2025-11-12 ジョージア工科大学(Georgia Tech)
<関連情報>
- https://research.gatech.edu/30-year-snapshot-pacific-northwestern-birds-shows-their-surprising-resilience
- https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.70193
- https://jem-online.org/index.php/jem/article/view/232
太平洋岸北西部の鳥類は、30年間の気温上昇に応じて、その生息数を斜面の上流に移動させた Pacific Northwest birds have shifted their abundances upslope in response to 30 years of warming temperatures
Benjamin G. Freeman, Harold N. Eyster, Julian M. Heavyside, Daniel A. Yip, Monica H. Mather, F. Louise Waterhouse
Ecology Published: 21 September 2025
DOI:https://doi.org/10.1002/ecy.70193
Abstract
Mountain species are predicted to respond to warming temperatures by moving to higher elevations that remain relatively cool. Species can track warming by shifting their entire distributions upwards (the “escalator to extinction” hypothesis) or by increasing in abundance in the upper portion of their elevational range while maintaining stable elevational limits (the “upslope lean” hypothesis). Alternatively, mountain species may not change their abundance or distribution despite climate change (the “persist-in-place” hypothesis). Here we evaluate these three contrasting hypotheses by analyzing responses of breeding forest bird species to three decades of warming in southwestern British Columbia, Canada. Consistent with the upslope lean hypothesis, species’ optimum elevations (elevations of highest abundance) increased by an average of 126 m, approximately tracking upslope movements in temperature isotherms. In contrast, species’ elevational range limits were stable on average, contra the escalator to extinction hypothesis. Many individual species had stable distributions and abundances, and species with upslope abundance increases typically maintained stable abundances within the lower elevation portions of their range. Taken together, most species in our study region appear to be responding neutrally or favorably to warming temperatures. Nevertheless, one mountain species, the Canada Jay, Canada’s national bird, is declining and vulnerable to the escalator to extinction within our study region. Overall, we emphasize the importance of empirical data—and abundance data in particular—when evaluating mountain species’ vulnerability to climate change.
ブリティッシュコロンビア州南部の沿岸原生林における標高と生物地理気候帯に関連した鳥類の分布と個体数 Distribution and abundance of birds relative to elevation and biogeoclimatic zones in coastal old-growth forests in southern British Columbia
F. Louise Waterhouse,Monica H. Mather,Dale Seip
Journal of Ecosystems & Management Published:2003-06-03
DOI:https://doi.org/10.22230/jem.2003v2n2a232
Abstract
This study examined birds and their association with forest structure and elevation in 1992 and 1993. The research sites were located in old-growth forest stands (251+ years) distributed between 400 and 1500 m elevation in south coastal British Columbia. The use of simple and multiple regressions revealed that the variation in mean abundance of most bird species was in part explained by elevation, and was likely due to stand structure and other factors (e.g., forage productivity) that vary with the elevational gradient. However, total bird abundance and richness responded weakly to elevation; instead, density of huge snags (≥ 100 cm DBH) per hectare more consistently accounted for the variation in these two measures.
Distributions of bird species are described according to two biogeoclimatic zones—the Coastal Western Hemlock and the Mountain Hemlock. Biogeoclimatic classification, which is based on plant associations and climate, is used for forest management in British Columbia. Mean abundance of 10 bird species differed significantly between the biogeoclimatic zones in at least one of the study years. Biogeoclimatic zones also effectively classified bird species into two different communities using multidimensional scaling and mean similarity analysis. However, richness and total bird abundance did not differ significantly between zones indicating that community structure was similar, although composition and dominance differed by zone. The authors, therefore, suggest that representation of old-growth forest by biogeoclimatic zone helps maintain bird diversity. To maintain the observed distributions of bird species, however, oldgrowth habitats should be represented over the entire elevational gradient and include variation in forest stand structure.
