The landscape of present-day Australia once was home to 500-pound kangaroos, tapirs as big as horses, giant wombat-like creatures and 8-foot turtles.
Now new research indicates that climate change could have been the cause of these large species' extinction some 30,000 years ago.
According to a study published in the journal Paleobiology, as weather patterns in the region changed, the land started to dry out and affect the animals' food supply. Many were unable to adapt, and entire species — known as megafauna — died out as a result.
“In general, species have three options with any sort of change in climate: They can adapt, they can move or they can go extinct. Unfortunately, this was a scenario where the climate was changing at a rate that was much slower than what's happening today — and yet, the animals went extinct,” said Larisa DeSantis, an assistant professor with Vanderbilt University and author of the study.
DeSantis and her colleagues came to this conclusion by studying fossilized megafauna teeth from Cuddie Springs in southeastern Australia. The oxygen and carbon isotopes present in the remains provided them with records of temperature and humidity levels during the period. This is a technique that scientists have tested out on modern-day kangaroos, as well, and have discovered that the chemical composition of the teeth is a good proxy to judge humidity.
“This makes them ideally suited for tracking changes in aridity over time,” said DeSantis.
They were also able to draw conclusions about what the megafauna were eating by examining small scratches on the teeth, and realized that as the climate got drier and drier, the animals were shifting away from their regular plant resources. The inability to find adequate food, as well as the lack of water, likely contributed to the extinction. Moving away from the region was also difficult because in Australia, cooler climates could be found only high up in the mountains, in areas that the large animals couldn't access easily.
“What we saw was this increase in aridity and decrease in resources. If the landscape is getting drier, water availability is also more limited and the water content in plants is lower. So you have these animals having to compete with one another for fewer resources — there are these negative consequences, which makes the animals more stressed,” she explained.
The findings of the study are part of a much larger, fiercer debate within the scientific community over the megafauna extinction. Many researchers attribute the extinction to human causes — that is, they believe the animals were hunted and deprived of habitat until they died out.
While DeSantis does not rule out the possibility that human activity might have contributed, she pointed out that there's no empirical evidence that they did.
“And if it's climate that played a role, whether a small role or a decisive one, that suggests we seriously need to think of the consequences of current climate change,” she added.
“This new study, based on hard evidence, makes it clear that changes in late Pleistocene climate had a major impact on the late Pleistocene megafauna of Australia, adding even more evidence to challenge the imaginative a priori assumption that 'blitzkrieg' by early humans caused the extinction of this continent's lost megafauna,” said Michael Archer, a paleontologist with the University of New South Wales.
Scientists still have a lot to learn about megafauna, DeSantis said, including the intricacies of their ecology and biology.
“Some animals might have been particularly vulnerable to climate change because of their biology and others less so. It's really important that we study them to get a better understanding of vulnerabilities, and what characteristics make certain animals more or less resilient,” she added.
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.