Wildlife Biology Program, University of Montana, Missoula, MT, USA.
Skagit River Systems Cooperative, La Conner, WA, USA.
Glob Chang Biol. 2020 Oct;26(10):5492-5508. doi: 10.1111/gcb.15281. Epub 2020 Aug 20.
A broader understanding of how landscape resistance influences climate change vulnerability for many species is needed, as is an understanding of how barriers to dispersal may impact vulnerability. Freshwater biodiversity is at particular risk, but previous studies have focused on popular cold-water fishes (e.g., salmon, trout, and char) with relatively large body sizes and mobility. Those fishes may be able to track habitat change more adeptly than less mobile species. Smaller, less mobile fishes are rarely represented in studies demonstrating effects of climate change, but depending on their thermal tolerance, they may be particularly vulnerable to environmental change. By revisiting 280 sites over a 20 year interval throughout a warming riverscape, we described changes in occupancy (i.e., site extirpation and colonization probabilities) and assessed the environmental conditions associated with those changes for four fishes spanning a range of body sizes, thermal and habitat preferences. Two larger-bodied trout species exhibited small changes in site occupancy, with bull trout experiencing a 9.2% (95% CI = 8.3%-10.1%) reduction, mostly in warmer stream reaches, and westslope cutthroat trout experiencing a nonsignificant 1% increase. The small-bodied cool water slimy sculpin was originally distributed broadly throughout the network and experienced a 48.0% (95% CI = 42.0%-54.0%) reduction in site occupancy with declines common in warmer stream reaches and areas subject to wildfire disturbances. The small-bodied comparatively warmer water longnose dace primarily occupied larger streams and increased its occurrence in the lower portions of connected tributaries during the study period. Distribution shifts for sculpin and dace were significantly constrained by barriers, which included anthropogenic water diversions, natural step-pools and cascades in steeper upstream reaches. Our results suggest that aquatic communities exhibit a range of responses to climate change, and that improving passage and fluvial connectivity will be important climate adaptation tactics for conserving aquatic biodiversity.
需要更广泛地了解景观阻力如何影响许多物种对气候变化的脆弱性，以及扩散障碍如何影响脆弱性。淡水生物多样性面临特别的风险，但以前的研究集中在体型较大、移动性较强的受欢迎的冷水鱼类（如鲑鱼、鳟鱼和鳜鱼）上。这些鱼类可能能够更熟练地追踪栖息地的变化。体型较小、移动性较弱的鱼类在展示气候变化影响的研究中很少出现，但根据它们的耐热性，它们可能特别容易受到环境变化的影响。通过在 20 年的时间里在一个变暖的河流景观中重新访问 280 个地点，我们描述了四个鱼类物种的栖息地占有率（即地点灭绝和定居概率）的变化，并评估了与这些变化相关的环境条件，这些鱼类的体型、热和栖息地偏好范围较广。两种体型较大的鳟鱼物种的栖息地占有率变化较小，虹鳟经历了 9.2%（95%置信区间为 8.3%-10.1%）的减少，主要发生在较温暖的溪流段，而西部截尾鳟经历了微不足道的 1%的增加。体型较小的冷水粘鱼原本广泛分布于整个网络，栖息地占有率减少了 48.0%（95%置信区间为 42.0%-54.0%），在较温暖的溪流段和易受野火干扰的地区下降较为常见。体型较小的温水长吻鼻鱼主要栖息在较大的溪流中，并在研究期间增加了在连接的支流下游部分的出现。粘鱼和鼻鱼的分布变化受到障碍的显著限制，这些障碍包括人为的引水、上游陡峭处的自然阶地和瀑布。我们的研究结果表明，水生群落对气候变化表现出多种反应，改善通道和河流连通性将是保护水生生物多样性的重要气候适应策略。
