The koala is one of Australia’s most recognizable fluffy icons. It may seem as if these animals should be sitting peacefully on every other eucalyptus tree, philosophically watching tourists pass by. Alas, reality is far less serene. In several regions of the country, koalas have already been officially recognized as a species at risk of extinction. But a new study has shown that today’s crisis is far from the first in their history. And, apparently, the ancient population decline was not caused by humans at all.
For a long time, scientists believed that the largest drop in koala numbers happened about 40,000 years ago — after humans had already arrived in Australia. This version fit neatly with the idea that the continent’s first inhabitants may have affected local wildlife. But genome analysis changed the picture. It turned out that the mass decline began almost 60,000 years earlier.
The cause was entirely natural — sharp climate changes. During the Pleistocene, Australia experienced a series of cold and dry periods. Forests gradually shrank, familiar habitats disappeared, and koala populations became separated. The western branch became extinct about 28,000 years ago, while eastern koalas managed to survive the unfavorable period in a small forest refuge. When the climate became warmer and wetter again about 17,000 years ago, forests began to return, and koalas expanded their range along with them.
Today, the main threat to koalas is once again the disappearance of forests. Added to this are disease, the consequences of past hunting, bushfires, collisions with cars, and attacks by feral dogs. But there is also good news. Genetic analysis showed that most populations have only recently begun to lose genetic diversity. This means that with timely forest protection and habitat restoration, the chances of stopping the decline in numbers and saving the species remain quite high.
