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PNAS:气候变化与山地溪流的生物多样性

 


科研人员报告说,山地溪流可能保护原产物种不受气候变化伤害,这与此前预测山地环境出现广泛灭绝的研究形成了对比。原产于冷水中的水生物种被认为特别可能面临气候变化带来的风险,但是此前对这些物种的预测依赖于稀少的数据集合,以及关于气温与水温之间关系的未经检验的假设。Daniel Isaak及其同事使用来自超过1.6万个监测站点的温度测量数据,估计了美国西北部一个22.2万公里的河流与溪流网络的历史变暖趋势。在1968年到2011年间,当每10年气温平均变暖0.21摄氏度的时候,水温每10年仅仅上升了0.101摄氏度。在同期,气候区移动的中位速度是每101.07公里,这比报告的陆地和海洋环境的速度慢一个数量级。这组作者发现,几种冷水脊椎物种占据了特点是气候速度(climate velocities)特别慢的栖息地。3种有物种保护担忧的物种——强壮红点鲑、克氏鲑和尾蟾——栖息在气候速度小于每100.5公里的环境中。这组作者说,这些结果提示,山地溪流可能为物种提供针对变暖的气候的效应的缓冲,而这类避难溪流中的生物多样性可能在未来的一个世纪中持续存在。

参阅文献:

Slow climate velocities of mountain streams portend their role as refugia for cold-water biodiversity

PNAS April 4, 2016,10.1073/pnas.1522429113 

The imminent demise of montane species is a recurrent theme in the climate change literature, particularly for aquatic species that are constrained to networks and elevational rather than latitudinal retreat as temperatures increase. Predictions of widespread species losses, however, have yet to be fulfilled despite decades of climate change, suggesting that trends are much weaker than anticipated and may be too subtle for detection given the widespread use of sparse water temperature datasets or imprecise surrogates like elevation and air temperature. Through application of large water-temperature databases evaluated for sensitivity to historical air-temperature variability and computationally interpolated to provide high-resolution thermal habitat information for a 222,000-km network, we estimate a less dire thermal plight for cold-water species within mountains of the northwestern United States. Stream warming rates and climate velocities were both relatively low for 1968–2011 (average warming rate = 0.101 °C/decade; median velocity = 1.07 km/decade) when air temperatures warmed at 0.21 °C/decade. Many cold-water vertebrate species occurred in a subset of the network characterized by low climate velocities, and three native species of conservation concern occurred in extremely cold, slow velocity environments (0.33–0.48 km/decade). Examination of aggressive warming scenarios indicated that although network climate velocities could increase, they remain low in headwaters because of strong local temperature gradients associated with topographic controls. Better information about changing hydrology and disturbance regimes is needed to complement these results, but rather than being climatic cul-de-sacs, many mountain streams appear poised to be redoubts for cold-water biodiversity this century.

 
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