According to a new study led by Dr. Catalina Pimiento of the University of Zurich, big marine life may be more vulnerable to changes in the climate than previously known.
The study – "Pliocene marine megafauna extinction and its impact on functional diversity" – looked at fossils from large marine mammals, sea birds, sharks, and other large coastal marine life over a period of about five million years, from the Pliocene up until the end of the last ice age. The results?
“We were able to show that around a third of marine megafauna disappeared about three to two million years ago. Therefore, the marine megafaunal communities that humans inherited were already altered and functioning at a diminished diversity," Pimiento said. Marine mammals were hardest hit, with more than half of the Pliocene-era species disappearing.
“This study shows that marine megafauna were far more vulnerable to global environmental changes in the recent geological past than had previously been assumed," Pimiento said. “Our models have demonstrated that warm-blooded animals in particular were more likely to become extinct."
In addition to the casualties among marine mammals, 43 percent of sea turtle species, 35 percent of sea birds and nine percent of sharks, including the massive Carcharocles Megalodon, went extinct. Diversity levels did not recover after this exctinction event, though new and familiar animals would emerge – the storm petrel, the polar bear and the yellow-eyed penguin, among others.
Dr. Pimiento’s team estimated that these extinctions took out about 17 percent of the preexisting ecological functions in coastal ecosystems and changed a further 21 percent, creating significant changes in predator-prey relationships. The period of functional and species diversity loss coincided with the destruction of coastal habitat due to violent fluctuations in sea level, a function of the rapid glaciation at the beginning of the Pliestocene.
While the extinctions occurred in parallel with falling ocean temperatures and sea levels, the authors warned that they provide a cautionary tale for modern, warming times: large marine species like whales and seals are still highly vulnerable to human influences.