Fire history across the Little Ice Age in southern Pacific Costa Rica

Abstract

We present two high-resolution records of Late Holocene (Meghalayan) fire history from lakes in the lowlands of southern Pacific Costa Rica and compare them with evidence of pre-Columbian agriculture in the same cores and with records of regional paleoclimate. Macroscopic charcoal influx at Laguna Danta and Laguna Carse shows several major and minor peaks for approximately the last ~ 800 years, but does not show the decline at the time of the Little Ice Age and Spanish contact evident in other charcoal records from the region. Stable carbon isotope values in sediments indicate that agricultural activity at Laguna Danta declined following the onset of the Little Ice Age, but the association between fire and indigenous agriculture at the study sites is not strong. Instead, drought appears to be a primary driver of fire in the lowlands of southern Pacific Costa Rica. Some peaks in macroscopic charcoal at Laguna Danta coincide with shifts in the mean latitudinal position of the Intertropical Convergence Zone in the Caribbean as reconstructed from the Cariaco Ti record. We also identify a decrease in the stable nitrogen isotope values of lake sediments associated with increased fire activity, a pattern also documented in temperate ecosystems. We interpret our charcoal records to indicate both human use of fire in agricultural settings and wildfires in intact forests driven by regional changes in climate.