Holocene Fires in Costa Rica

Charcoal fragments in soils and sediments document Holocene fires in the rain forests of the La Selva Biological Station in the northern Caribbean lowlands of Costa Rica, and in the paramo surrounding Cerro Chirrip6 in the Cordillera de Talamanca. Radiocarbon determinations on soil charcoal from La Selva and charcoal-rich lake sediment from Chirrip6 cluster at 2430 yr B.P. and at 1110-1180 yr B.P.; dates in each cluster are coeval, suggesting that the rain forest and paramo fires occurred at similar times. Fires at La Selva were likely set by human activity but may have spread into intact rain forest during exceptionally dry periods; fires at Chirrip6 were set by people or lightning during what may have been lower lake stands. The drought periods suggested by our charcoal samples may have been associated with short-term atmospheric anomalies such as El Niiio, or with longer-term shifts in climate.