Glacier retreat creating new Pacific salmon habitat in western North America

Glacier retreat poses risks and benefits for species of cultural and economic importance. One example is Pacific salmon (<em>Oncorhynchus</em> spp.), which support subsistence harvests, and commercial and recreational fisheries worth billions of dollars annually. Although decreases in summer streamflow and warming freshwater is reducing Pacific salmon habitat in parts of their range, glacier retreat is creating new streams and lakes that salmon can colonize. However, potential gains in future salmon habitat associated with glacier loss have yet to be quantified across the range of Pacific salmon. Here we project future gains in Pacific salmon freshwater habitat by linking a model of glacier mass change for 315 glaciers, forced by five different Global Climate Models, with a simple model of salmon stream habitat potential throughout the Pacific Mountain ranges of western North America. We project that by the year 2100 glacier retreat will create 6,146 (+1,619) km of new streams accessible for colonization by Pacific salmon, of which 1,930 (+569) km have the potential to be used for spawning and juvenile rearing, representing 0 to 27% gains within the 18 sub-regions we studied. These findings can inform proactive management and conservation of Pacific salmon in this era of rapid climate change.冰川消退对兼具文化与经济重要性的物种而言，兼具风险与收益。以太平洋鲑鱼（Pacific salmon，<em>Oncorhynchus</em> spp.）为例，其支撑的生计捕捞、商业与休闲渔业年产值高达数十亿美元。尽管夏季河川径流量缩减与淡水水温升高，正不断压缩部分分布区内的太平洋鲑鱼栖息地，但冰川消退正形成全新的溪流与湖泊，可供鲑鱼拓殖。不过，目前学界尚未针对太平洋鲑鱼的整个分布范围，量化冰川消退所带来的未来鲑鱼栖息地潜在增益。本研究借助由5种不同全球气候模型（Global Climate Models）驱动的315处冰川质量变化模型，结合北美西部太平洋山脉全域内的鲑鱼溪流栖息地潜力简化模型，对太平洋鲑鱼淡水栖息地的未来增益进行预测。我们预测，至2100年，冰川消退将形成6146（±1619）千米的适宜太平洋鲑鱼拓殖的新生溪流，其中1930（±569）千米具备作为产卵场与幼鱼育幼栖息地的潜力；在本次研究涵盖的18个亚区域内，该栖息地增益幅度可达0至27%。上述研究结果可为快速气候变化时代下太平洋鲑鱼的主动管理与保护工作提供科学参考。