Many changes in the south Florida ecosystem over the last century have been attributed to human alteration of the environment, but a scientific basis for such assumptions has been lacking. Approximately 50 cores and 80 surface samples were collected throughout the historic Everglades for pollen and peat analysis to 1) reconstruct the long-term vegetational history of the last few millennia and the natural variability of the system and 2) to identify vegetational changes over the last 150 years. Age control is provided by short-lived radioisotopes (7Be, 137Cs, and 210Pb) and radiocarbon dating; basal dates range from 1,500 BP to 3,500 BP. Cores from marine-influenced sites near Florida Bay lie within and east of Taylor Slough; comparison of down-core pollen assemblages with modern samples indicates that sparse sawgrass marshes persisted from at least 2,000 BP until the 17th century in southernmost sites. Dwarf mangrove stands gradually replaced marshes as salinity increased. Cores from freshwater sites indicate that slough vegetation, characteristic of relatively long hydroperiods, dominated from about 2,500 BP until the 19th century. Vegetational changes during the Medieval Warm Period (~AD 800-1300) include maximum abundance of Chenopodiaceae/Amaranthaceae pollen, which may be correlated with more frequent droughts and fires. In the late part of the Little Ice Age (~AD 1500-late 1800s), tree-island taxa such as Myrica and Ilex became more abundant, indicating drier conditions. Assemblages from the last century show localized vegetational changes tied to water management practices, canal and road construction, and other human activities. Such data are critical for prediction of vegetational response to future changes in water management and agricultural practices in the system.

Key words: Everglades, Florida, pollenm Holocene