Biological invasion (they don't add — they overwrite)

In 1935 someone in Queensland unlatched a crate of South American toads onto the cane fields, confident they would deal with the beetles chewing the crop that then ruled this coast. The toads did almost nothing to the beetles. They bred in prodigious numbers instead, poisoned the native goannas and quolls that tried to eat them, and set off across the continent in a slow toxic tide still advancing. An introduced species almost never simply adds itself to the list of what lives here. It crosses names off.

The reason sits in an idea these guides keep returning to: every native plant and animal is a bundle of needs and defences shaped by the particular neighbours it evolved alongside. Against a player it never met, it has nothing ready.

The small and medium mammals had no behaviour tuned to a fox that hunts by night or a cat that kills beyond hunger, and between them those two imports became the most damaging introduced predators those animals have met. The little diggers and hoppers were simply removed. The native predators had no tolerance for the toad’s poison, so the ones that ate it died and the toad went on unchecked. The mosquitofish, slipped into the creeks, met tadpoles with no defence and stripped them out, except in the sour blackwater of the wallum, where the acidity keeps the fish at bay. In each case the import does the native’s job badly, or not at all, while sitting squarely in its place, taking the light and the ground the native needed.

The plants overwrite most visibly. Lantana, a garden ornamental gone feral, throws dense, thorny thickets across cleared ground and shades out everything beneath it. Camphor laurel, planted as a handsome street tree, seeds itself into abandoned pasture and gully and grows into whole weed-forests where rainforest should be. Both are so common now that a newcomer might take them for native bush, which is the danger: the green is not always the country’s own. Read right, a wall of lantana or a stand of camphor laurel is not random bad luck but disturbance made visible, a sign that the ground was cleared or drained or broken first and colonised by an import second. The weed is the scar. The wound came first.

Which is why the damage is so stubborn. Because the invader overwrote a working system rather than taking an empty chair, you can rarely undo it by pulling the weed alone. The cleared ground just grows another. Mending, where it works, is patient and indirect. You restore the conditions the native cover needed, the intact edge and the unenriched soil and the missing predator, rather than putting the lost thing back by hand. The settlers did more than take from this coast. They added, and the addition worked as subtraction: a hardier, borrowed cast laid over a native one that had no way to say no.