Among the most widely predicted climate change-related impacts to biodiversity are geographic range shifts, whereby species shift their spatial distribution to track their climate niches. A series of commonly articulated hypotheses have emerged in the scientific literature suggesting species are expected to shift their distributions to higher latitudes, greater elevations, and deeper depths in response to rising temperatures associated with climate change. Yet, many species are not demonstrating range shifts consistent with these expectations. Here, we evaluate the impact of anthropogenic climate change (specifically, changes in temperature and precipitation) on species’ ranges, and assess whether expected range shifts are supported by the body of empirical evidence. We conducted a Systematic Review, searching online databases and search engines in English. Studies were screened in a two-stage process (title/abstract review, followed by full-text review) to evaluate whether they met a list of eligibility criteria. Data coding, extraction, and study validity assessment was completed by a team of trained reviewers and each entry was validated by at least one secondary reviewer. We used logistic regression models to assess whether the direction of shift supported common range-shift expectations (i.e., shifts to higher latitudes and elevations, and deeper depths). We also estimated the magnitude of shifts for the subset of available range-shift data expressed in distance per time (i.e., km/decade). We accounted for methodological attributes at the study level as potential sources of variation. This allowed us to answer two questions: (1) are most species shifting in the direction we expect (i.e., each observation is assessed as support/fail to support our expectation); and (2) what is the average speed of range shifts? We found that less than half of all range-shift observations (46.60%) documented shifts towards higher latitudes, higher elevations, and greater marine depths, demonstrating significant variation in the empirical evidence for general range shift expectations. For the subset of studies looking at range shift rates, we found that species demonstrated significant average shifts towards higher latitudes (average = 11.8 km/dec) and higher elevations (average = 9 m/dec), although we failed to find significant evidence for shifts to greater marine depths. We found that methodological factors in individual range-shift studies had a significant impact on the reported direction and magnitude of shifts. Finally, we identified important variation across dimensions of range shifts (e.g., greater support for latitude and elevation shifts than depth), parameters (e.g., leading edge shifts faster than trailing edge for latitude), and taxonomic groups (e.g., faster latitudinal shifts for insects than plants). Despite growing evidence that species are shifting their ranges in response to climate change, substantial variation exists in the extent to which definitively empirical observations confirm these expectations. Even though on average, rates of shift show significant movement to higher elevations and latitudes for many taxa, most species are not shifting in expected directions. Variation across dimensions and parameters of range shifts, as well as differences across taxonomic groups and variation driven by methodological factors, should be considered when assessing overall confidence in range-shift hypotheses. In order for managers to effectively plan for species redistribution, we need to better account for and predict which species will shift and by how much. The dataset produced for this analysis can be used for future research to explore additional hypotheses to better understand species range shifts.

中文翻译：

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气候变化和生物多样性的全球重新分配：对预期范围变化的实证支持的巨大差异

最广泛预测的与气候变化相关的对生物多样性的影响是地理范围变化，物种由此改变其空间分布以追踪其气候生态位。科学文献中出现了一系列普遍阐明的假设，表明物种预计会将其分布转移到更高的纬度、更高的海拔和更深的深度，以应对与气候变化相关的气温上升。然而，许多物种并没有表现出与这些预期一致的范围变化。在这里，我们评估人为气候变化（特别是温度和降水的变化）对物种分布范围的影响，并评估预期的分布范围变化是否得到大量经验证据的支持。我们进行了系统审查，用英语搜索在线数据库和搜索引擎。研究分两个阶段进行筛选（标题/摘要审查，然后是全文审查）以评估它们是否符合资格标准列表。数据编码、提取和研究有效性评估由一组训练有素的评审员完成，每个条目都由至少一名二级评审员验证。我们使用逻辑回归模型来评估转移方向是否支持常见的范围转移预期（即转移到更高的纬度和海拔，以及更深的深度）。我们还估计了以每次距离（即公里/十年）表示的可用距离偏移数据子集的偏移幅度。我们将研究层面的方法学属性视为潜在的变异来源。这使我们能够回答两个问题：(1) 大多数物种是否朝着我们预期的方向转变（即，每个观察结果都被评估为支持/不支持我们的预期）；(2) 换档的平均速度是多少？我们发现，只有不到一半的距离偏移观测 (46.60%) 记录了向更高纬度、更高海拔和更深海洋深度的偏移，这表明一般距离偏移预期的经验证据存在显着差异。对于关注距离变化率的研究子集，我们发现物种表现出向更高纬度（平均 = 11.8 公里/十月）和更高海拔（平均 = 9 米/十月）的显着平均变化，尽管我们未能找到重要证据转移到更深的海洋深处。我们发现，个别范围偏移研究中的方法学因素对报告的偏移方向和幅度有重大影响。最后，我们确定了跨范围变化维度的重要变化（例如，比深度更支持纬度和海拔变化）、参数（例如，前缘比纬度的后缘变化更快）和分类组（例如，更快的纬度变化昆虫多于植物）。尽管越来越多的证据表明物种正在改变它们的范围以应对气候变化，但在明确的经验观察证实这些预期的程度上存在很大差异。尽管平均而言，许多分类群的迁移率显示出向更高海拔和纬度的显着移动，但大多数物种并没有朝着预期的方向迁移。在评估范围转移假设的总体置信度时，应考虑范围转移的维度和参数之间的差异，以及分类组之间的差异和方法学因素驱动的差异。为了让管理者有效地规划物种再分配，我们需要更好地解释和预测哪些物种将发生变化以及变化幅度。为该分析生成的数据集可用于未来的研究，以探索其他假设以更好地了解物种分布范围的变化。我们需要更好地解释和预测哪些物种会发生变化以及变化的幅度。为该分析生成的数据集可用于未来的研究，以探索其他假设以更好地了解物种分布范围的变化。我们需要更好地解释和预测哪些物种会发生变化以及变化的幅度。为该分析生成的数据集可用于未来的研究，以探索其他假设以更好地了解物种分布范围的变化。