Quantitative Late Quaternary Climate Reconstruction from Plant Macrofossil Communities in Western North America

Abstract

The Late Quaternary packrat (Neotoma spp.) midden plant macrofossil record in western North America is an exceptional record of biotic change that provides strong evidence of past climate. In this study, we generate quantitative estimates of climate from plant community composition of more than 600 individual paleomiddens over the past 50,000 years. Here we present the first large-scale application of CRACLE (Climate Reconstruction Analysis using Coexistence Likelihood Estimation), a quantitative climate inference method that uses plant community composition as a climate proxy under the individualistic concept of plant community assembly. The results are spatiotemporally specific estimates of temperature, precipitation, available moisture, and seasonal patterns that are consistent with well understood global climate patterns but provide previously unavailable detail and precision of the regional paleoclimate in western North America. Rapid warming is estimated at the Pleistocene-Holocene transition, at a conservative estimate of ca. 1°C per millennium. Previously projected future temperature increases suggest a rate of increase of more than 2°C over the next century, an astonishing 10× the rate experienced at any point during the past 50,000 years in Western North America. These analyses form a baseline demonstration of how the growing paleoecological record of packrat midden plant macrofossils can provide quantitative estimates of paleoclimate that aid in understanding the complexities of, and biotic responses to the regional climate system. This work is the first synthetic application of any paleoclimate estimation method to packrat midden plant macrofossils.

Paleo‐metagenomics of North American fossil packrat middens: Past biodiversity revealed by ancient DNA

“…Here, we show that packrat middens up to ~30,000 years old contain recoverable DNA that is taxonomically consistent with macrofossils found in these deposits. Further investigation into the taxonomic composition of middens with aDNA analysis throughout the region could refine our understanding and the timeline of past climate change (Harbert & Nixon, ) and species migration and extinction, and this will better inform the study of the effects of current and future climate change. Deeper sequencing and targeted generation of reference sequences should improve classification precision in future work by providing clearer and more easily verifiable taxonomic classifications for degraded and mixed aDNA samples from packrat middens.…”

cRacle: R Tools for Estimating Climate from Vegetation

“…CRACLE modeling was recently applied to the estimation of paleoclimate using Late Quaternary (<50ka – kilo anuum ) plant macrofossils from packrat ( Neotoma spp.) middens in Western North America (Harbert, Nixon 2018). Analysis of the packrat midden paleoclimate estimates revealed a history of rapid climate change during and just after the Late Pleistocene deglaciation, followed by Holocene warm and dry periods of 1-2°C above the modern (1950- 2000) averages (Harbert and Nixon, 2018)…”

Exceptionally preserved asphaltic coprolites expand the spatiotemporal range of a North American paleoecological proxy

“…Photographs courtesy of Carrie Howard.Scientific RepoRtS |(2020) 10:5069 | https://doi.org/10.1038/s41598-020-61996-y www.nature.com/scientificreports www.nature.com/scientificreports/DiscussionCoprolites provide one of the most direct windows into past behaviors and ecological interactions available in the paleontological record. Neotoma middens and the coprolites and plant macrofossils contained within them have come to define our understanding of Quaternary vegetation in the arid southwestern US32 . While the…”