Samphire (glasswort)

Walk the tidal flats north of Adelaide in high summer and you could be forgiven for thinking the ground itself has caught fire. Not flame — colour: whole hectares of low, leafless, knuckly little shrubs blushing from blue-green to a deep, arterial crimson, as if the mud had decided to bleed. This is samphire, and the colour is not a bloom or a decoration but a plant running out of room to put its salt.

Samphire is a family of species that botanists file under the genus Tecticornia — glassworts, jointed and fleshy, each stem built from stacked, sausage-like segments with no leaves to speak of, because leaves are exactly the kind of surface a salt-drenched plant cannot afford. What samphire does instead is the trick that should, by the ordinary rules of plant physiology, kill it outright: it drinks the brine (Tecticornia 2024). An ordinary plant set down in water this salty would find water drawn out of its own cells rather than in, and shrivel from the inside within days. Samphire swells with the salt, packing it away into its own succulent flesh, diluting a poison it cannot avoid rather than trying to keep it out. As the plant keeps drinking through a long dry summer, concentrating salt it has nowhere else to send, it eventually shows the strain in colour — the whole flat flushing red for a few weeks before the winter rains dilute the load and the green returns.

That trick has made samphire the plant that names an entire stretch of coast, and the structural floor of a habitat far more valuable than its grey, mosquito-humming appearance suggests: waterlogged Tecticornia mud locks away carbon faster, hectare for hectare, than most forests manage (Macreadie 2017), and its thickets shelter a small, dun-coloured bird — the slender-billed thornbill — found almost nowhere else on Earth.

But the trick has a weakness the plant cannot solve by drinking harder. On the eastern side of Gulf St Vincent, populations of the shrubby samphire Tecticornia arbuscula have declined sharply, with sea level rising faster, in places, than the plant can colonise new ground behind it (Delta 2017). Australia’s temperate coastal saltmarsh — the community samphire builds — is now formally listed as a nationally vulnerable ecological community (Saltmarsh 2013). A plant that beat the sea’s chemistry is now racing its geometry, and for the moment, the sea is winning.