Researchers have discovered that the arrival of humans in Australia was likely the driver of intense changes to the region, which led to the extinction of Australia’s 55 giant herbivores such as the 3-ton rhinoceros wombat and giant kangaroo, LiveScience.com reported on Thursday.
Also there was a rapid shift in vegetation across Australia soon after the beasts disappeared. Once rainforest separated by areas of open grassland, it was soon smothered by eucalypt forest, according to the team from the University of Tasmania in Australia.
"Quite soon after people turned up, there were big changes in the way everything looked and what plants and animals you would have seen,” said a researcher.
The scientists analyzed sedimentary layers in two samples to figure out how populations of Australia's giant herbivores changed and what their effect was on the landscape. The first sample dates back to between 130,000 and 24,000 years ago and the second reaches from 53,000 to 3,000 years ago.
As a result, they found a severe drop-off in fungal spores that is dependent on the digestive systems of herbivores to survive around 41,000 years ago, suggesting a drastic decrease in certain plant-eating animals. Then, a few hundred years later, records showed a big increase in the amount of charcoal in the ground, suggesting a dramatic rise in the number of fires.
Because large animals reproduce slowly, it would have been easy for a small population of humans to hunt enough that the populations couldn't rebound, they suggest.
And new type of pollen or plant species appeared after the fires. The ground seems to have been taken over by a new type of plants: grassy ones on the forest floor and an overhang of eucalyptus plants.
"Both climate and vegetation had been stable for the previous five millennia," said the researchers. “Climate change could not have been responsible for the landscape change of Australia.”
"It's the big animals declining that causes the increase in charcoal and the change in vegetation that we see. It basically changed everything,” they stressed.
Such drastic landscape-changing die-offs could happen in modern times, researchers say.
“It could happen to large herbivores such as elephants, giraffes and rhinoceros in Africa and the whole landscape’s structure would be gone.”