Pre-Columbian land-use history in Costa Rica: a 3000-year record of forest clearance, agriculture and fires from Laguna Zoncho

We analysed pollen and charcoal in a lake-sediment core from Laguna Zoncho, a small mid-elevation lake in southernmost Costa Rica. The record provides evidence of 3000 years of human occupation, forest clearance, agriculture and fires in the area. Laguna Zoncho is located 2 km from the Las Cruces Biological Station, and results are relevant to understanding the likely extent of prehistoric disturbance within the premontane rain forests of this biological reserve. Pollen grains of Zea mays in the basal sediments of the Zoncho core constitute the oldest botanical evidence of maize cultivation in southern Costa Rica. The presence of maize pollen in almost every sample analysed indicates nearly continuous occupation of the lake basin for 3000 years. Charcoal abundances and percentages of pollen grains and spores of forest and disturbance taxa fluctuate strongly downcore, reflecting variable intensities of past human impact. Forest clearance and burning by indigenous people were most marked between 3240 and 460 cal. yr BP. Sediments deposited subsequently indicate forest regeneration and few, if any, fires. However, indigenous cultivation of maize continued on a small scale until European settlement in the twentieth century.