Terrestrial ecosystems of south Florida have undergone numerous human disturbances, ranging from alteration of hydroperiod, fire history, and drainage patterns through implementation of the canal system to expansion of agricultural activity to the introduction of exotic species such as Melaleuca, Australian pine, and the Pepper Tree. Over historical time, dramatic changes in the ecosystem have been documented, and these changes have been attributed to various human activities. However, cause-and- effect relationships between specific biotic and environmental changes have not been established scientifically. This project is designed to document historical changes in the terrestrial ecosystem quantitatively, to date any changes and determine whether they resulted from documented human activities, and to establish the baseline level of variability in the south Florida ecosystem to estimate whether the observed changes are greater than would occur naturally.

The ecosystem history of the Everglades over both the last 150 years and the last few millennia is being studied by analyzing floral and faunal components and charcoal from a series of short cores and surface samples collected in the Taylor Slough region of Everglades National Park, Big Cypress National Preserve, and the Water Conservation Areas. Dating of cores is provided by Lead-210 and Carbon-14. Cores are sampled at closely spaced intervals (1-2cm) for dating and examination of the microflora and fauna; these sample intervals may provide resolution in a decadal scale. Pollen and plant microfossils will be examined from each sample, and where present, mollusks, ostracodes, diatoms, foraminifers, and dinoflagellate cysts also will be studied. Quantitative data from each group will be compared to establish the timing and, ultimately, the causes of biotic change across the region. The concentration of wind-blown charcoal, which is the measure of local to regional fire history, also will be determined from each core to establish the accumulation rate of charcoal and assess temporal and regional trends in burning history. Relict plant morphology, which is retained in charcoal particles, will help identify the types of plants that burned. For each floral and faunal component, the historic record will be sampled intensively to detect biotic changes in response to human activity, and the prehistoric record will be analyzed from selected cores to determine the baseline levels of variability in the ecosystem prior to human interference.

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