Human Response To El Nino-Driven Environmental Change

University Of Utah, Salt Lake City UT

Investigators

Abstract

Extreme variation in climate is a topic of concern across the globe. Jack Broughton and Joan Coltrain, of the University of Utah, will undertake research to study how variation in the intensity and frequency of El Niño events in northern Baja California, Mexico over the past 11,000 years influenced marine and terrestrial fish, birds, and mammals. Their research will also investigate how past peoples responded to changes in the availability of different animal resources. This research will provide novel data sets from which to anticipate change in future animal populations under a range of forecasted El Niño-related variation scenarios and thus support current and future management of marine and terrestrial animals of the eastern Pacific. The project will also reveal how human populations responded to past El Niño and provide insight into the impact of future El Niño events on coastal societies in developing countries. Although the impacts of ancient El Niño events on past human societies and animals have been documented in specific isolated cases, continuous, high-resolution, millennial-scale records of the impact of El Niño variation on animal resources and the resulting changes in the human use of North American landscapes have yet to be documented. This project will generate just such a record from a massive collection of animal bones and artifacts that was deposited over the past 11,000 years by people and raptors (hawks, eagles, owls) that occupied a rock shelter site (Abrigo de los Escorpiones) located about 100 m from the Pacific coast of northern Baja California, Mexico. The currently archived animal bone collection includes both marine and terrestrial species and represents one of the largest, well-stratified, continuous, records of climate-based changes in animal populations on the Pacific coast of North America. A rich record of artifacts and features (e.g., fire hearths, marine shell layers) attest to a substantial but intermittent human use of the shelter. The project will determine whether people abandoned the coastal site during periods with high El Niño frequencies. Such times are characterized by both warm sea-surface temperatures that disrupt marine ecosystems and increased precipitation that enhances the productivity of inland habitats. The study will involve: (1) identification of the animal bones to the species level, (2) radiocarbon dating of a large sample of the bones to establish a time-line and chronology for the deposits, (3) establishing a record of human occupational intensity of the site through artifact counts and evidence of human-caused damage on animal bones (e.g., stone tool cut marks, burning), (4) stable isotope analysis of both bones and shells to provide information on El Niño variation over the past 11,000 years, and (5) statistical analysis to determine correlations between variation in past El Niño and change in local animal and human populations.