Data from: Old-growth forests buffer climate-sensitive bird populations from warming

Aim: Habitat loss and climate change constitute two of the greatest threats to biodiversity worldwide, and theory predicts that these factors may act synergistically to affect population trajectories. Recent evidence indicates that structurally complex old-growth forest can be cooler than other forest types during spring and summer months, thereby offering potential to buffer populations from negative effects of warming. Old growth may also have higher food and nest-site availability for certain species, which could have disproportionate fitness benefits as species approach their thermal limits. Location: Pacific Northwestern United States. Methods: We predicted that negative effects of climate change on 30-year population trends of old-growth-associated birds should be dampened in landscapes with high proportions of old-growth forest. We modelled population trends from Breeding Bird Survey data for 13 species as a function of temperature change and proportion old-growth forest. Results: We found a significant negative effect of summer warming on only two species. However, in both of these species, this relationship between warming and population decline was not only reduced but reversed, in old-growth-dominated landscapes. Across all 13 species, evidence for a buffering effect of old-growth forest increased with the degree to which species were negatively influenced by summer warming. Main conclusions: These findings suggest that old-growth forests may buffer the negative effects of climate change for those species that are most sensitive to temperature increases. Our study highlights a mechanism whereby management strategies to curb degradation and loss of old-growth forests—in addition to protecting habitat—could enhance biodiversity persistence in the face of climate warming.研究目标：生境丧失与气候变化是当前全球生物多样性面临的两大核心威胁，现有理论预测二者可产生协同作用，进而影响种群轨迹。近期研究表明，结构复杂的原始林（old-growth forest）在春夏季节的气温较其他林型更低，因此具备为种群缓解气候变暖负面影响的潜力。此外，部分物种在原始林中可获取的食物与巢址资源更为丰富，当物种接近其热耐受上限时，这类资源优势可为其带来不成比例的适合度收益。 研究区域：美国太平洋西北部。 研究方法：本研究提出假设：在原始林占比高的景观中，气候变化对与原始林伴生的鸟类30年种群趋势的负面影响将得到缓解。我们基于繁殖鸟类调查（Breeding Bird Survey, BBS）数据，针对13个鸟类物种的种群趋势，以气温变化与原始林占比为自变量构建模型。 研究结果：仅发现夏季升温对2个物种存在显著的负面影响。但在这两个物种中，升温与种群下降之间的关联在以原始林为主的景观中不仅被削弱，甚至发生逆转。在全部13个物种中，原始林的缓冲效应随物种受夏季升温负面影响程度的提升而增强。 主要结论：本研究结果表明，原始林可对那些对温度升高最为敏感的物种，起到缓解气候变化负面影响的作用。本研究揭示了一种机制：除保护栖息地外，通过管理策略遏制原始林的退化与丧失，可提升生物多样性在气候变暖背景下的存续能力。