Novel geochemical methods for assessing trophic ecology in modern and ancient ecosystems

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Trophic (consumer-prey) dynamics are the essential building blocks of ecosystems. These interactions drive ecosystem functionality and biogeochemical cycles globally, and are sensitive to the impacts of climate change and human activity in the past and present. Geochemical (isotopic) proxies for diet and trophic interactions are critical tools for tracing these dynamics without direct observation and are essential for a range of fields from conservation to paleosciences. In simple trophic systems, traditional stable isotopes such as carbon (d13C) and nitrogen (d15N) are often sufficient to trace prey sources. However, in more complex systems, such as environments with diverse carnivores or those involving humans, trophic relationships remain partially or completely unresolved in isotopic studies. African terrestrial ecosystems are complex, hosting extraordinarily diverse mammalian communities. These ecosystems shaped the evolution of our species, yet now face risk of collapse as a result of increasing anthropogenic pressures. Yet, our understanding of trophic ecology in these complex ecosystems using current isotopic proxies yields ambiguous results, limiting our understanding of how these ecosystems have changed over time and when human impacts began. My 5-year research plan is to (1) to investigate changes in trophic position and diet source in mammals using recently developed trophic proxies of organic (d15NAA) and inorganic (d26Mg and d44Ca) biological tissues in African ecosystems, and (2) apply these approaches to investigations of human dietary change in the past in order to understand anthropogenic impact in prehistory. This project will lay the groundwork for understanding trophic connections in complex ecosystems (e.g., multi-tier trophic systems that include human impacts), illustrate shifting anthropogenic pressures from ancient to modern times, and create an analytical framework that can be used in complex terrestrial ecosystems globally. This project addresses a fundamental limitation of (paleo)ecological studies using new geochemical methods for understanding trophic links in systems where these links have been difficult to resolve with traditional methods. This project will also address fundamental questions of human diet and anthropogenic impacts in prehistory. This work will capitalize on the PI's >10 years of research experience and connections in eastern Africa, and will provide opportunities for students to conduct museum and lab-based research on these projects. We will also host a symposium on our work at the National Museums of Kenya in the project's final year to share our findings and create networking opportunities for young international scholars. This project will foster international collaborations, including academics from eastern Africa, as an ongoing effort to promote equity among the global community of scholars.