The Noosa Everglades (Upper Noosa River)

Put a canoe on the upper Noosa River, above the broad, shallow sheet of Lake Cootharaba, and paddle north into the Cooloola section of Great Sandy National Park, and the river slows almost to a standstill. On a windless morning the water turns to dark glass, holding the paperbarks and the sky so perfectly upside down that it is hard to tell bank from reflection. The catchment behind it is low, flat and sand-bound, and the water crosses it through lake, channel and swamp so slowly that it is easy to forget it is moving at all.

You will hear the reach called the River of Mirrors, and, usually in the same breath, one of only two everglade systems in the world, the other Florida’s. Both belong on a postcard, and both deserve a moment’s scepticism, because there is no scientific definition of an “everglade” at all. Treat it as an evocative label, not a fact. The truth is plainer and no less remarkable: few places on Earth move clear, dark water this slowly through this much sand, whatever we agree to call it.

Keep a second caveat in your pocket, because it corrects the map most people carry. The freshwater everglade is the reach above Cootharaba, not the lake itself. Lake Cootharaba runs barely a metre and a half deep and, fed by tides working up from the estuary below, turns faintly brackish. The true blackwater lies upstream, where the sand country drains in clean and slow, and the further you paddle from the lake the more purely that character shows.

The water is the colour of strong tea, and the colour tells where it comes from. The stain is dissolved tannin, leached from the peaty, acidic litter of the wallum and the paperbark swamps all around, the same blackwater chemistry we meet across the sand country, here gathered off a whole catchment and poured into a river. Because the sand holds almost nothing to buffer it, the water turns sour as well as stained, acidic enough to kill most freshwater life elsewhere in Australia. Not quite all of it, gratifyingly — this is the chemistry the acid frogs live in, and the tiny, threatened honey blue-eye and Oxleyan pygmy perch with them, largely safe here in water too sour for most of their competitors and their imported enemies.

And the banks, if you read them, keep their own accounts. From the canoe you pass out through open lily-water, then the tall blue-grey twig-rush, then the pale-trunked paperbark, then the heath of the drier sand behind. What sets that order above all is how long each plant’s feet stay wet: the shore is a gauge of how many days a year the ground lies underwater.

The everglade does not pack up and dry when the rain stops, because it feeds from below. Beneath the surrounding sand lies an enormous, slow freshwater store, a lens of groundwater held within the Cooloola sand mass, and the everglade is simply that store surfacing, seeping out steadily through the driest months and keeping the dark water moving all year. Recent mapping of the sand mass ties these wetlands and perennial streams tightly to the level and quality of the water table beneath them, a groundwater-dependent ecosystem in the fullest sense.

Which is also where its fragility lies. The everglade leans on a water table you cannot see from the canoe. Draw that table down, or foul it, and it unravels with almost nothing changing at the surface, until, one dry season, the seepage falters and the mirror goes with it.