The koala

Somewhere in the high fork of a grey gum an animal the size of a small dog is asleep, as it will be for some twenty hours out of every day, eating almost nothing but the leaves within arm’s reach. The koala is the face this region has chosen for itself, and its existence turns on one narrow bargain. It eats the leaves of a particular handful of gum species and little else. That food is so poor in nourishment, so laced with oils and toxins, so armoured with indigestible fibre, that scarcely any other mammal on the continent will touch it. The koala gets away with it by doing as little as possible. It sleeps through most of the day, moves slowly, runs a frugal metabolism, and carries a gut full of microbes that ferment the leaves and disarm their poisons. It is a beautifully disciplined way of making a living, and it works for one reason above all: nothing else competes for the food.

For all its fame, the koala is a bit-player in the forest’s leaf economy. Far more eucalypt foliage goes to insects, in quantities no mammal comes close to, and it was largely against those insect armies that eucalypt leaves became so poisonous in the first place. The koala has merely learned to tolerate defences meant for someone else. So it is the forest’s emblem more than its main grazer, which makes what has happened to it all the more telling.

The bargain ties the koala absolutely to its trees. Not to eucalypts in general but, in practice, to its preferred feed species, growing thickly enough and close enough that an animal can pass between them without coming to the ground. A koala population therefore asks three things of a forest at once. It needs the right feed trees; it needs enough of them; and it needs connection, trees joined closely enough to be crossed in safety. It leans, too, on the big old veterans of the forest, which give shade, shelter and safe passage through the canopy. Take any one of those away and the bargain unravels. The modern landscape has taken all three. Across South-East Queensland, this coast included, the koala’s forests have been cleared for farms and suburbs, cut into fragments by roads, and left as islands too small or too far apart to hold the animals in them.

That is the thing to hold onto when you ask why the koala is in trouble. At bottom it is not the disease. It is the broken forest, and onto broken forest the other threats bite hardest: the traffic, the dogs, and above all a chlamydial infection that spreads through stressed, crowded populations and brings on blindness, infertility and death. The result is one of the most-studied and most-troubling wildlife declines in the country, right on this coast’s doorstep. Long-term work across the region has tracked, year on year, the grinding toll of vehicle strike, dog attack and lost habitat. Inside a couple of human generations the koala has gone from common to officially threatened, listed Endangered under national law in February 2022. This is not the first time we have pressed it hard. In the 1927 “Black August” open season alone, Queensland’s fur trade sold hundreds of thousands of koala skins.

And yet this coast is also pushing back, with a piece of science you would not expect: a vaccine, developed over more than a decade at the University of the Sunshine Coast, against the chlamydial disease. In a wild-population trial it cut deaths from the disease by nearly two-thirds, and in 2025 the national regulator granted it a minor-use permit for wider use, a permit rather than full registration. Consider what that involves. You must identify the strain, design the vaccine, then test it on a notoriously delicate wild animal that sleeps most of the day and bites when it wakes. It is a genuine feat, and a homegrown one. But a vaccine treats a single threat in the koala’s path and cannot manufacture forest. You cannot inoculate an animal against bulldozers and traffic. Read the koala for what it actually depends on and the answer is stubborn and plain. Save the trees, joined up, and you might save the koala; save the koala without the trees and you have saved very little.

Read it, finally, as an emblem in the full sense of the word, a stand-in for the whole cast it shares the gum forest with. The koala asleep in its fork does not itself need a hollow. The gliders and owls and cockatoos around it do, and cannot breed without one a century in the making. But the forest that must stay standing and joined up for the koala is the same forest those animals need. Keep it whole for the emblem and you keep it for everything behind the emblem.