South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria 0001, South Africa.
DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa.
Proc Natl Acad Sci U S A. 2019 Jul 9;116(28):14065-14070. doi: 10.1073/pnas.1821312116. Epub 2019 Jun 24.
Birds inhabiting hot, arid regions are among the terrestrial organisms most vulnerable to climate change. The potential for increasingly frequent and intense heat waves to cause lethal dehydration and hyperthermia is well documented, but the consequences of sublethal fitness costs associated with chronic exposure to sustained hot weather remain unclear. Using data for species occurring in southern Africa's Kalahari Desert, we mapped exposure to acute lethal risks and chronic sublethal fitness costs under past, present, and future climates. For inactive birds in shaded microsites, the risks of lethal dehydration and hyperthermia will remain low during the 21st century. In contrast, exposure to conditions associated with chronic, sublethal costs related to progressive body mass loss, reduced nestling growth rates, or increased breeding failure will expand dramatically. For example, by the 2080s the region will experience 10-20 consecutive days per year on which Southern Pied Babblers () will lose ∼4% of body mass per day, conditions under which this species' persistence will be extremely unlikely. Similarly, exposure to air temperature maxima associated with delayed fledging, reduced fledgling size, and breeding failure will increase several-fold in Southern Yellow-billed Hornbills () and Southern Fiscals (). Our analysis reveals that sublethal costs of chronic heat exposure are likely to drive large declines in avian diversity in the southern African arid zone by the end of the century.
栖息在炎热干旱地区的鸟类是最容易受到气候变化影响的陆生生物之一。越来越频繁和强烈的热浪导致致命脱水和体温过高的可能性已经得到充分记录,但与持续高温慢性暴露相关的亚致死适应成本的后果仍不清楚。利用发生在南非卡拉哈里沙漠的物种数据,我们绘制了在过去、现在和未来气候下急性致死风险和慢性亚致死适应成本的暴露情况。对于在阴凉微生境中不活跃的鸟类,在 21 世纪,致命脱水和体温过高的风险将保持在低水平。相比之下,与渐进性体重减轻、雏鸟生长率降低或繁殖失败相关的慢性、亚致死适应成本相关的暴露情况将急剧增加。例如,到 2080 年代,该地区每年将有 10-20 天连续出现,南非斑胸草雀()每天将损失约 4%的体重,在这种情况下,该物种的生存将极不可能。同样,与出雏延迟、雏鸟体型减小和繁殖失败相关的空气温度极值的暴露情况,在南非黄嘴犀鸟()和南非福斯科斯()中也将增加数倍。我们的分析表明,到本世纪末,慢性热暴露的亚致死适应成本可能导致南部非洲干旱地区鸟类多样性大量减少。