A Late Pleistocene Demographic Winter Due to Global Warming?

随着持续的气候危机和全球生物多样性的侵蚀，现在最关心的是更好地了解生态系统如何对长期气候和人为压力作出反应。在更新世晚期（约50，000 - 12，000年前），许多哺乳动物巨型动物物种（即体重> 44公斤）经历了显著的人口下降（“瓶颈”），甚至物种灭绝（如长毛猛犸象，洞熊），这与主要的气候变化和各大洲人口的增长相吻合。新技术的发展，包括古遗传学和地球化学，开始帮助我们了解这些人口崩溃及其生态后果。然而，气候和人为因素对这些人口变化的相对影响在许多情况下仍有争议。其中一个原因是，用现有方法评估过去人口动态的关键方面（如生育率）十分复杂。然而，最近的研究表明，骨骼中的钙（Ca）的同位素不同的同种个体之间的繁殖和乳酸在不同程度上。这一发现提供了一个独特的机会，研究生殖行为和生育率方面的基础上，通过化石遗骸的时间。PleistoDem将针对来自欧洲和北美不同地点的一系列现代和化石物种，如驯鹿、猛犸象和洞熊，这是首次使用这些技术进行大规模研究。钙同位素分析将整合在一个更广泛的多代理框架，包括稳定的光和锶同位素系统，以考虑在过去的生态，环境和流动性的高分辨率图片的繁殖率和行为。这个开创性的项目将提高我们对晚更新世生态变化的理解，这反过来将为预测和面对未来的生态变化提供坚实的基础。

With the ongoing climate crisis and global erosion of biodiversity, it is now of prime concern to better understand how ecosystems react to long-term climatic and anthropogenic stressors. In the late Pleistocene (~50,000-12,000 years ago), numerous species of mammalian megafauna (i.e. weight > 44 kg) experienced significant population declines ('bottlenecks'), or even total species extinction (e.g. woolly mammoths, cave bears), that coincided with major climatic changes and the growing presence of human populations in all continents. The development of new techniques, including paleogenetics and geochemistry, are beginning to help us understand these demographic collapses and their ecological consequences. However, the relative impacts of climatic and anthropogenic factors on these demographic changes remain debated in many cases. One reason for this arises from the complexity of assessing key aspects of past population dynamics (e.g. fertility rates) with currently available methods. However, recent studies have shown that the calcium (Ca) in the skeleton is isotopically different between conspecific individuals that reproduce and lactate to different extents. This discovery provides a unique opportunity to study reproduction behaviors and aspects of fertility rates through time based on fossil remains. PleistoDem will target a range of modern and fossil species, such as reindeers, mammoths and cave bears, from different locations in Europe and North America, representing the first largescale study using these techniques. Ca isotopic analyses will be integrated in a broader multi-proxy framework including stable light and strontium isotopic systems, in order to consider reproduction rates and behaviors within a high-resolution picture of past ecology, environment and mobility. This ground-breaking project will improve our understanding of Late Pleistocene ecological changes, which in turn will provide a solid base to anticipate and face future ecological changes.