DataSheet_1_Relating polar bears killed, human presence, and ice conditions in Svalbard 1987–2019.pdf

Conflicts between humans and polar bears have been predicted to increase as polar bear prime habitat, sea ice, is decreasing. In Svalbard, a strict protection and control schemes have secured near complete records of bears killed and found dead since 1987. We analyzed the trend in the number of kills and related this to human visitation to the archipelago. We found a slight decrease in the number of kills in the period 1987-2019, and a decrease in per capita number of kills when monthly kills were compared to the monthly number of visitors disembarking in the main settlement. We then used a discrete choice resource selection model to assess whether polar bear kill events are related to attributes of the kill sites and environmental conditions at the time. We divided Svalbard in four sectors, North, East, South, and West, and monthly average ice cover was calculated in 25-km rings around Svalbard, rings that were further delineated by the four sectors. We found that the odds of a kill was greater along the shoreline, and that the odds would be reduced by 50% when moving only 900 m from the shoreline when all sectors were included. Distance from other covariates like settlements, trapper’s cabins, and landing sites for tourists did for the most part not have a significant impact on the odds of a kill. Sectorwise, ice cover had no significant impact on the odds for a kill. The decreasing trend in kills of polar bears might partly be explained by the success of strict protection and management regimes of Svalbard wilderness.

随着北极熊核心栖息地海冰的缩减，人类与北极熊之间的冲突预计将愈发频繁。在斯瓦尔巴群岛（Svalbard），自1987年起，严格的保护与管控机制已实现了对被捕杀及发现死亡的北极熊的近乎完整记录。本研究分析了北极熊被杀数量的变化趋势，并将其与该群岛的人类到访情况进行关联分析。我们发现，1987年至2019年间，北极熊被杀总数略有下降；若将月度被杀数与主要定居点的月度登岸游客数进行对比，则单位游客对应的北极熊被杀数亦呈下降趋势。随后，本研究采用离散选择资源选择模型（discrete choice resource selection model），评估北极熊被杀事件是否与被杀地点的属性及事发时的环境条件存在关联。我们将斯瓦尔巴群岛划分为北、东、南、西四个区域，并围绕群岛以25公里为间隔绘制环形缓冲区，随后依据上述四个区域对缓冲区进行进一步划分，同时计算各区域内的月度平均海冰覆盖度。研究结果显示，北极熊被杀事件发生的几率在海岸线沿线更高；当纳入所有区域的数据时，每远离海岸线900米，该发生几率便会降低50%。其余协变量——如定居点、捕熊者小屋及游客登岸点——与被杀地点的距离，在绝大多数情况下对被杀事件的发生几率并无显著影响。分区域来看，海冰覆盖度对北极熊被杀事件的发生几率并无显著影响。北极熊被杀数的下降趋势，部分可归因于斯瓦尔巴群岛荒野地区严格的保护与管理机制所取得的成效。