Amazing Planet: Koalas' biggest threat are humans

Koala "bears" are a marsupial that rear their young in a pouch — and therefore, are not actually bears — that evolved over 25 million years ago.

A very distant relative of the wombat, no other animal on earth comes close to them and they're even classified into their own family, called Phascolarctidae. These loners are also very territorial. 

One of the most iconic animals on the planet, the universal symbol for all that is cute and fluffy — and lazy — has extremely powerful claws with three fingers and two thumbs for extra grip. These paws allow koalas to easily scale and make a home in towering eucalyptus trees that dominate Australian forests.

The animal is raised in its mother's pouch and sleeps up to 22 hours a day. Koalas get so tired because they spend their waking life feasting on toxic eucalyptus leaves that would kill most mammals. They eat up to one kilogram (2.2 pounds) a day due to the low nutritional value of the leaves, and also to satisfy their thirst.

Koalas are also extremely fussy. The will eat just 50 varieties of the more than 800 eucalyptus species in Australia.

These trees can only be found in Australia's relatively forested east and southeast coast. The problem is, when forests burn or are cut down, Australia's furriest mascot has nowhere to go.

Wildfires and chlamydia threaten koalas

Back in 1788 when the British invaded Australia, as many as 10 million koalas were said to inhabit the country. That number has now dropped to 50,000 by some estimates.

Since European colonization, millions of koalas died at the hands of hunters who prized their furs. More recently, koala populations are threatened as habits are cleared for development. 

If that's not bad enough, chlamydia, a sexually transmitted disease, is rampant through the population. It can not only cause blindness, but infertility.

But global heating is the animal's greatest threat. Drought and extreme heat are reducing the water and nutrition content of the koala's pure leaf diet. And wildfires worsened by climate change have already destroyed fast swathes of their habitat.

Scenes of blackened, burning koalas fleeing the Black Summer fires that engulfed eastern Australia in 2019-2020 helped inspire politicians to raise the conservation status of koalas from vulnerable to be endangered.

Yet koala numbers declined 30% between 2018 and 2021. In the state of New South Wales, Australia's most popular animal will likely be extinct by 2050 without urgent intervention.  As populations become more isolated, a reported lack of genetic diversity also limits their ability to adapt.

Could koalas be saved?

While the koala population is struggling in the hotter north, the marsupial is said to flourish in cooler climates and some populations are stable in the southern state of Victoria — and more genetically diverse.

The koalas are also a few kilos bigger on average and are also fluffier with more fur.

Though they weigh up to 14 kilograms in the south, the critters are half the size of the "giant" koalas that roamed Australia until becoming extinct around 50,000 years ago.

The koala population in Victoria is around 24,000, according to one estimate and has the potential to grow. But, as ever, continued deforestation means its habitat limit has been reached — for now.

Edited by: Jennifer Collins