Goyder's Line (where the saltbush begins)

In 1865, after a punishing drought, South Australia’s Surveyor-General George Woodroffe Goyder rode north through the colony with a brief that sounds almost poetic for a government survey: to find, and draw on a map, the line beyond which the rain could no longer be trusted to grow a crop. He did not wait for decades of rain-gauge records that did not yet exist. He read the country. Where the better grasses and scrub gave way to saltbush and bluebush, he marked his line — because the plants had already integrated a century of droughts and wet years into a single honest verdict about the water (Goyder 1865).

The line he drew runs, in modern terms, close to the 300-millimetre reliable-rainfall isohyet, and it separates two Australias. South and west of it lies country wet enough, most years, to farm; north and east of it lies the saltbush and mallee, where wheat is a gamble you will eventually lose. That vegetation boundary is the summer-drought climate made visible: the same Mediterranean rhythm of wet winters and killing-dry summers that sorts every plant community in this book, drawing a hard edge on the map where the water finally fails (Cowling 1996).

Goyder’s Line is a lesson in reading absence. In the wet years of the 1870s settlers pushed wheat north of it on the hopeful slogan that “rain follows the plough,” and when the droughts returned they were ruined, leaving behind stone farmhouses you can still find stranded above the line. The plants had told the truth; the people had preferred the hope. Learning to see the line — in the saltbush, in the abandoned walls — is a first exercise in the skill the whole app is about: reading a landscape for what its water will and will not allow.