44-12 From Coppice to Colonization: A 6,000-Year Pollen Record of Vegetation Change at Watling's Blue Hole, San Salvador Island, The Bahamas

Abstract:

Reconstructed floral communities provide insight into past environmental conditions, ecological shifts, and localized community changes. These records help to define natural baselines, used in conservation as benchmarks of pre-human environmental conditions, and the tolerance of communities to environmental and human stressors. Such reconstructions are relevant to areas that experience human impact and are projected to see ever-increasing effects of contemporary climate change, such as The Bahamas. Bahamian pollen records are well-suited to document floral communities through time, with San Salvador Island offering an ideal setting due to its unique climatic history, relatively recent human habitation, and abundance of lacustrine catchment sites associated with significant archaeological records. Watling’s Blue Hole (WBH) is an inland blue hole near both Lucayan and colonial settlement sites, allowing for the integration of the sediment core record with the known history of human occupation and activity. Thus, WBH pollen data documents both natural and anthropogenic shifts in plant community composition.

Sediment core transects were recovered from WBH using a square-rod piston coring system capturing an approximately 6,000-year record. Core sediments yielded pollen that indicates a diverse floral community consisting of coppice species such as hardwoods (Swietenia mahagoni and Bursera sp.) and epiphytes (Tillandsia sp.). This community remained relatively stable throughout various environmental fluctuations, indicated by accompanying proxy records (e.g. sedimentology, ostracodes, XRF, grain size and LOI). Pollen counts indicate that the floral community began to gradually decrease in diversity ~1600 cal yr BP, ending with a more rapid decrease in diversity after ~700 cal yr BP. Core top pollen indicates a terrestrial floral community dominated by Asteraceae and Coccoloba sp., which likely coincides with land clearing from European colonization and plantation efforts. This community progression differs greatly from Bahamian pollen records from more northern islands, demonstrating the diversity of flora across the region. The WBH records allow us to reconstruct climatic conditions and ecologic shifts on San Salvador throughout time and define a local ecological baseline that can help determine how modern plant communities have been shaped by human influence, goals for restoration efforts, and the susceptibility of local plant communities to climatic stress.

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