Abstract

TEMOLTZIN-LORANCA, Yunuén; VELEZ, María Isabel; MORENO, Enrique  and  ESCOBAR, Jaime. Late Holocene environmental change in Lake Boquete and its watershed: human or natural causes?. Bol. Soc. Geol. Mex [online]. 2018, vol.70, n.1, pp.121-131. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2018v70n1a7.

A paleolimnological and environmental reconstruction of the volcanic Lake Boquete, in the northern highlands of Panama, was produced based on diatom, sediment, and charcoal analyses. The main aim of this study is to contribute to the understanding of the long-term anthropogenic effect in Lake Boquete and its watershed, a unique space (Gran Chiriquí region) where human occupation and nature have interacted since ~7000 yr BP (years Before Present). Our results indicate two main periods of environmental change. In the first period, from ~2840 to 1740 cal yr BP (calibrated years Before Present), the lake was under the influence of high-energy flow regimes and high erosion rates. Water pH was gradually changing from neutral to alkaline. There’s evidence of fires with four main events, some appear to be natural as indicated by the proxies, while others seem to be associated with anthropic causes most likely related to intense periods of cultivation; a particularly intense fire event is identified at ~2607 cal yr BP. We infer that during this period the lake and its watershed were under intense human impact. In the second period, from ~1740 to 197 cal yr BP, the lake was under a steady low-energy flow regime, submerged vegetation was more abundant, and pH became more acidic, fire events were less frequent. We infer that these conditions were the result of land abandonment due to human migration to the lowlands. Notwithstanding intense and frequent dry climate spells during the second period, Lake Boquete water levels were not affected, and thus, this record suggest that the main cause of environmental and limnological change in Lake Boquete and its watershed has been anthropogenic activities.

Keywords : Paleolimnology; late Holocene; diatoms; charcoal; sediment; Panama.

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