A late-Holocene sedimentary record of vegetation, fire, and environmental history from Barbuda, Lesser Antilles

Background/Question/Methods

Interpretations of sedimentary records from the Caribbean and tropical America agree that the Holocene was a time of climate variability and environmental change. While Hispaniola remains the most studied Caribbean island, the islands as a whole have few paleorecords and fewer vegetation histories. Additionally, pollen records from the Caribbean islands are predominately from mid- and high-elevation sites while records from lowland and coastal sites are especially rare, limiting the reconstruction of vegetation and disturbance histories of lowland tropical vegetation. Thus, lowland sites from the Caribbean islands represent a key area of study in order to examine late Holocene climate and vegetation dynamics.

This project uses paleoecological techniques to document environmental history at Freshwater Pond in Barbuda, Lesser Antilles. Our main goal was to reconstruct the vegetation, fire, and environmental history of the study site and surrounding area through the analysis micro- and macro-fossils contained in the lake sediments. We used multiple proxies including pollen, microscopic (> 10 µm) and macroscopic (> 125 µm) charcoal, ostracods, radiocarbon dating, and loss-on-ignition (LOI) to analyze an 84 cm sedimentary profile from the pond.

Results/Conclusions

Four AMS radiocarbon dates provided chronological control of the sediment profile and date the pond to at least 2130 ± 40 14C yr BP. Sixteen depth levels have been processed to isolate pollen, spores, and micro-charcoal.  Pollen and ostracods from the deepest sediments (84–65 cm) were not well preserved though these depths contain high concentrations of micro-charcoal and fungal spores, indicating regional burning and that conditions were unfavorable for the establishment of a freshwater ecosystem. Deeper sediments are dominated by pollen of Combretaceae/Melastomataceae and Solanaceae while more recent sediments are dominated by Cyperaceae and fern spores, indicative of a freshwater environment. High-resolution (1-cm) loss on ignition indicates increasing authigenic carbonate from deeper to more recent sediments. Macro-charcoal (>125 µm) was present in 17 depth levels, all above 59 cm and indicates the occurrence of local fires. Together, these multiple proxies indicate the gradual development of a freshwater lake over the last ca. 2000 14C years, suggesting an increasing Precipitation /Evaporation (P/E) ratio. Increased moisture in the region could also explain the occurrence of local fires tied to increased availability of fuels and changes in human activity on the island.