Washington: Climate change eight million years ago radically altered the vegetative set up in northern Pakistan, resulting in the extinction of most species as they could not adapt to the new ecosystem, said a long-term study of mammal fossils spanning a five-million-year period.
The study said that many of giraffe, rhino and elephant species, along with a multitude of rodents, bush pigs, horses, antelope and apes once roamed northern Pakistan.
Michigan University Paleoecologist Catherine Badgley said, "The climate is going to produce changes in ecological structure of all sorts of plants and animals around the world, now as in the past."
Badgley is part of an interdisciplinary team of geologists and paleontologists that has been studying the fossil-rich Sivalik sedimentary rocks in northern Pakistan for more than 30 years, reports IANS.
Sivalik 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 one million years ago, reports IANS.
About eight 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 teeth provide evidence of the animals' diets, revealing whether they switched to eating the newly abundant grasses when their favoured fruits and broad-leafed plants were no longer available.
By the time that savannah was the dominant vegetation, most herbivorous mammals in the area subsisted mainly on grass. The overall effect was a significant decline in the diversity of mammals in the area.
"This is the kind of study you can only do after you've been working in a place with a big team for 25 years or more, because you need all the other basic data to be thoroughly resolved before you can even start to address the kinds of questions in this work," Badgley said.
These findings were published online in the Proceedings of the National Academy of Sciences.