ANN ARBOR, Mich.---Two species of giraffe, several rhinos and five elephant relatives, along with multitudes of rodents, bush pigs, horses, antelope and apes, once inhabited what is now northern Pakistan.
But when climate shifted dramatically there some 8 million years ago, precipitating a major change in vegetation, most species became locally extinct rather than adapting to the new ecosystem, according to an extensive, long-term study of mammal fossils spanning a 5-million-year period.
Results of the study, by University of Michigan paleoecologist Catherine Badgley and coworkers, are scheduled to be published online in the Proceedings of the National Academy of Sciences the week of Aug. 18.
The work has value not only in reconstructing Earth's past, but also for understanding what may lie ahead if current climate trends continue, Badgley said. "Climate is going to produce changes in ecological structure of all sorts of plants and animals around the world, now as in the past. The fossil record can help us understand how much---or how little---climate change is necessary to produce changes in ecosystems."
Badgley is part of an interdisciplinary team of geologists and paleontologists that has been studying the fossil-rich Siwalik sedimentary rocks in northern Pakistan for more than 30 years. The Siwalik Group of sediments contains one of the world's most complete and best-studied fossil records of mammals, chronicling in a two-mile-thick deposit of rock the mammals that roamed the area from 18 to 1 million years ago. About 8 million years ago, the local climate became drier, and the prevailing vegetation changed from tropical forests and woodland to a savannah similar to that found in parts of Africa today.
What happened next can be reconstructed from the chemistry and wear of the teeth of the plant-eating mammals, as well as the longevity of each species during the period when vegetation was changing. The tee
|Contact: Nancy Ross-Flanigan|
University of Michigan