Doctoral Dissertation Improvement Award: Aridification and Environmental Change

生物多样性的内在价值和经济价值使物种灭绝成为一个重要的社会问题。为了保护现有的物种多样性，了解过去和现在生物多样性丧失的驱动因素是很重要的。考古学和古生态学为人类、其他生物和气候之间导致灭绝的相互作用提供了相关的、长期的视角。这个项目将回答几个长期存在的问题，即干燥的气候和早期人类对马达加斯加的殖民以及相关的引进物种可能导致岛上大型动物的灭绝。例如，人类在多大程度上捕猎现已灭绝的动物？引进的动物是否与现已灭绝的本地动物竞争？引进的动物是否比本地动物更耐旱？认识到区域变化来源之间的反馈是一项挑战，但是对马达加斯加数据集的案例研究广泛适用于研究面对干旱化的生物之间过去的相互作用。鉴于这项研究与马达加斯加西南部干旱地区的环境问题和正在制定的与干旱有关的政策的相关性，社区和地方政府的外联是项目的优先事项。这项跨学科工作涉及马达加斯加大学的学生和教师，通过这项研究的实地部分培训的学生将获得适用于数据收集和自然资源管理的技能。这项研究调查了人类和引进物种在新环境中的到来可能导致过去和正在进行的生物多样性丧失的许多方式中的一些。该项目的实地部分侧重于马达加斯加西南海岸。该地区是研究与人类活动相关的环境变化的理想地点，因为人类和人类引进的动物（如山羊、猪、牛、狗、猫和老鼠）在几千年前就到达了该岛，而且这条海岸线上有大量灭绝的特有动物（如侏儒河马、巨型乌龟、象鸟和巨型狐猴）的骨头。对一系列有人类活动痕迹的沿海池塘进行调查和挖掘，有助于恢复过去人类活动和生物多样性丧失的物质记录。对野外工作和博物馆收藏的骨骼进行放射性碳定年，为推断人类、其他生物和环境变化之间过去的相互作用提供了必要的时间控制。对放射性碳定年骨蛋白的一系列化学分析被用来追踪生物体的饮食和环境的各个方面。这些分析，再加上一项单独资助的努力，通过对古代湖泊沉积物的化学分析来重建该地区过去的气候，使研究过去人类活动和气候变化之间潜在的协同作用成为可能，气候变化可能导致了岛上过去的灭绝。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The intrinsic and economic values of biodiversity make species extinction a significant societal concern. To conserve the existing variety of species, it is important to understand past and present drivers of biodiversity loss. Archaeology and paleoecology provide relevant, long term perspectives on interactions among humans, other organisms, and climate that contribute to extinctions. This project will answer several longstanding questions regarding how a drying climate and the early colonization of Madagascar by humans and associated introduced species may have contributed to past extinctions of large animals on the island. For example, to what extent did humans hunt the now extinct animals? Did introduced animals compete with now-extinct natives, and were introduced animals drought-tolerant relative to natives? Recognizing feedbacks among sources of regional change is a challenge, but this case study of datasets from Madagascar is broadly applicable to the study of past interactions among organisms in the face of aridification. Given the relevance of this research to present environmental concerns and the ongoing development of drought-related policy in arid southwest Madagascar, community and local government outreach is a project priority. This interdisciplinary work involves students and faculty at Malagasy universities, and the students trained through the field component of this research will gain skills applicable to data gathering and natural resource management.This research investigates some of the many ways in which the arrival of humans and introduced species in a novel environment may have contributed to past and ongoing biodiversity loss. The field component of this project focuses on the coast of southwest Madagascar. This region is ideal for studies of environmental changes associated with human activity, because humans and human-introduced animals (e.g. goats, pigs, cattle, dogs, cats, and rats) arrived on the island several thousand years ago, and the bones of extinct endemic animals (e.g. pygmy hippos, giant tortoises, elephant birds, and giant lemurs) are abundant along this coastline. Survey and excavation of a series of coastal ponds with traces of past human presence serve to recover the material record of past human activity and biodiversity loss. Radiocarbon dating of bone recovered from fieldwork and museum collections provides the chronological control that is necessary to infer past interactions among humans, other organisms, and environmental change. A series of chemical analyses of radiocarbon-dated bone protein is used to trace aspects of organisms' diets and environments through time. These analyses, coupled with a separately-funded effort to reconstruct the past climate of the region through the chemical analysis of ancient lake sediments, make it possible to examine potential synergies between past human activity and the changing climate that may have driven past extinctions on the island.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.