Northwest Fisheries Science Center, NOAA Fisheries, 2725 Montlake Blvd E., Seattle, WA, 98112, U.S.A.
Conserv Biol. 2013 Dec;27(6):1201-11. doi: 10.1111/cobi.12168.
Significant challenges remain in the ability to estimate habitat change under the combined effects of natural variability, climate change, and human activity. We examined anticipated effects on shallow water over low-sloped beaches to these combined effects in the lower Willamette River, Oregon, an area highly altered by development. A proposal to stabilize some shoreline with large rocks (riprap) would alter shallow water areas, an important habitat for threatened Chinook salmon (Oncorhynchus tshawytscha), and would be subject to U.S. Endangered Species Act-mandated oversight. In the mainstem, subyearling Chinook salmon appear to preferentially occupy these areas, which fluctuate with river stages. We estimated effects with a geospatial model and projections of future river flows. Recent (1999-2009) median river stages during peak subyearling occupancy (April-June) maximized beach shallow water area in the lower mainstem. Upstream shallow water area was maximized at lower river stages than have occurred recently. Higher river stages in April-June, resulting from increased flows predicted for the 2080s, decreased beach shallow water area 17-32%. On the basis of projected 2080s flows, more than 15% of beach shallow water area was displaced by the riprap. Beach shallow water area lost to riprap represented up to 1.6% of the total from the mouth to 12.9 km upstream. Reductions in shallow water area could restrict salmon feeding, resting, and refuge from predators and potentially reduce opportunities for the expression of the full range of life-history strategies. Although climate change analyses provided useful information, detailed analyses are prohibitive at the project scale for the multitude of small projects reviewed annually. The benefits of our approach to resource managers include a wider geographic context for reviewing similar small projects in concert with climate change, an approach to analyze cumulative effects of similar actions, and estimation of the actions' long-term effects. Efectos Combinados del Cambio Climático y la Estabilización de Bordes de Ríos Hábitats de Aguas Poco Profundas del Salmón Chinook.
在自然变异、气候变化和人类活动的综合影响下，估计栖息地变化的能力仍然存在重大挑战。我们研究了在俄勒冈州威拉米特河下游，一个受发展高度影响的地区，这些综合影响对低坡度海滩浅水区的预期影响。一项用大石头（护堤块石）稳定部分海岸线的提案将改变浅水区，这是受威胁的奇努克鲑鱼（Oncorhynchus tshawytscha）的重要栖息地，并将受到美国濒危物种法案的监督。在干流中，亚成体奇努克鲑鱼似乎更喜欢占据这些随河流水位变化而波动的区域。我们使用地理空间模型和未来河流水流预测来估计影响。在亚成体鲑鱼最常出现的高峰期（4 月至 6 月），最近（1999-2009 年）的河流中位阶段最大限度地增加了下游干流的海滩浅水区面积。上游浅水区在比最近出现的更低的河流水位阶段最大化。由于预测到 2080 年代流量增加，4 月至 6 月的河流较高水位减少了海滩浅水区 17-32%。根据预测的 2080 年代流量，超过 15%的海滩浅水区被护堤块石取代。因护堤块石而损失的海滩浅水区面积占从河口到上游 12.9 公里的总面积的 1.6%。浅水区面积的减少可能限制鲑鱼的觅食、休息和躲避捕食者，并可能减少其充分表达生命史策略的机会。尽管气候变化分析提供了有用的信息，但在项目规模上，对每年审查的众多小型项目进行详细分析是不可行的。我们的方法为资源管理者带来的好处包括在更广泛的地理背景下审查类似的小型项目，并与气候变化相结合，提供一种分析类似行动累积影响的方法，以及估计这些行动的长期影响。
