At the end of the last ice age, 15,000 years ago, the Americas had many species large mammals (Pleistocene megafauna) that were more diverse than those of the modern Serengeti. About that time, they quickly became extinct. There is much controversy about why animals such as big cats, elephants, horses, camels and ground sloths suddenly disappeared. Some scientists blame climate change, while others blame the arrival of human hunters. In the last few years, paleoecologists have developed a new way to investigate the population fluctuations of these extinct mammals: they count microscopic spores that were produced long ago, grew only on large amounts of dung, and are now preserved in lake sediments. The sudden disappearance of these spores in sediment cores is an excellent indicator of the disappearance of the Pleistocene megafauna. In this proposal, scientists will investigate the timing of the megafaunal population decline at sites in Panama, Brazil and Peru, and compare them with very detailed records of past climate change, and with the archaeological record. By doing so, scientists will be able to determine if climate change or the arrival of humans most likely caused the mass extinction.
The end of the last ice age was the most recent time when climates warmed almost as rapidly as under modern conditions, and there was huge instability in precipitation regimes. Investigating the potential link between extinction events and abrupt climate change has clear relevance to modern concerns. To observe which, if any, climate changes triggered population reductions or recoveries thousands of years ago, has repercussions for agricultural policy as well as conservation. Similarly, establishing whether the largest mammalian extinction event in the last 6 million years can be assigned to human actions is relevant to how we perceive our relationship to the natural world. Finally, the project will train students in paleoecology and produce materials for dissemination to large audiences.
