Australia's wheat productivity has flatlined as a direct result of climate change, according to CSIRO research.

While 2016 set a new national wheat harvest record, the national science organisation's findings indicate that result masks a more troubling long-term trend.

While Australian wheat yields tripled between 1900 and 1990, growth stagnated over the following 25 years.

A CSIRO study which monitored 50 sites across Australia's wheat zone between 1990 and 2015 found that climate change was the clear cause of the decline.

That trend remained, even after the bumper 2016 figures were included.

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Across those sites, average maximum temperatures increased by more than 1 degree over 26 years during the months when crops were growing — a significant increase. Rainfall during the growing period declined by about 72 millimetres, or 28 per cent.

Zvi Hochman, a senior research scientist with CSIRO Agriculture and Food said the team considered whether other factors could have shared the blame, such as investment in research and development (R&D), changing patterns of land use, and soil fertility. Listen Duration: 9 minutes 43 seconds 9 m Listen Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Zvi Hochman, CSIRO senior research scientist ( Anna Vidot ) Download 8.9 MB

But those could all be ruled out: investment in grains R&D was stable, changing land-use patterns should have favoured wheat production, and soil management improved as farmers adopted new techniques such as zero-till.

"Climate variability can make it look as if there is no trend, just one year's good and one year's bad, but we've statistically analysed the trend that we observed," Dr Hochman said.

"The chance of that just being variable climate without the underlying factor [of climate change] is less than one in 100 billion."

Farmers and researchers 'working hard to stand still' as climate changes: CSIRO

The CSIRO study found that wheat growers made significant productivity gains over the 26 years of the study.

But instead of that translating to significantly improved yields, the research team found that those gains were only cancelling out the negative climatic changes.

"Farmers, backed by research and by technology, have been working really hard to keep up, to adapt, to the tougher conditions, and have succeeded," Dr Hochman said.

"But they have succeeded in standing still, not in moving forward."

While farmers' productivity is expected to continue to improve over the next 25 years, CSIRO scientists say there is a ceiling on those gains.

If climatic changes continue on the trajectory the CSIRO observed at its research sites, Dr Hochman warns productivity gains will no longer be able to compensate for the decline.

"If we assume the same trend continues, then there's a point at which the two lines cross each other - in about 20 years' time - and by then we will start to see declining yields.

"The sad thing is that, at the same time, world demand for food is increasing and the opportunity for Australia to contribute to global food security, and for farmers to benefit from these growing markets, looks to be in doubt."

Adaptation decisions for farmers

While the CSIRO study did not record a positive trend at any of its 50 research sites, the declining trend was not uniform.

"Some farmers should be more alarmed than others," Dr Hochman said.

He expects that some farmers will move out of grain growing and choose livestock or other options, as climatic conditions decline.

"Other farmers in the more favourable parts of the wheat growing areas will be able to continue to do quite well, but overall the trend seems to be a negative one.

As for the 2016 anomaly, Dr Hochman said it was not the only outlier that was either better or worse than the trend, but that the trend line remained statistically sound even after the record year was factored in.

"There's a difference between weather and climate.

"Don't expect to see many more years like last year in the next 26 years."