If this is climate change at work, he ponders, it won’t leave him all that much of a future. The past two disastrous seasons confounded all his experience of cropping in South Australia’s drought-prone Mid North. “Everything happened back-to-front,” he sighs, nursing a coffee in his leathery hands. “The rain came in summer when we didn’t need it, it was dry all winter, and what was left of the crop got burned off when the northerlies started up in spring. Crazy stuff, mate, even for this country.”

The implications go far beyond his 2000ha property near Pekina, on George Goyder’s famous “line of reliable rainfall”, three hours’ drive from Adelaide. For more than 140 years this line has marked the limit of possibility for

broadacre farming in the nation’s driest state. The colonial surveyor-general was undoubtedly a man ahead of his time. In the 1860s, he mapped where crops could be grown and where they could not. The debate he unleashed has never been more passionately argued than it is today, as drought and global warming raise new concerns about how intensively marginal agricultural lands should be worked, if at all.

The questions echo across the land, through the towns and cities, all the way to the marbled halls of federal Parliament. Are some growers simply in the wrong place, on country that can no longer sustain them? Could advances in farm practices and new crop varieties be their salvation? Or is the fight already lost (in which case, why should taxpayers throw good money after bad by subsidising them)?

Goyder’s answer, all those years ago, was to partition South Australia along what turned out to be the 10 inch (254mm) isohyet. (An isohyet is a line drawn on a map connecting points that receive equal rainfall.) It was an astonishing feat. With limited climate data he followed the rainfall contour on horseback, tracking the tell-tale break in the landscape where eucalypt forest and native grasslands gave way to sparse saltbush country. For every mile ventured beyond the line, rainfall was said to drop by an inch, until it became so low there was no point doing the arithmetic.

People set out to try to prove Goyder wrong by farming beyond the line. Few succeeded. Being on the safe side of the line – as 51-year-old Fromm is, if barely – instilled confidence that drought and disastrous seasons could be endured.

No longer. The reality of climate change has swept away the certainties of Goyder, feeding into wider concern that rising temperatures and changing rainfall patterns will push vast tracts of marginal agricultural land past the point of viability. In the worst-case scenarios developed by South Australia’s Research and Development Institute and CSIRO, the line will shift south, rolling over Fromm’s dusty fields, perhaps all the way to the vineyards of the Clare Valley, about 120km distant.

Nearly everyone seems to have a theory about where the line will end up, and what that means for hardscrabble farming. Fromm is holding on – just. In 2006, he lost his entire crop. Last year was even more devastating, because for a while he had dared to believe the worst was over. Good rains in January 2007 were followed by a soaking in May, persuading him to go for broke and plant an extra paddock. Then, nothing. For a second successive year the winter rains failed.

Meticulously, he diarised the whole sorry saga. Fromm stabs a meaty finger at the entry for August 31, 2007: “Windy, 33 degrees,” he declaims, “hottest winter’s day I’ve had.” A scorching northerly began blowing on October 5 – the barley had “gone off” and the wheat was severely stressed. By the end of the month temperatures had hit 40 degrees. “Really bad,” he noted on the 27th, “Severely windy … dust everywhere.” Eventually he brought in a crop, but it was too meagre to retrieve the season. Despite near-record wheat prices he wound up $50,000 further in debt. “We had a 10 per cent chance of it going bad and, guess what, it did,” he says, draining his coffee, a long, sweaty afternoon’s work on the tractor beckoning. What he desperately needs is a return to something like normal conditions this year. If he loses another crop, he doesn’t know what will happen. Truth be told, no one really does. ...