Abstract
The southeastern United States endures environmental change from human population increase, climate change, and land use alterations creating the need to understand baseline conditions and environmental patterns prior to human impacts. While paleoenvironmental data can be reconstructed from a variety of archives (e.g. lake sediments, tree rings, speleothems), some geographic areas contain fewer of such records. One archive capable of recording moisture regimes and other paleoenvironmental changes over millennia but has received little attention relative to other climate proxies, are bat guano deposits in cave systems. Bat guano deposits are found in many cave environments in the southeastern United States and can be used as an archive of paleoenvironmental data including precipitation, vegetation, and aspects associated with the ecology of bats. Here, we present a 12,000-year record of paleoenvironmental change based on δ2H stable isotopes in a guano core collected from Cave Springs Cave in Alabama, USA. Results suggest distinct shifts in moisture during the lower Holocene/upper Pleistocene (9,551 – 12,131 cal yr BP) (δ2H values -86.82 – -77.70) and during the middle Holocene (3,886 – 9,351 cal yr BP) (δ2H values -125.74 – -80.63), roughly coinciding with the Holocene Climatic Optimum (HCO) time interval (5,000 – 9,000 cal yr BP). During the last 4,000 years, conditions in the region shifted once again in the southeastern United States region. Climate inferences based on guano δ2H are consistent with the role of atmospheric moisture on regional vegetation changes suggested by previous pollen records obtained from lake sediment cores. This study suggests bat guano δ2H may be a reliable method to provide a long-term paleoclimate record.
Long-term exposure to PM2.5 major components and mortality in the southeastern United States
