Doctoral Dissertation Research: Assessing the impacts of Pleistocene megaherbivores on vegetation stability and resilience in the Arctic

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Large herbivores play an important role in shaping modern-day Arctic ecosystems by promoting plant growth, diversity, and nutrient cycling. They may also buffer the effects of climate change on tundra ecosystems by reducing permafrost thaw and the expansion of shrubs. Until ~12,000 years ago, the Arctic was home to a diverse array of herbivores (woolly mammoths, bison, wild horses, caribou, and muskoxen) coexisting in an environment called “mammoth steppe.” It is thought that this environment was maintained by large herbivores, similar to modern African savannas. As a result, some have suggested that “rewilding” large herbivores could be a viable management strategy for the Arctic. However, we know little about how much these ecosystem properties rely on herbivore diversity because few high-latitude systems support multiple species in high numbers today. The fossil record provides a natural archive of how large herbivores and climate change influenced Arctic plant communities through time. This project builds on dissertation-level research examining a paleoecological record from Squirrel Lake, Alaska to understand the effect of prehistoric herbivore diversity on the long-term stability of Arctic ecosystems and identify the species that made up the ice age herbivore community. This project investigates the role of large herbivore diversity on Arctic ecosystem properties by creating a multi-proxy sediment record of the plant and animal diversity that surrounded Squirrel Lake (Kotzebue Sound, Alaska) in a period spanning from today to ~55,000 years before present. Sedimentary ancient DNA and density of radiocarbon dated animal remains will be used to investigate patterns of megaherbivore and plant diversity surrounding the lake through time. Proxies for vegetation, megaherbivore presence, and paleoclimates will inform the reconstruction of a chronology of megafaunal presence and environmental change. This dataset will be used to measure the effect of herbivore diversity on different components of ecosystem stability (resistance, resilience, recovery, and latitude), providing a quantitative framework to understand the impacts of these animals. This research will inform the current debate about herbivore reintroductions as a management tool for Arctic ecosystems and contribute data on the processes that shaped the mammoth steppe. The results of this study will be shared with local communities in the Kotzebue Sound area in a public, interactive exhibit, and used to build a virtual reality experience aimed at middle schoolers in Alaska and Maine.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.