March 15, 2013
Habitat Changes Caused Turtle Collapse 71 Million Years Ago
Lee Rannals for redOrbit.com — Your Universe Online
About 71-million-years ago, turtles disappeared from Alberta's Drumheller area, and scientists have been blaming dramatic climate change as the culprit. Now, a new theory published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology suggests the real reason was because of habitat changes.
Researchers at the University of Calgary studying ancient soil in Red Deer River valley say it was the loss of the wetlands that led to the vanishing of turtles 71-million-years-ago. A drastic climate change caused the wetlands to dry up and the warm humid climate to become interrupted five-million-years before. However, the team's research indicates that the disappearance of the turtles came before the climate cooled.
"This was a time of change in Alberta, the wetlands disappeared as the inland sea retreated and the climate cooled," says Annie Quinney, a former master's student in the Department of Geoscience who led the study.
She says the big surprise in the study is that some animals appeared to be more sensitive to habitat disturbances than to climate changes. "Therefore, even if climatic conditions are 'ideal,' turtles may disappear or may not recover unless habitats are just right," says Quinney.
The team studied ancient soils preserved in the rocks in the river valley near Drumheller that were deposited between 72 and 67 million years ago. After this, they recorded information about the past climate and environments.
The researchers then calculated precipitation and temperature levels over a five-million-year period and found that during that time, temperature and precipitation dropped over a few thousand years.
"By studying the structure and chemistry of ancient soils, we were able to estimate the ancient temperature and rainfall that prevailed when those soils formed millions of years ago," says Quinney, who is now completing a PhD at Monash University in Australia on a full scholarship.
Studying ancient climate change helps researchers understand the impact sudden heating and cooling may have had on plants and animals. UCLA geoscientists and colleagues said in 2011 that fossilized mollusks from 3.5 million years ago may hold clues about the long-term effects of Earth's current levels of atmospheric carbon dioxide.
"Our data from the early Pliocene, when carbon dioxide levels remained close to modern levels for thousands of years, may indicate how warm the planet will eventually become if carbon dioxide levels are stabilized at the current value of 400 parts per million," said Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.