Beavers are starting to colonize low arctic tundra regions in Alaska and Canada, which has implications for surface water changes and ice-rich permafrost degradation. In this study, we assessed the spatial and temporal dynamics of beaver dam building in relation to surface water dynamics and thermokarst landforms using sub-meter resolution satellite imagery acquired between 2002 and 2019 for two areas in northwestern Alaska. In a 100 km2 study area near Kotzebue, the number of dams increased markedly from 2 to 98 between 2002 and 2019. In a 430 km2 study area encompassing the entire northern Baldwin Peninsula, the number of dams increased from 94 to 409 between 2010 and 2019, indicating a regional trend. Correlating data on beaver dam numbers with surface water area mapped for 12 individual years between 2002 and 2019 for the Kotzebue study area showed a significant positive correlation (R2 = 0.61; p < .003). Beaver-influenced waterbodies accounted for two-thirds of the 8.3 % increase in total surface water area in the Kotzebue study area during the 17-year period. Beavers specifically targeted thermokarst landforms in their dam building activities. Flooding of drained thermokarst lake basins accounted for 68 % of beaver-influenced surface water increases, damming of lake outlets accounted for 26 %, and damming of beaded streams accounted for 6 %. Surface water increases resulting from beaver dam building likely exacerbated permafrost degradation in the region, but dam failure also factored into the drainage of several thermokarst lakes in the northern Baldwin Peninsula study region, which could promote local permafrost aggradation in freshly exposed lake sediments. Our findings highlight that beaver-driven ecosystem engineering must be carefully considered when accounting for changes occurring in some permafrost regions, and in particular, regional surface water dynamics in low Arctic and Boreal landscapes.

中文翻译：

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海狸水坝的增加控制了阿拉斯加西北部鲍德温半岛北极苔原地区的地表水和热岩溶动态

海狸开始在阿拉斯加和加拿大的低北极苔原地区定居，这对地表水变化和富含冰的永久冻土退化产生了影响。在这项研究中，我们使用 2002 年至 2019 年期间在阿拉斯加西北部的两个地区获取的亚米分辨率卫星图像，评估了海狸坝建设的时空动态与地表水动力学和热岩溶地貌的关系。在 Kotzebue 附近的 100 平方公里研究区，2002 年至 2019 年间，大坝数量从 2 座显着增加到 98 座。在涵盖整个鲍德温半岛北部的 430 平方公里研究区中，2010 年至 2019 年间，大坝数量从 94 座增加到 409 座，显示区域趋势。将海狸坝数量与 2002 年至 2019 年 Kotzebue 研究区的 12 个单独年份的地表水域面积相关的数据显示出显着的正相关（R2 = 0.61；p < .003）。在 17 年期间 Kotzebue 研究区地表水域总面积增加 8.3% 中，受海狸影响的水体占三分之二。海狸在他们的大坝建设活动中专门针对热岩溶地貌。在受海狸影响的地表水增加中，排干热岩溶湖盆的洪水占 68%，湖泊出水口筑坝占 26%，珠状溪流筑坝占 6%。海狸水坝建设导致地表水增加可能加剧了该地区的永久冻土退化，但大坝倒塌也是鲍德温半岛北部研究区几个热岩溶湖泊排水的一个因素，这可能会促进新暴露的湖泊沉积物中局部永久冻土的聚集。我们的研究结果强调，在解释一些永久冻土地区发生的变化时，必须仔细考虑海狸驱动的生态系统工程，特别是北极和北方低地景观中的区域地表水动态。