Coulson Bianca, Freeman Marc T, Conradie Shannon R, McKechnie Andrew E
South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria 0184, South Africa.
Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa.
Conserv Physiol. 2025 Jun 3;13(1):coaf036. doi: 10.1093/conphys/coaf036. eCollection 2025.
Increasingly frequent and intense heatwaves are expected to elevate the risks of heat-related mortality among birds. Most studies have focused on arid-zone avifaunas and the extent to which risks will increase in other habitats, particularly humid lowlands, remains unclear. We tested the prediction that increasing air temperature and corresponding increases in humidity, and hence wet-bulb temperature ( ; lowest temperature achievable via adiabatic evaporation), will increase exposure to conditions associated with lethal hyperthermia. We empirically determined maximum ( ) for an Afrotropical forest frugivore, the trumpeter hornbill () as = 31.7 ± 1.0°C. We then modelled current and future exposure to conditions associated with > across this species' range. Under a business-as-usual emissions scenario and assuming no vegetation buffering of air temperature ( ), trumpeter hornbills will experience > for at least 1 day year over 46% of their current range, compared to 30% at present. However, the frequency of exposure will increase substantially and reach ~100 days year in parts of the southern Democratic Republic of Congo. When we incorporated the thermal buffering effect of vegetation, end-century exposure to > decreased by 0.3-66.7%, emphasizing the role of cool microsites provided by vegetation. Our analyses reveal the exposure of birds inhabiting humid environments at low latitudes to conditions associated with a risk of lethal hyperthermia under resting conditions will increase substantially in coming decades, putting a large fraction of global avian biodiversity at risk of population declines and local extinctions.
预计日益频繁和强烈的热浪将增加鸟类因高温相关原因死亡的风险。大多数研究都集中在干旱地区的鸟类群落，而在其他栖息地，尤其是潮湿低地，风险增加的程度仍不清楚。我们检验了这样一个预测：气温升高以及相应的湿度增加，进而导致湿球温度升高（通过绝热蒸发可达到的最低温度），将增加鸟类暴露于与致死性体温过高相关的环境条件下的几率。我们通过实验确定了一种非洲热带森林食果鸟类——噪犀鸟（）的最高体温（）为31.7±1.0°C。然后，我们模拟了该物种当前和未来暴露于体温高于这一临界值的环境条件下的情况。在照常排放情景下，假设没有植被对气温的缓冲作用（），噪犀鸟在其当前分布范围的46%以上地区，每年至少会有1天体温高于临界值，而目前这一比例为30%。然而，暴露频率将大幅增加，在刚果民主共和国南部部分地区将达到每年约100天。当我们纳入植被的热缓冲效应时，到本世纪末，暴露于体温高于临界值环境下的情况减少了0.3 - 66.7%，这凸显了植被提供的凉爽微生境的作用。我们的分析表明，在未来几十年里，低纬度潮湿环境中的鸟类在静息状态下暴露于与致死性体温过高风险相关的环境条件下的情况将大幅增加，这使全球很大一部分鸟类生物多样性面临种群数量下降和局部灭绝的风险。
