Paperbark swamp and blackwater sedgeland

Follow the water downhill far enough and the gradient runs out of slope. The tea-dark water off the wallum, and the run-off from the ridges above, drains into the lowest, flattest, wettest ground there is, and gathers, and stands — too flat to run off, too wet to drain away. Where water sits like this, a particular and wonderful kind of forest takes hold: the paperbark swamp.

The paperbark is unmistakable once you know it. Its trademark is the bark — thick, soft, spongy, pale, peeling off the trunk in papery sheets like the pages of a sodden old book — and the great swamp-former here, the broad-leaved paperbark, gathers into dense, dim, pale-trunked stands in the wettest hollows, often with its boots underwater for months on end. Living with wet feet is nearly as hard a trick for a tree as living in salt, and for the same reason: waterlogged soil is airless soil, and roots need to breathe. The paperbark is built for a world that floods one season and parches the next, which is precisely the world the lowlands offer.

Because the thing that rules a swamp is not how high the ground is, nor how rich, but water — and above all how long each patch of it stays wet. That one number sorts the plants into bands and times the animals to their seasons, and the flood that fills the swamp and the dry that empties it are not interruptions to its life but the engine of it. When the rains come, and on this coast they come hard, the whole system detonates: the paperbarks smother themselves in creamy, nectar-dripping spikes and the lorikeets and flying-foxes pour in; the frogs erupt into a chorus loud enough to carry across the paddocks; the fish fan out over the drowned flats to feed and breed. Then the dry returns and the boom collapses back to the last permanent pools, and the nomad waterbirds lift off to find wherever the next rain has fallen.

And while it is at all of this, the swamp quietly does the work we are least willing to pay for. It swallows a flood — spreading the surge across a wide flat and letting it go slowly, shaving the dangerous peak off the water downstream. It cleans what runs through it, the sedges and paperbark roots combing out sediment and nutrient so that what seeps on is markedly clearer than what arrived. It banks carbon, piling up undecayed litter as peat in the airless mud. For two centuries we read all this as mosquito-ridden waste and drained it for cane and pasture, which is how the freshwater wetlands became among the most thoroughly destroyed country on the coast — and how we learned, too late and at great expense, that the swamp was the flood mitigation we then paid engineers to rebuild worse. It is no wasteland. It is closer to the coast’s hardest-working and least-thanked organ, and its boom-and-bust pulse is not a fault to engineer out with a drain and a weir but the very rhythm the frogs and fish and waterbirds breed and feed by. A wetland held forever at one fixed level is one with its engine switched off.