Why Koala Populations Are in Decline

Understand the threats to this iconic marsupial, and learn how you can help.

koala on tree branch

 Raimund Linke / Getty Images

Koalas aren’t officially endangered, but their status is unstable and population numbers are dropping. Koalas are endemic to Australia, meaning that's the only place where the marsupials exist in the wild. Australia was once home to millions of koalas, but the Australian Koala Foundation says koalas are now "functionally extinct." The group estimates there are no more than 80,000 koalas left in the wild in Australia.

Various groups have different categorizations for the iconic marsupial. The International Union of Conservation of Nature (IUCN) Red List of Endangered Species lists koalas as "vulnerable" with decreasing numbers. In 2000, the koala was listed as “threatened” under the U.S. Endangered Species Act by the U.S. Fish and Wildlife Service.

In 2012, the koala was listed as “vulnerable” in Queensland, New South Wales, and the Australian Capital Territory under Australia’s Environment Protection and Biodiversity Conservation Act. The WWF-Australia has warned that koalas could be extinct in New South Wales, Australia’s most populous state, by 2050.

Why are koalas in decline illustrated gif

Treehugger / Alex Dos Diaz


Koalas are threatened by decreasing loss of habitat due to tree clearing. They are also impacted by other factors including disease, climate change, and devastating bushfires.

Habitat Loss

Koalas lose their homes due to excessive tree clearing for agriculture, housing, roads, and mining. Most tree clearing is performed in Australia to create pasture for livestock, according to the WWF-Australia. Agricultural tree clearing was put on hold in the late 1990s and early 2000s after New South Wales and Queensland instituted bans on the practice. However, recent legislative changes have made it easier for landowners to again clear trees for agricultural use.

When koalas lose their habitat, they are forced to come out of the trees and onto the ground so they can move to another location, reports the WWF-Australia. This makes them more vulnerable to being attacked by dogs or cats or hit by vehicles when they wander out into the road. They also face more competition for territory and food as their habitat shrinks.


Devastating bushfires started spreading across eastern and western Australia in October 2019, ravaging many parts of the continent. By the time they were contained in February 2020, the fires had destroyed more than 2,400 homes and about 13.3 million acres (5.4 million hectacres) in New South Wales alone.

koalas nurse with bottles after Australian bushfires
Rescued koala joeys are fed by volunteers after Australian bushfires in early 2020. Lisa Maree Williams / Getty Images 

An estimated 6,382 koalas were killed across New South Wales during those wildfires, according to an updated report from the International Fund for Animal Welfare. That’s 15% of the koala population in the area, which researchers say is a conservative estimate. The marsupials died from burns, smoke inhalation, starvation, and dehydration.


Koalas are seriously threatened by chlamydia. The bacterial infection is primarily transmitted sexually between adults, but it also can be spread by close contact between mother and babies, called joeys. Chlamydia can lead to blindness, pneumonia, severe urinary tract infections, and infertility. Chlamydia symptoms include sore eyes, chest infections, and a wet, dirty tail area, according to the Australian Koala Foundation.

Chlamydia can infect 100 percent of koala populations. However, in 2019 on Kangaroo Island, researchers from the University of Adelaide said they found what could be the last Australian koalas without chlamydia, according to a 2019 study published in the journal Nature Scientific Reports.

"The impact of chlamydia on populations of koalas in parts of Australia is devastating, with high levels of severe disease and death, and common infertility," lead author Jessica Fabijan said in a statement. "This last chlamydia-free population holds significant importance as insurance for the future of the species. We may need our Kangaroo Island koalas to re-populate other declining populations."

In addition to chlamydia, koalas can also suffer from several cancers such as skin cancer and leukemia.

Climate Crisis

With the climate crisis, increasing levels of carbon dioxide (CO2) in the air are also a threat to koalas. Rising CO2 levels reduce the nutrient quality of eucalyptus leaves — the koala’s main source of food. Plants often grow faster with increased CO2 levels in the atmosphere, but this rapid growth often results in reduced protein levels and increased tannins in plant leaves, according to the IUCN. 

Eating the nutrient-poor leaves can lead to malnutrition and even starvation for the koalas. Often, the marsupials will leave their trees in search of better leaves. Coming down to ground level puts them at risk of encountering predators or being hit by vehicles in the road.

More frequent and severe droughts, as well as extremely high temperatures, have also been linked to the climate crisis. These weather threats force koalas to come down from trees to look for water or new habitats. Again, they are vulnerable to traffic and predators.

What We Can Do 

There has been a long history of conservation efforts for the koala, in part because of its iconic status. Efforts include land management, relocation, monitoring, threat management, and lots of research. There are many captive breeding programs in Australia and throughout the world.

People can donate to the WWF or send messages to politicians urging them to stop excessive tree clearing. You also can donate, adopt a koala (virtually), help fundraise, or purchase items to help koalas through the Australian Koala Foundation.

During the 2019-2020 bushfires, more than 30 koalas were rescued and brought to the Port Macquarie Koala Hospital in New South Wales for help. After raising more than $7.9 million initially to install drinking stations in burned-out areas across the country, the hospital plans to create a koala breeding program with the extra funds. The hospital is still accepting donations for the project.