Department of Civil and Environmental Engineering, Faculty of Engineering, University of Miyazaki, Gakuen Kibanadai-nishi 1-1, Miyazaki 889-2192, Japan.
Fluid Dynamics Sector, Central Research Institute of Electric Power Industry, Postal address: 1646 Abiko, Abiko-shi, Chiba 270-1194, Japan.
Sci Total Environ. 2018 Nov 15;642:610-618. doi: 10.1016/j.scitotenv.2018.06.109. Epub 2018 Jun 14.
Climate change places considerable stress on riverine ecosystems by altering flow regimes and increasing water temperature. This study evaluated how water temperature increases under climate change scenarios will affect stream invertebrates in pristine headwater streams. The studied headwater-stream sites were distributed within a temperate catchment of Japan and had similar hydraulic-geographical conditions, but were subject to varying temperature conditions due to altitudinal differences (100 to 850 m). We adopted eight general circulation models (GCMs) to project air temperature under conservative (RCP2.6), intermediate (RCP4.5), and extreme climate scenarios (RCP8.5) during the near (2031-2050) and far (2081-2100) future. Using the water temperature of headwater streams computed by a distributed hydrological-thermal model as a predictor variable, we projected the population density of stream invertebrates in the future scenarios based on generalized linear models. The mean decrease in the temporally averaged population density of Plecoptera was 61.3% among the GCMs, even under RCP2.6 in the near future, whereas density deteriorated even further (90.7%) under RCP8.5 in the far future. Trichoptera density was also projected to greatly deteriorate under RCP8.5 in the far future. We defined taxa that exhibited temperature-sensitive declines under climate change as cold stenotherms and found that most Plecoptera taxa were cold stenotherms in comparison to other orders. Specifically, the taxonomic families that only distribute in Palearctic realm (e.g., Megarcys ochracea and Scopura longa) were selectively assigned, suggesting that Plecoptera family with its restricted distribution in the Palearctic might be a sensitive indicator of climate change. Plecoptera and Trichoptera populations in the headwaters are expected/anticipated to decrease over the considerable geographical range of the catchment, even under the RCP2.6 in the near future. Given headwater invertebrates play important roles in streams, such as contributing to watershed productivity, our results provide useful information for managing streams at the catchment-level.
气候变化通过改变水流模式和提高水温，给河流生态系统带来了巨大的压力。本研究评估了在气候变化情景下，水温升高将如何影响原始源头溪流中的溪流无脊椎动物。所研究的源头溪流站点分布在日本一个温带流域内，具有相似的水力地理条件，但由于海拔差异（100 至 850 米），水温条件也有所不同。我们采用了八个通用环流模型（GCMs），以在保守情景（RCP2.6）、中间情景（RCP4.5）和极端情景（RCP8.5）下预测近（2031-2050 年）和远（2081-2100 年）未来的空气温度。使用分布式水文热模型计算的源头溪流水温作为预测变量，我们基于广义线性模型预测了未来情景中溪流无脊椎动物的种群密度。即使在近未来的 RCP2.6 情景下，GCMs 预测的蜉蝣类的时空平均种群密度平均减少了 61.3%，而在远未来的 RCP8.5 情景下，密度恶化甚至更大（90.7%）。预测 Trichoptera 的密度也将在远未来的 RCP8.5 情景下大幅恶化。我们将在气候变化下表现出对温度敏感下降的分类群定义为冷狭温动物，并发现与其他目相比，大多数蜉蝣类属于冷狭温动物。具体而言，仅分布在古北区（如 Megarcys ochracea 和 Scopura longa）的分类科被选择性地分配，这表明蜉蝣科在古北区的有限分布可能是气候变化的敏感指标。即使在近未来的 RCP2.6 情景下，集水区相当大的地理范围内的源头溪流的蜉蝣目和 Trichoptera 种群预计/预期将会减少。鉴于源头溪流无脊椎动物在溪流中发挥着重要作用，例如为流域生产力做出贡献，我们的研究结果为集水区层面的溪流管理提供了有用的信息。
