75 Climate Change Impacts on Desert Ecosystems: Paleoecological Lesson from the Late Pleistocene in the Great Basin, Nevada

Faculty Mentor: Larry Coats (Geography, University of Utah)

We are experiencing extreme changes in climate as never seen before. These changes have acute impacts on the ecosystems we depend upon for survival, therefore we must understand how these ecosystems will respond to the profound climate disruption that may be coming our way. In this study, we use paleoecological tools to research the effects of previous climate shifts in Earth’s history so we can predict how ecosystems will respond to present changes. We are focused on studying the Late Pleistocene and transition into the Holocene Epoch because of the characteristic successive, short-term, abrupt changes in climate. Solutional caves with stratified sediment (such as Ladder Cave in the central Great Basin in Nevada) are a common part of the environment in western North America and preserve microbiota remains, plant macrofossils, and pollen grains. We can see these quick transitions through changes in floral macrofossil assemblages between sediment levels in Ladder Cave. We examine small-scale changes in desert ecosystems from ~50,000 years ago to present day as recorded by changing biota during climatic shifts. In 2023, Dr. Steve Emslie, Professor Larry Coats, and Dr. Jim Mead excavated several test pits in Ladder Cave and Test Pit 4 reached a depth of 140 cm and has strata in chronological order. The upper 70cm of the sediment from this test pit has been processed and analyzed in the University of Utah Records of Environment and Disturbance (RED) Lab, while the lower 70 cm of sediment is being processed and analyzed at UNC Wilmington. Sediment is dry screened on site and wet screened with Endecotts Test Sieves at 0.5 mm mesh before drying. Then, we pick through the sediment under magnification and organize macrofossils by preliminary identification. While our focus is on floral macrofossil remains and what they tell us about past climate, faunal macrofossil material is being processed at both UNC Wilmington and The Mammoth Site, South Dakota. By identifying species and quantifying macrofossils, we can make inferences about Late Pleistocene paleoclimates. Preliminary radiocarbon data from the University of Georgia Center for Isotope Studies (UGAMS) suggests that a continuous record of biotic change is available from ~50,000 years ago to present, with surface layers actively accumulating. Preliminary analyses of faunal remains from Ladder Cave and nearby caves have revealed an extensive list of herpetofauna, mammals and avifauna. We are continuing preliminary plant identification as we work through each level which has revealed great diversity in vegetation between levels as we study the transition from glaciation in the Pleistocene to the draining of Lake Bonneville and the transition into the Holocene Epoch. By focusing on the study of past environmental change, we will understand how ecosystem components react independently and altogether to reflect climate changes.