Collaborative Research: Human and non-human influences on species biodiversity in an island ecosystem

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Studying large-scale extinction events in the past can help us understand declines in global biodiversity in our modern world. In this multidisciplinary project, the investigators want to understand what triggered the recent extinction of all of Madagascar's large native vertebrates, including its chimpanzee- and gorilla-sized lemurs, enormous 'elephant birds,' and horned crocodiles. The discovery of extraordinary deposits of fossils and stalagmites in previously-unexplored flooded and dry caves at Tsimanampesotse National Park (TNP) in southwestern Madagascar has opened new opportunities for researchers to address this question. An international team of anthropologists, geologists and ecologists will work with cave divers to retrieve and study fossils and stalagmites from the flooded caves and nearby dry deposits. By taking small samples of rock from stalagmites and studying their chemistry, the team will be able to reconstruct with great precision changes in habitat and rainfall over the past 50,000 years. Team members will also document changes in the presence or absence of small animals that may be excellent indicators of habitat transformation. Through this work, they will identify specific turning points in the catastrophic decline and extinction of Madagascar's large vertebrates, which will have broad implications for how to avoid future extinctions on the island and elsewhere. The team will support public science outreach with creation of 3D maps of the flooded caves and fossil deposits, and multi-language, multi-media educational displays. The displays will focus on conservation, and how understanding the past can inform the future. Finally, this project will support the doctoral dissertations of three graduate students, and build future opportunities for international collaborative research. The investigators will utilize state-of-the-art techniques from anthropology, ecology, cave science and paleoclimatology to tease apart how environmental changes and human activities affect communities of plants and animals. This work is challenging, especially since natural aridification (through reduced rainfall) and human disturbance (through setting fires, cutting trees, raising cattle or other introduced domesticated animals, and planting crops) can have similar devastating effects on the distribution and abundance of wild plants and animals. However, stalagmites preserve precisely-datable records of changes in local rainfall and vegetation. Consequently, it is possible to know when rainfall and vegetation co-varied, and when vegetation changed independent of rainfall, implying that some other agent, such as humans, was responsible. Bones and teeth of animals can preserve datable evidence of the diets, activities, movements and habitats of species that have survived, and those that have not. Sometimes traces on the surfaces of fossils themselves preserve evidence of how individuals died - for example, by succumbing to a predatory bird, carnivore or human. This project will tease apart the relative importance of environmental change and human activities, and build a chronology of the survival and extinction of species. Advances in the science of the chemistry of rocks, bones, and teeth, coupled with the old-fashioned tools of paleontological analysis (identifying fossils and recording their associations) have made all of this possible. 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.