Data from: Biotic and climatic velocity identify contrasting areas of vulnerability to climate change

Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth’s surface to maintain constant climatic conditions. However, “analog-based” velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961–2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site’s future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.能够综合气候变化复杂影响的各类指标，是绘制生物多样性未来受威胁格局、预测哪些物种可就地适应新气候条件、扩散并在新近适宜的气候区域定居，抑或是面临绝灭前景的核心工具。此类指标中应用最广泛的是气候变迁速度（velocity of climate change），其估算物种为维持恒定气候条件，需在地球表面迁移的速率。然而，基于相似气候的迁移速度（analog-based velocities）——即估算未来相似气候所在区域与当前位点的实际距离——与基于局地气候梯度的常规迁移速度可能得出截然不同的结果。此外，气候变迁速度仅反映生物群落面临的气候变化暴露程度，而由此产生的生物效应则取决于单个物种的敏感性，这在一定程度上可通过其气候生态位宽度体现。由此推动了生物迁移速度（biotic velocity）的开发：该指标利用预测的物种分布范围变化数据，估算物种为追踪其气候生态位所需迁移的速率。我们针对1961年至2100年的西半球区域，计算了气候变迁速度与生物迁移速度，并将结果应用于典型生态与保护规划问题，以展示此类基于相似气候的指标在揭示大尺度气候暴露与敏感性格局方面的应用潜力。针对2954种鸟类、哺乳类及两栖类的生物迁移速度地理格局，在北温带与北方针叶林带与气候变迁速度存在差异。但二者均在低纬度地区达到峰值，这意味着赤道地区物种面临的威胁同时源于未来较高的气候变迁速度，以及这些区域物种狭窄的气候耐受幅度——而这些区域当前的季节与年际气候变率本就较低。生物迁移速度与气候变迁速度分别近似于物种迁移速率的上下限，可分别为物种及本地适应种群的保护提供参考；结合反向迁移速度（backward velocity，即适应某区域未来气候的拓殖者来源地距离），则可助力应对气候变化下多尺度的生物多样性保护工作。