Fire — the force that draws the boundaries

The instinct is to file fire under disaster — an accident that befalls the bush now and then and that the bush survives in spite of itself. Across most of the Sunshine Coast that instinct is almost exactly wrong. Fire is one of the things the vegetation is made of, as much a part of how these plants live as rain or sunlight, and a great deal of what grows here would simply vanish without it. The eucalypt is not fire’s victim; with its oily leaves, its heaps of slow-rotting litter and its wicking bark, it is closer to an arsonist, making itself flammable on purpose because fire clears away its softer competitors and leaves it holding the ground.

Fire’s deepest work, though, is drawing a line. The rainforest and the eucalypt forest want opposite things: one promotes fire and thrives on it, the other defends itself by staying too wet to burn, keeping its floor dark and damp so a fire approaching from the dry forest outside runs out of fuel at the green wall. So the boundary between them, which looks fixed on a map, is nothing of the sort. Burn often and the rainforest stays penned in the gullies; withdraw the fire for long enough and it creeps out, shades the grass away, and quietly smothers the eucalypts in the gloom of their own usurped forest. The rainforest never has to defeat the gums. It only needs the fires to stop, and time.

And there is no single right amount of fire, because the coast is not one place. The rainforest wants none; the wet forests want the occasional burn; the dry foothill woodlands want a light fire every few years; and the wallum heath, hungriest of all, positively depends on it — many of its banksias and peas lock their seed in hard woody fruit and hand it over only to a fire’s heat, dropping it onto a cleared, ash-fertilised bed with the competition burnt away. Leave that heath unburnt too long and it stops being a wildflower garden; it grows leggy and tired and the diversity drains out of it. Match the fire to the ground and you keep every world along the gradient; get it wrong in either direction and you lose one.

What that means for reading the country is that the question is never simply was there fire but what fire, and how often. A patch of straight gums over open grass has been lightly and recently burnt; a wall of green rainforest in a gully is fire’s refuge; a heath blazing with spring flowers is answering a burn with everything it has. But where woody scrub is closing over what was open woodland, or rainforest pioneers are stealing into the eucalypts, you are looking at country that has gone too long without the flame it was built around — a very old conversation, lapsed.