfSAR data allowed greater objectivity and flexibility with less manual labor. Analytical advantages and performance equivalent to that of manual cartographic methods suggest that the use of IfSAR data to identify polar bear maternal denning habitat is a better management tool in the NPR-A and wherever such data may be available.

Modeling the spatial and temporal dynamics of land‐based polar bear denning in Alaska

“…East of the Canning River in the Arctic National Wildlife Refuge (ANWR), The Tax Cuts and Jobs Act of 2017 (Public Law 115‐97) authorized oil and gas leasing within the ANWR 1002 Area (1002). These 3 regions of existing and proposed hydrocarbon activities overlap with the distribution of most observed terrestrial polar bear dens and denning habitat in Alaska (Durner et al 2003, 2006, 2013).…”

“…The probability of land dens occurring within the 1002 region of ANWR declined throughout the study period, yet the mainland portion of the 1002 contained ample denning habitat based on topography (Durner et al 2006(Durner et al , 2013, and fall snow depth has not decreased since the 1980s (Figures S1-2). The continued availability of snowdrift den habitat helps explain how the relatively small 1002 region was able to support between 5 and 30 land dens/year.…”

“…The thick black line delineates the Southern Beaufort Sea (SBS) subpopulation boundary in both panels. A) Locations of polar bear maternal dens on sea ice and land, 1982-1999 (old) These 3 regions of existing and proposed hydrocarbon activities overlap with the distribution of most observed terrestrial polar bear dens and denning habitat in Alaska (Durner et al 2003(Durner et al , 2006(Durner et al , 2013.…”

Modelling polar bear maternity den habitat in east Svalbard

“…Dashes indicate that the given variable was unavailable for the given model set. islands with only a few metres height provide drifts for dens in large flat areas with few good alternatives (Durner et al 2001;Durner et al 2003;Durner et al 2013).…”

Evaluating the efficacy of aerial infrared surveys to detect artificial polar bear dens

“…We recommend investing in improving detection technology, thermal signature recognition/discrimination, and survey methodology, but we also recognize that there is an immediate need to increase the likelihood of detecting polar bear dens. Known den locations (Durner et al 2020) and den habitat distribution (e.g., Durner et al 2001Durner et al , 2006Durner et al , 2013 are used to develop industry AIR survey transects, but this information could be further leveraged. For example, the SnowDens-3D model that predicts snowdrift location and depth in polar bear den habitat (Liston et al 2016) could be incorporated into AIR surveys to inform the likelihood of den occurrence by concentrating on areas with sufficient snowdrifts.…”