Habitat connectivity (get from patch to patch)

Stand at the edge of a surviving patch of bush on this coast and look at what lies between it and the next one along: a road, a fence, a canal, a wide paddock mown to the dirt. To a koala or a bandicoot, that gap is a moat. Clearing slices the forest as much as it shrinks it, cutting what remains into islands, each one stranded from the rest. And an island of habitat, however green its trees, is a trap dressed as a refuge.

A patch behaves very differently once it is cut off. A population marooned on a small remnant has nobody arriving to replace the animals it loses to a car, a dog, a bad fire, a run of disease, and no fresh genes coming in. So it thins. Over the years it quietly empties out, winking to nothing inside a fence meant to keep it safe. Ecologists call the incoming trickle of animals from neighbouring patches the rescue effect. Cut the corridor between two patches and you cut the rescue.

Which is why the most useful thing many landholders here can do is reconnect the patches that are left. The aim is to join the islands up, so a scatter of small, vulnerable populations starts to function as one larger, better-buffered one. It happens three ways. You replant corridors along the creek and drainage lines that already thread between remnants, the obvious routes to rebuild first. You hold on to the lone paddock giants and roadside trees that let an animal cross open ground in short hops, stepping-stones through country that would otherwise be a gulf. The third is the slow one. You keep the big, old, hollow-bearing veterans, because a corridor of young saplings is a street with no houses on it: a way through, but nowhere to live. The oldest of those trees carry hollows that took a century and more to form and cannot be replaced in any human timeframe, so a corridor is only finished when it has somewhere to stop as well as somewhere to travel.

The animals that need this most are the specialists strung thinly across the landscape, staked on a resource that turns up here and there and nowhere in between. The koala must reach its particular feed trees, through enough forest, joined closely enough to move without coming to ground, where the traffic and the dogs are. The glossy black-cockatoo commutes for a living, between the she-oak stands it feeds in and the big old hollows it nests in, rarely the same place twice. Neither asks for any single block to be flawless. Each asks the landscape the same plain question — can I get from here to there? The same short roll-call keeps turning up on the lists of animals in decline, undone less by the loss of one perfect patch than by the loss of the joins between them.

There is a quiet economy to this, too. Connectivity is often the cheapest care going, because so much of it is retention rather than replanting: not felling the paddock giant, not clearing the creek line, not tidying away the half-dead tree. It is restoration that lets the animals do their own moving, once the way reopens. In the most chopped-up country, the flying-foxes ranging tens of kilometres a night, carrying seed and pollen between fragments, are sometimes the only thing still crossing the gaps.

On a coast that keeps subdividing, one of the fastest-growing regions in the country, the islands are still being made faster than they are joined. Holding the connections we have, and rebuilding the ones already gone, is the work that lets a landscape of imperfect patches go on rescuing itself.