Koalas live in eucalyptus woodland and forest ecosystems along the eastern and southeastern coast of Australia. These ecosystems range from tall coastal forests to drier inland woodlands, but they share one defining feature: an abundance of eucalyptus trees, which provide koalas with nearly everything they need to survive, including food, shelter, and water.
Eucalyptus Forests and Woodlands
The ecosystems koalas depend on are built around eucalyptus trees. Koalas feed almost exclusively on a handful of preferred species, and the presence or absence of those trees determines whether an area can support a koala population at all. Key food trees include tallowwood, forest red gum, ribbon gum, swamp mahogany, and river red gum. Secondary species like yellow box, black box, and various stringybarks round out the diet in different regions.
Not all eucalyptus forests are equal. Population surveys have recorded densities as high as about 0.4 koalas per hectare in forest red gum and bloodwood woodland, while some vegetation types support no koalas at all. Mixed eucalypt woodland, which can cover large stretches of landscape, tends to support moderate densities. The difference comes down to the nutritional quality of the leaves, how much water they contain, and the concentration of natural toxins the trees produce to deter herbivores.
Where These Ecosystems Exist
Koala habitat stretches across Queensland, New South Wales, Victoria, South Australia, and the Australian Capital Territory. Within that range, koalas occupy everything from subtropical coastal forests in Queensland to temperate woodlands in Victoria and semi-arid floodplain forests along inland rivers. They’ve been observed from as low as 15 meters below sea level near Lismore in New South Wales to as high as 1,500 meters in the Nandewar ranges in northern New South Wales.
Elevation matters because it changes the chemistry of the leaves. Trees growing at higher elevations tend to have lower concentrations of key nutrients like sodium and higher levels of defensive plant compounds that make the foliage less palatable. This is why koala abundance drops at higher altitudes even when eucalyptus trees are present.
Climate Conditions That Define Koala Habitat
Habitat suitability models show that koalas do best where mean maximum summer temperatures sit between 23 and 26°C and annual rainfall falls between 700 and 1,500 millimeters. That rainfall range supports the moisture content of eucalyptus leaves, which is critical because koalas get most of their water from the foliage they eat rather than from drinking.
Koalas are arboreal marsupials largely dependent on “pre-formed” dietary water, meaning the water already inside leaves. The moisture content of eucalyptus foliage varies enormously. In tropical northeastern Australia, some species hold more than twice as much water as dry matter. In semi-arid floodplain woodlands, that figure can drop to just 75% of the dry weight. During hot conditions, koalas need more water to cool themselves through sweating and panting. If leaf moisture is too low, they may stop eating entirely. During extreme heat events, koalas have been known to starve to death.
Leaf moisture also fluctuates throughout the day. Koalas may prefer tree species that maintain a higher minimum moisture level across the full 24-hour cycle, giving them a more reliable water source even during the hottest part of the day. During drought, the normal overnight recovery of leaf moisture is disrupted, making conditions even harder.
Deep gullies, cliffs, caves, and patches of dense vegetation can create cooler microclimates that act as refuges during heat waves. Ecosystems with these features, along with perennial water sources that keep leaf moisture high, are especially important for long-term koala survival.
How Habitat Fragmentation Changes the Ecosystem
Koala ecosystems across eastern Australia have been significantly fragmented by land clearing for agriculture and urban development. This fragmentation doesn’t just shrink the total area of habitat. It changes how koalas move through their environment. When the connections between patches of forest are broken, koalas are forced to make longer, more direct movements across open ground to reach the next cluster of food trees. They also end up using more scattered “core patches” within their home range instead of moving fluidly through continuous forest.
Time spent on the ground is dangerous. Wild dogs, including dingoes and dingo-domestic dog hybrids, are significant predators. Genetic sampling of koala remains in peri-urban areas of northeastern Australia found canine DNA on 92% of predation victims, and almost all of it belonged to wild dogs rather than domestic pets. Vehicle collisions are another major threat in fragmented landscapes. Restoring or protecting connecting corridors of eucalyptus between isolated patches is one of the most effective ways to reduce these risks.
Current Conservation Status
The combined koala populations of Queensland, New South Wales, and the Australian Capital Territory were listed as endangered under federal environmental law in February 2022. The key threats are habitat loss, fragmentation, disease, vehicle strikes, dog predation, and climate change. Rising temperatures and declining winter and spring rainfall across the koala’s range are predicted to increase the frequency and intensity of heat stress, pushing many existing ecosystems beyond the conditions koalas can tolerate.