Fire — the force that draws the boundaries

The instinct is to file fire under disaster, an accident that overtakes the bush and that it pulls through in spite of itself. Across most of the Sunshine Coast the instinct has it backwards. Fire is not something that happens to this vegetation so much as something the vegetation does, wound as deep into these plants as their need for rain or light, and strip it out and a great deal of what grows here would go with it. The eucalypt supplies the fire that burns it. Its leaves are steeped in volatile oils, it drops bark and twig into a dry mattress of litter that rots far too slowly to clear itself, and its ribbon bark hangs in loose tresses ready to lift a ground fire up into the canopy. A tree that assembles its own pyre is not being careless. Flame kills the faster, thinner-skinned seedlings that would otherwise overtop and shade it out, and hands the cleared, sunlit, ash-dressed floor to the tree already equipped to come through the heat.

Fuelling a fire only pays if you can outlive it, and the eucalypt is built to. Under a bark thick enough to insulate the living tissue from a passing burn, epicormic buds lie sealed inside the trunk itself; within weeks of a blaze that has scorched a tree to a bare black pole they break out through the char in a green stubble of fresh leaves, one of the odder and more heartening sights in the Australian bush. Many shrubs keep the same insurance underground, in a lignotuber — a swollen woody crown, part fuel-tank and part bud-bank, that throws up new stems the moment the flames have passed.

Others go further and stake the next generation on the burn itself. The wallum’s banksias, hakeas and grevilleas clamp their seed inside hard woody cases and will surrender it to nothing cooler than fire, so it drops onto a seedbed swept clear of rivals and dressed in ash at the moment its odds are best. A whole guild of understorey plants holds its seed dormant in the soil until it tastes the chemistry of smoke, a signal that reads, in effect, the ground has just been cleared. And the grass-trees — the Xanthorrhoea that everyone knows on sight and almost nobody can name — will send up their tallest flower spike in the season after a fire, as though the smoke had thrown a switch.

None of this makes every fire the same fire. What a given burn does turns on three things at once. How much fuel has banked up, the weather driving it, and the shape of the ground it runs across. Fire scientists call the combination the fire-behaviour triangle. A stand left unburnt for twenty years, its litter deep and its understorey grown tall and knitted together, will burn far hotter and climb far higher than the same ground two years on from a fire. A gentle autumn burn and a summer holocaust can share a name and almost nothing else.

Fire’s larger work runs in two directions this account can only point toward. It holds the frontier between rainforest and eucalypt forest, deciding at the green edge which of the two keeps the ground. Laid unevenly across the country, it also stitches the land into a shifting patchwork, so there is never one correct fire, only the flame each stretch of the gradient is built around. For reading the country, all of it comes down to one reversal. Fire here is not the intrusion; its absence is. Hold the burns off a fire-built landscape and you do not keep it safe and you do not keep it still — you quietly convert it into something else, one unburnt decade at a time.