MacDonald Andrew J, McComb Sofie, O'Neill Craig, Padgett Kerry A, Larsen Ashley E
Earth Research Institute, University of California, Santa Barbara, CA, USA.
Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, USA.
Glob Chang Biol. 2020 Oct;26(10):5459-5474. doi: 10.1111/gcb.15269. Epub 2020 Jul 28.
Global environmental change is having profound effects on the ecology of infectious disease systems, which are widely anticipated to become more pronounced under future climate and land use change. Arthropod vectors of disease are particularly sensitive to changes in abiotic conditions such as temperature and moisture availability. Recent research has focused on shifting environmental suitability for, and geographic distribution of, vector species under projected climate change scenarios. However, shifts in seasonal activity patterns, or phenology, may also have dramatic consequences for human exposure risk, local vector abundance and pathogen transmission dynamics. Moreover, changes in land use are likely to alter human-vector contact rates in ways that models of changing climate suitability are unlikely to capture. Here we used climate and land use projections for California coupled with seasonal species distribution models to explore the response of the western blacklegged tick (Ixodes pacificus), the primary Lyme disease vector in western North America, to projected climate and land use change. Specifically, we investigated how environmental suitability for tick host-seeking changes seasonally, how the magnitude and direction of changing seasonal suitability differs regionally across California, and how land use change shifts human tick-encounter risk across the state. We found vector responses to changing climate and land use vary regionally within California under different future scenarios. Under a hotter, drier scenario and more extreme land use change, the duration and extent of seasonal host-seeking activity increases in northern California, but declines in the south. In contrast, under a hotter, wetter scenario seasonal host-seeking declines in northern California, but increases in the south. Notably, regardless of future scenario, projected increases in developed land adjacent to current human population centers substantially increase potential human-vector encounter risk across the state. These results highlight regional variability and potential nonlinearity in the response of disease vectors to environmental change.
全球环境变化正对传染病系统的生态产生深远影响，人们普遍预计，在未来气候和土地利用变化的情况下，这种影响将更加显著。疾病的节肢动物媒介对温度和水分可利用性等非生物条件的变化尤为敏感。最近的研究集中在预测气候变化情景下病媒物种的环境适宜性变化和地理分布。然而，季节性活动模式或物候的变化也可能对人类接触风险、当地病媒数量和病原体传播动态产生巨大影响。此外，土地利用的变化很可能以气候变化适宜性模型不太可能捕捉到的方式改变人与病媒的接触率。在这里，我们利用加利福尼亚州的气候和土地利用预测以及季节性物种分布模型，来探究北美西部主要的莱姆病病媒——西部黑腿蜱（太平洋硬蜱）对预测的气候和土地利用变化的响应。具体而言，我们研究了蜱寻找宿主的环境适宜性如何随季节变化，加利福尼亚州不同地区季节性适宜性变化的幅度和方向如何不同，以及土地利用变化如何改变该州各地人类接触蜱的风险。我们发现，在不同的未来情景下，加利福尼亚州境内病媒对气候变化和土地利用变化的响应存在区域差异。在更炎热、干燥的情景以及更极端的土地利用变化下，加利福尼亚州北部寻找宿主的季节性活动的持续时间和范围增加，但在南部则减少。相反，在更炎热、湿润的情景下，加利福尼亚州北部寻找宿主的季节性活动减少，但在南部增加。值得注意的是，无论未来情景如何，预计当前人口中心附近已开发土地的增加将大幅增加该州各地人类与病媒接触的潜在风险。这些结果凸显了病媒对环境变化响应的区域变异性和潜在非线性。
