Stratigraphic palynological analyses of four late Quaternary deposits comprise a landscape-level study of the patterns and processes of megafaunal extinction in southeastern New York State. Distinctive spores of the dung fungus Sporormiella are used as a proxy for megafaunal biomass, and charcoal particle analysis as a proxy for fire history. A decline in spore values at all sites is closely followed by a stratigraphic charcoal rise. It is inferred that the regional collapse of a megaherbivory regime was followed by landscape transformation by humans. Correlation with the pollen stratigraphy indicates these developments began many centuries in advance of the Younger Dryas climatic reversal at the end of the Pleistocene. However, throughout the region, the latest bone collagen dates for Mammut are considerably later, suggesting that megaherbivores lasted until the beginning of the Younger Dryas, well after initial population collapse. This evidence is consistent with the interpretation that rapid overkill on the part of humans initiated the extinction process. Landscape transformation and climate change then may have contributed to a cascade of effects that culminated in the demise of all the largest members of North America's mammal fauna.