Dune pioneers

The bare sand behind the beach shifts underfoot. Salt spray scours it, furnace heat bakes it, and at first it holds no soil at all. It is harder ground to live on than the wallum behind it. Almost nothing grows there. Almost nothing, that is, but a small, tough crew of pioneers that hold the sand still long enough for anything else to follow.

The chief of them is spinifex, not the spiky desert spinifex of the inland but a sprawling coastal grass of the same borrowed name. It throws long runners across the open sand, pinning it down and trapping wind-blown grains until a dune builds around it. Beside it grows pigface, its fat leaves swollen with stored water against the drought and salt, flinging improbable magenta flowers across the bare ground. And goat’s-foot, a beach morning-glory, runs purple-flowered vines metres across the surface like rope flung across a deck. Three plants, three shapes, and the same effect. They catch the moving sand and make it settle.

A grain of sand blowing along the beach travels until something stops it, and a spinifex runner or a mat of pigface is exactly that something. Sand piles into the shelter of the plant. The plant grows up through the fresh sand. More sand piles in, and grain by grain a vegetated ridge rises out of the flat, built literally by the plants standing on it. Each survives the front on the same thrifty, hard-wearing economy the rest of the poor country runs on, all leathery or water-storing tissue and a low profile to the sun and salt, made to endure rather than to grow fast and soft. But the sand-binding is theirs alone.

And in doing it, these unregarded plants perform a service the whole coast leans on. The vegetated foredune is the first and cheapest sea defence anyone has, a wall of held sand between the ocean and everything behind it, thrown up and maintained for free by a handful of species most beachgoers step straight over. Strip them off with too many feet or too many vehicles and the sand comes loose: the dune blows out and walks inland with the next big wind, a sandblow that buries the scrub in its path.

Behind the shifting front, where the pioneers have done their work and the sand has finally come to rest, the vegetation thickens into low dune scrub, and then, on the older and steadier sand further back, into the hard-leaved heath of the wallum. Read the sequence outward from the sea and it is a hand-off. The pioneers make the ground stand still, and the scrub and the heath move in behind the shelter they build.

Notice what the pioneers give, and what they do not. They do not make the sand rich. The ground behind them stays as hungry as ever, and the wallum’s extravagant flowering is founded on that poverty. They give stability. It is the least celebrated engineering on the coast, done for nothing by plants nobody looks at twice, and everything landward of the beach stands on the back of it.