Central American climate and microrefugia: A view from the last interglacial

The Last Interglacial (c. 128,000 to 115,000 years ago) was the last time when global temperatures may have been higher than those of the Holocene, but little is known about vegetation change or paleoclimate during that period in Central America. A new fossil pollen record from the lowland setting of El Valle, Panama, spanned the period from 137,000 to 98,000 years ago. We used multivariate analysis of modern and fossil pollen samples to provide the first regional quantification of Last Interglacial temperature and precipitation change and found mean annual temperatures were c. 1–2 °C warmer than modern, while precipitation was mostly similar to modern. The montane genus Quercus was intermittently present throughout the interglacial period, leading to the inference that this dispersal-limited taxon was surviving in microrefugia. Both charcoal and the early successional genus Cecropia were noticeably rare in the last interglacial compared with the Holocene. The modern absence of Quercus from Central Panama does not appear to be the product of interglacial warming, but rather a result of dry conditions in the late Holocene and human activity. It is suggested that humans greatly increased fire frequency, thereby favoring Cecropia and eliminating Quercus from the lower portion of its elevational range.