Wet is deadly, new extinction study says

CANBERRA - Australian-led research has found that major increases in environmental moisture occurred just before mass extinctions of large or giant animal species around 11,000-15,000 years ago.

According to the University of Adelaide's Australian Center for Ancient DNA, persistent moisture - which was caused by melting permafrost at the end of the last ice age - contributed to grasslands becoming boggy peatlands.

Using more than 500 radiocarbon-dated bones from animals such as bison, horses and llamas, the team was able to uncover the role that environment moisture played in the extinction of larger than human animals scientists describe as "megafaunal".

ACAD's director, Alan Cooper, says in a university news release that analysis of the fossils showed that extinctions occurred "just before" a number of species went extinct, suggesting some species were unable to adjust to the changed environmental conditions.

"We didn't expect to find such clear signals of moisture increases occurring so widely across all of Europe, Siberia and the Americas. The timing varied between regions, but matches the collapse of glaciers and permafrost and occurs just before most species go extinct," Cooper says.

Co-researcher Matthew Wooller of the University of Alaska Fairbanks says that while climate occurred on different continents at different times, "they all showed that moisture increased massively just before extinction".

"The really elegant feature of this study is that it produces direct evidence from the fossils themselves these extinct creatures are informing us about the climate they experienced leading up to their own extinctions," he says.

Lead author Tim Rabanus-Wallace from the University of Adelaide says that with the changed conditions, the food sources for a number of species were wiped out, meaning they did not stand a chance of surviving the environmental shift.

"Grassland megafauna were critical to the food chains. They acted like giant pumps that shifted nutrients around the landscape," Rabanus-Wallace says.

"When the moisture influx pushed forests and tundras to replace the grasslands, the ecosystem collapsed and took many of the megafauna with it."

Xinhua