La Sorte Frank A, Butchart Stuart H M, Jetz Walter, Böhning-Gaese Katrin
Cornell Laboratory of Ornithology, Cornell University, Ithaca, New York, United States of America.
BirdLife International, Cambridge, United Kingdom.
PLoS One. 2014 May 22;9(5):e98361. doi: 10.1371/journal.pone.0098361. eCollection 2014.
Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation) and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among species, and the capacity of species to utilize these gradients under climate change.
在全球气候变化的背景下，物种的地理分布正在追踪纬度和海拔方向的地表温度梯度。为了评估跨空间追踪这些梯度的机会，我们首次对世界陆地鸟类的这些梯度陡度进行了基线评估。在9014种鸟类的繁殖范围内，我们分别对所有鸟类以及一部分鸟类物种的温度沿纬度和海拔的空间梯度进行了特征描述。我们在全球范围内总结了受威胁和非受威胁物种的这些温度梯度，并确定了它们的陡度如何根据物种的地理特征（分布范围大小、形状和方向）以及气候变化下预测的温度变化而变化。非洲、北美洲和南美洲西部以及中亚的物种，其海拔温度梯度最陡，而在澳大拉西亚、印度马来群岛岛屿以及新热带低地则最浅。温带物种的纬度温度梯度最陡，尤其是在北半球。受威胁物种的海拔梯度较浅，而受威胁和非受威胁物种之间的纬度梯度差异不大。海拔梯度的强度与预测的温度变化呈正相关。对于纬度梯度，这种关系仅适用于温带物种。纬度梯度的强度能更好地由物种的地理特征预测，但主要是针对温带物种。我们的研究结果表明，受威胁物种与较浅的海拔温度梯度相关，而陡峭的纬度梯度在全年鸟类物种较少的热带以外地区最为普遍。未来的建模和缓解措施将受益于更精细粒度的分布数据的开发，以确定这些梯度在物种分布范围内是如何构建的，这些梯度在物种之间如何以及为何不同，以及物种在气候变化下利用这些梯度的能力。
