Data from: Interactive influences of climate change and agriculture on aquatic habitat in a Pacific Northwestern watershed

Climate change and agricultural intensification are two potential stressors that may pose significant threats to aquatic habitats in the inland Pacific Northwest over the next century. Climate change may impact running water through numerous pathways, including effects on water temperature and stream flow. In certain regions of the Pacific Northwest, agricultural activities, such as crop production, may become more profitable if water projects result in more irrigation water. If so, riparian buffers in these areas may be converted into cropland, which may in turn affect aquatic habitats through increases in sediment and agrochemical runoff into streams. We used currently available downscaled temperature and hydrology data in combination with a habitat quality framework developed for Pacific salmon and trout (Oncorhynchus spp.) to predict how different levels of each stressor, alone and in combination, may impact aquatic habitats in an inland Pacific Northwest watershed dominated by high-value agriculture—the Umatilla Subbasin. We developed spatially explicit predictions for how changes in stream flow and water temperature associated with three climate change scenarios and loss of riparian buffers in two agricultural intensification scenarios may impact aquatic habitats. We also examined the cumulative effects of the interaction of extreme climate change and agricultural intensification scenarios. Our results show that all three climate change scenarios are expected to primarily impact aquatic habitat in the upper Subbasin. In contrast, agricultural intensification scenarios did not have large impacts on temperature, but are predicted to affect other water quality variables in the lower Subbasin. A moderate scenario of agricultural intensification had relatively little effect on aquatic habitat, whereas the removal of all riparian buffers in agriculturally viable areas had a substantially negative effect on sediment, embeddedness, and large woody debris in the lower Subbasin. Interactions between the most extreme climate change and agricultural intensification scenarios reflected a complementarity of effects, with climate change primarily affecting the upper Subbasin and agricultural intensification primarily impacting the lower Subbasin. This work suggests that the Umatilla Subbasin and similar watersheds will present a challenging habitat for warm water- and pollution-intolerant species in the coming century.

气候变化与农业集约化（agricultural intensification）是两大潜在胁迫因子，未来百年内或对太平洋西北地区内陆的水生栖息地构成显著威胁。气候变化可通过多种途径影响河川径流，包括对水温和径流量的影响。在太平洋西北地区的部分区域，若水利工程能提供更多灌溉用水，农业活动（如作物种植）的收益或有所提升。若出现此种情形，该区域的河岸缓冲带（riparian buffers）可能被改造为农田，进而通过泥沙与农业化学物质径流进入溪流的过程，对水生栖息地造成影响。本研究结合当前可用的降尺度气温与水文数据，以及为太平洋鲑属鱼类（Oncorhynchus spp.）开发的生境质量框架，预测了两类胁迫因子各自及联合作用下的不同强度，将如何对以高价值农业为主的太平洋西北地区内陆流域——尤马蒂拉亚流域（Umatilla Subbasin）——的水生栖息地产生影响。我们针对三种气候变化情景下的径流量与水温变化，以及两种农业集约化情景下的河岸缓冲带丧失，生成了空间显式预测（spatially explicit predictions）结果，以分析其对水生栖息地的影响。此外，我们还考察了极端气候变化与农业集约化情景交互作用下的累积效应。研究结果显示，三种气候变化情景均主要对亚流域上游的水生栖息地造成影响。与之形成对比的是，农业集约化情景并未对水温产生显著影响，但预计会影响亚流域下游的其他水质变量。适度的农业集约化情景对水生栖息地的影响相对有限，而在农业适宜区域移除全部河岸缓冲带，则会对亚流域下游的泥沙、底质嵌入度（embeddedness）及大型木质碎屑（large woody debris）产生显著负面影响。极端气候变化与农业集约化情景间的交互作用体现出效应互补性：气候变化主要影响亚流域上游，而农业集约化则主要作用于亚流域下游。本研究表明，尤马蒂拉亚流域及类似流域在未来百年内，将为不耐高温与污染的物种（warm water- and pollution-intolerant species）提供极具挑战性的栖息环境。