Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, 80523, USA.
Department of Biology, Lamar University, Beaumont, TX, 77710, USA.
Glob Chang Biol. 2017 Jan;23(1):77-93. doi: 10.1111/gcb.13437. Epub 2016 Aug 26.
Shifts in biodiversity and ecological processes in stream ecosystems in response to rapid climate change will depend on how numerically and functionally dominant aquatic insect species respond to changes in stream temperature and hydrology. Across 253 minimally perturbed streams in eight ecoregions in the western USA, we modeled the distribution of 88 individual insect taxa in relation to existing combinations of maximum summer temperature, mean annual streamflow, and their interaction. We used a heat map approach along with downscaled general circulation model (GCM) projections of warming and streamflow change to estimate site-specific extirpation likelihood for each taxon, allowing estimation of whole-community change in streams across these ecoregions. Conservative climate change projections indicate a 30-40% loss of taxa in warmer, drier ecoregions and 10-20% loss in cooler, wetter ecoregions where taxa are relatively buffered from projected warming and hydrologic change. Differential vulnerability of taxa with key functional foraging roles in processing basal resources suggests that climate change has the potential to modify stream trophic structure and function (e.g., alter rates of detrital decomposition and algal consumption), particularly in warmer and drier ecoregions. We show that streamflow change is equally as important as warming in projected risk to stream community composition and that the relative threat posed by these two fundamental drivers varies across ecoregions according to projected gradients of temperature and hydrologic change. Results also suggest that direct human modification of streams through actions such as water abstraction is likely to further exacerbate loss of taxa and ecosystem alteration, especially in drying climates. Management actions to mitigate climate change impacts on stream ecosystems or to proactively adapt to them will require regional calibration, due to geographic variation in insect sensitivity and in exposure to projected thermal warming and hydrologic change.
生物多样性和生态过程在溪流生态系统中的变化对快速气候变化的响应将取决于水生昆虫物种的数量和功能优势如何对溪流温度和水文学变化做出响应。在 8 个美国西部生态区的 253 条最小干扰溪流中，我们建立了 88 个昆虫分类单元的分布模型，这些模型与最大夏季温度、年平均流量及其相互作用的现有组合有关。我们使用热图方法和气候变暖及溪流流量变化的气候模式预测数据，对每个分类单元进行特定地点的灭绝可能性估算，从而可以估算这些生态区中整个溪流社区的变化。保守的气候变化预测表明，在较温暖、较干燥的生态区，有 30-40%的分类单元可能灭绝，而在较凉爽、较湿润的生态区，由于分类单元相对免受预测的变暖和水文变化的影响，有 10-20%的分类单元可能灭绝。具有关键功能觅食作用的分类单元的差异脆弱性表明，气候变化有可能改变溪流的营养结构和功能（例如，改变碎屑分解和藻类消耗的速度），尤其是在较温暖和较干燥的生态区。我们表明，在预测对溪流群落组成的风险方面，流量变化与变暖同样重要，而且这两个基本驱动因素的相对威胁因预测的温度和水文变化梯度而在生态区之间有所不同。研究结果还表明，通过诸如水资源抽取等直接人为改变溪流的方式可能会进一步加剧分类单元的丧失和生态系统的改变，尤其是在干燥气候条件下。为了减轻气候变化对溪流生态系统的影响或主动适应这些变化，需要进行区域校准，这是因为昆虫对温度变化和暴露于预测的水文变化的敏感性以及受到的影响在地理上存在差异。
