Climate change is moving a line drawn across South Australian maps 150 years ago to indicate the northern boundary of the state's good agricultural land, scientists have said.

Farmers have used that imaginary boundary to determine where productive land ends and marginal land starts, but agricultural scientists say climate change is shifting the line south.

Goyder's Line was first drawn by the state's surveyor-general in 1865, but the amount of arable land in SA is now decreasing.

Farmers, such as Kym Fromm, who live near the edge of Goyder's Line have been watching and measuring as their regional climate changes.

"A special interest for me, since I live a mile south of Goyder's Line, is that if the climate does change we're very sensitive to that change because we could quite easily end up in almost pastoral country ... if it creeps down south," he said.

Goyder's Line, marked in blue, stretches across South Australia. ( Supplied: District Council of Orroroo-Carrieton )

That would mean a big farming change for Mr Fromm, at Orroroo, where he had been growing wheat for 40 years.

He said most farmers were already adapting their cropping practices due to their expectation of hotter, drier conditions in future years.

"Ninety per cent of them would say, 'No, climate change isn't real, especially human-induced climate change'," he said..

"But they're still adjusting their farming practices based on what they see so from my point of view I don't really care why they're doing it.

"The fact is that they're doing it. They're adjusting their farming practice to what they see."

Mr Fromm said farmers were keen to stay ahead of the shifting line.

"If it does happen that we are in a changing climate that's actually not going to change back to normal, that's going to have huge implications on the financial status of farmers around here," he said.

"That's probably my main concern. So far, when I've seen the changes that farmers have made and the way that they've been able to adapt so quickly already. I'm actually a lot more hopeful now."

Climate scientist warns on rainfall reliability

Goyder's Line stretches across maps of South Australia from Ceduna in the west, across to Spencer Gulf, north to Orroroo, then south and east across to the Victorian border at Pinnaroo.

Climate scientist with Primary Industries SA Peter Hayman said farmers living close to the line had good reason to be worried.

"If we were to say that would a warming, drying trend in the future put a downward shift on Goyder's Line, I think that's definitely the case," he said.

"Climate science is less clear about trends for rainfall. There's really worrying aspects about the future for rainfall, but in coming decades there's a bit of uncertainty about how that will exactly play out."

Despite rainfall questions, he expressed greater certainty about temperatures.

"What there's more confidence in is the change in temperature, which would mean that wheat would grow faster," he said.

Malcolm Parish says Clare Valley viticulturists are concerned about the effects of climate change on their wine. ( ABC: Michael Dulaney )

"That can be dealt with to an extent, but if the change in temperature is delivered in more heat events — so these spring heat events like we've had this last year — if get more of those then that's a major concern."

Further south and closer to Adelaide, the Clare Valley is known for its premium wines.

Grape growers such as Malcolm Parish are searching abroad for new varieties they can plant which will better cope with hotter weather.

"We're looking to different European countries now for what we're planting because we're looking for something that can handle the warmer temperature," he said.

"Rather than perhaps the old French Bordeaux varieties that we've hung our hat on, we're thinking we're going to have to have a percentage of these newer varieties that will actually handle this different weather."

While he said it was unlikely Goyder's Line would creep as far south as Clare, a changing climate could still threaten the varieties of grapes grown in the region and their delicate flavour profile.

"Our Riesling here would be very susceptible to climate change because that is a soft-skin white, and Clare has made its name on Riesling," he said.

"If you get a warmer year the grapes will create their sugar earlier, they'll develop a sweetness but they don't necessarily develop the fruit character you're looking for."

Goyder's work remains important 150 years later

The locals of Orroroo unveiled a corrugated iron statue of George Goyder in their town recently, indicating how seriously they take his calculations made during drought conditions in 1864-65.

The imaginary line was first drawn by the surveyor-general to indicate that graziers north of that line would need government support to be able to farm and later became considered the rainfall line across SA.

Goyder made extensive expeditions across rural areas of the state and mapped 19th century changes in the vegetation.

George Goyder mapped changing vegetation in rural SA 150 years ago. ( Supplied: Bush Telegraph )

Adelaide now has a Goyder Institute, where water research is done.

One of its researchers, Professor Simon Beecham, said of Goyder: "When you think what he did back in those times, it is quite phenomenal.

"Rainfall records hadn't really started at that time so he had nothing to go on other than his own intuition and observational powers, and I think his observational powers were quite amazing.

"It's proven to be very, very accurate even though it was done purely on observation rather than any numerical analysis."

The iron artwork of Goyder, now proudly on show at Orroroo, was the work of Renmark sculptor Dudley Siviour and was unveiled by Goyder's great-great grandson and great-great-great granddaughter.

Orroroo Carrieton District Council chair Kathie Bowman sand the line of maps had played a crucial role in the state's agricultural development over the years.

"It seems pretty obvious to us who live here. It does define a lot about the Orroroo district, about the more reliable cropping country south of the line and the more marginal cropping and grazing country north of the line," she said.

Professor Beecham said the Goyder Institute researchers agreed the regional climate was changing.

"The area to the north of where the rainfall would have fallen is now drier," he agreed.

"Our work has demonstrated really that that line is almost certainly going to be drifting southwards. [Goyder's] observations of vegetation and where agriculture is sustainable I think would not be the same [now].

"I think he'd be saying 'Yes, it's further south'."