A 2000-year history of forest disturbance in southern Pacific Costa Rica: pollen, spore, and charcoal evidence from Laguna Santa Elena

Paleoecological records reveal information about past changes in vegetation composition and disturbance in tropical ecosystems. These environmental histories have direct bearing on modem ecological studies and the management of protected areas, and provide information about the interaction between prehistoric peoples and their environment. In this study, I reconstruct prehistoric and historic forest disturbance and vegetation change from southern Pacific Costa Rica, in the vicinity of the Las Cruces Biological Station and the La Amistad International Park and Biosphere Reserve. Pollen and charcoal in sediments from Laguna Santa Elena reveal a nearly continuous record of human alteration of these tropical forests over the past two millennia. The basal portion of the core shows nearly intact premontane forests approximately 1800 cal. yr. BP, although there is evidence of human presence on the landscape in the form of maize pollen and charcoal. Clearing for agriculture resulted in the dominance of disturbance taxa in the watershed beginning at least 1400 cal. yr. BP. The pollen record reveals only one possible, brief hiatus from human occupation of the watershed, although secondary succession began to occur in the Laguna Santa Elena watershed prior to that time, starting about 700 cal. yr. BP. Three eruptions of nearby Volcan Bani at approximately 580, 1080, and 1440 cal. yr. BP apparently had little effect on the prehistoric populations in the immediate vicinity of the lake. Historic and modem land clearance has perpetuated a vegetation assemblage of disturbance and successional taxa. The pollen and charcoal records from Laguna Santa Elena demonstrate that this region of Costa Rica has a long history of forest clearance, which has implications for science and conservation in nearby ecological reserves and research stations, as well as for ongoing archaeological investigations in the region.