New research suggests that low atmospheric oxygen levels had already increased extinction rates prior to the massive animal and plant extinctions 251 million years ago. Furthermore, reduced oxygen likely contributed to the protracted recovery from the catastrophic event.
Based on predicted oxygen levels in the late Permian and early Triassic periods–the timeframe spanning the great extinctions–Raymond Huey and Peter Ward at the University of Washington simulated on a computer the combined effects of reduced oxygen and topography on a set of hypothetical species representative of the period.
The scientists, whose work is supported by the National Science Foundation (NSF), published their findings in the April 15 issue of the journal Science.
As atmospheric oxygen decreased in the late Permian period, hypoxia, or insufficient oxygen in bodily tissue, would have become an undeniable problem for Earth’s terrestrial species. Huey and Ward predicted that eventually, because oxygen levels decrease as altitude increases, only land near sea level would have been habitable on the relatively new supercontinent of Pangaea. As a result of this so-called “altitudinal compression,” even modestly high mountains would have represented insurmountable barriers that prevented intermingling and reproduction between nearby populations.
These results could force paleontologists to re-evaluate the accepted notion that Pangaea was like a “superhighway” for species movement, as its mountain ranges may have impeded movement and drastically affected species development.
William Zamer, a manager in NSF’s program for Integrative and Organismal Biology said, “Huey and Ward have produced a novel and insightful study linking the effects of a low-oxygen atmosphere with the possible biogeographic and evolutionary consequences on terrestrial animals during the Permian extinction.”