The unglaciated Southeast is of conservation concern owing to its high biodiversity, including high endemism, in an increasingly fragmented landscape highly vulnerable to global climate change. Understanding the environmental and ecological history of the region can provide valuable context and perspective by helping assess biotic vulnerability and resilience to environmental change, and guiding managers to allocate resources most effectively in the face of both short- and long-term threats. We review the climatic and ecological history of the Southeast over the past 30,000 years, drawing on both published studies and our recent work on sites in the region.
Physical, geochemical, and paleontological proxies, as well as climate models, indicate that the entire Southeast has undergone substantial changes in temperature and hydroclimate over the past 30,000 years. These changes include both gradual and rapid changes, not only during the last glacial-to-interglacial transition, but also the Holocene. No part of the region has been ‘climatically stable’ during this time period, though magnitudes and rates of change have varied spatially and temporally.
Results/Conclusions
Vegetation throughout the region has changed in composition and structure since the last glacial maximum. Glacial-age forests and woodlands dominated by boreal and north-temperate conifers occupied the Ozark and Interior Plateaus, the southern Appalachians, and the Atlantic Coastal Plain. The Mississippi Embayment was dominated by an extinct Picea, accompanied by temperate hardwoods. Northern Florida was occupied by Quercus-Carya forest; peninsular Florida was Quercus scrub, with Pinus forest arising in wet periods. The glacial-to-interglacial transition was characterized by widespread, major vegetational changes, often comprising increases in Quercus and mesic hardwoods. Pinus-dominated forests did not arise until the past 6000 years. Pre-European vegetational configurations and fire regimes developed across both highlands and Coastal Plain in the past 1500 to 3000 years.
The dynamic environmental and ecological history of the Southeast seems paradoxical in view of the region’s high biodiversity. The region clearly experienced major vegetational changes, as well as glacial-age invasion by many species from the North. Plants and animals of the region have survived extensive environmental and ecological changes, suggesting that rather than being fragile, the southeastern biota have unexplored capacity to endure and adapt to change. Better understanding of that capacity will be a valuable addition to the conservation toolkit.