The wallum

The wallum is the low, hard-leaved heath of the sand coast. Its poverty is the part that gets talked about, and it is argued out in its own right elsewhere. This piece stands back and takes the heath whole, because the wallum is not run by poverty alone. It runs on four scarcities at once, and only where all four line up does true wallum appear.

First, the name. “Wallum” is widely reported to come from the Kabi Kabi word for the corky-barked banksia that crowns the heath, Banksia aemula. It makes a fair emblem, a shrub that lives on next to nothing, and its own portrait can be read for how a single plant pulls that off.

The first scarcity is nutrient. Behind the beaches lie old dunes of bleached quartz sand, rinsed by rain for so long that the phosphorus every living thing needs has drained below the roots and gone. On ground this hungry no plant grows fast enough to crowd the rest out, so instead of a few winners the heath fills with hundreds of specialists, each prising a living from the sand a different way: some feeding fungi, some mining phosphorus by chemistry, some renting nitrogen-fixing bacteria, and some, like the sundews and the bladderworts, catching and consuming small animals to make up the shortfall. The bladderwort’s cocked traps snap shut on a passing water-flea in under a thousandth of a second, one of the fastest movements a plant makes anywhere. The leaves overhead are hard, small and built to last, the mean, thrifty foliage of plants with no phosphorus to waste on cheap, throwaway leaves.

The second scarcity is sweetness, or the lack of it. Follow a track into a damp swale and the sand glistens with dark, sour water, stained by the slow leaching of the peaty ground. To most freshwater life this blackwater is lethal. To the wallum froglet and its relatives it is a refuge, because water this sour shuts out their commoner cousins and, in most of their breeding pools, any fish at all — including the invading mosquitofish that cleans out tadpoles wherever it reaches them. How that shelter works, and how easily it fails, is taken up in its own piece. Here it is enough that the most hostile water on the coast is the making of its own frogs.

The third scarcity is fire. The timing of it is the hard part. The wallum is the most fire-shaped country on the gradient, and it needs flame in the particular rhythm its plants grew up with. Many of them hoard years of seed against a burn and release it only onto the cleared, ash-fed ground a fire opens. Withhold fire and the heath grows choked and rank; burn it too often and the seed-bankers never refill their store. The ground parrot, a grass-green bird that has given up trees to spend its whole life down in the heath, is the strictest test of all this. It needs large, unbroken tracts of just the right age since fire, and slips away without a sound when the burning goes wrong.

The fourth scarcity is water, and it is the one you cannot see. Under the driest-looking dune sits a great freshwater store held in the sand itself, and that hidden reserve keeps the swamps wet and the blackwater sour straight through the dry season. Drain it, or let ordinary water seep in and sweeten the sand, and the arrangement fails quietly, with no warning at ground level until the harm is beyond undoing.

Pull any one of the four threads and the rest unravel. That is why the wallum cannot be dug up and reassembled somewhere more convenient. Twice it nearly was, written off as worthless scrub by people who could price the mineral in the sand and not the thing growing on it. It is the most elaborate structure this coast builds out of nothing at all, and it holds together only as long as its four poverties are all left in place.