CLIMATE change has reduced potential yields across Australia’s wheat growing regions by 47 kilograms a year in the last quarter century, according to the latest CSIRO research.
Depending on your outlook, farmers have done well to maintain productivity while climate change bites. Or we’ve witnessed global warming burn up 25 years of hard graft for no gain.
But either way you slice it, any future gains for wheat growers will be hard won.
“We are looking at 26 years of stagnation in wheat yield,” said CSIRO Agriculture and Food senior research scientist Dr Zvi Hochman.
The findings are presented in a study which draws on data from a representative sample across wheat growing regions between 1990 to 2015.
Its findings showed maximum daily temperatures increased one degree on average across the regions, coupled with a roughly 30 per cent decline in average rainfall (71.8 millimetres) which was compounded by increased climate variability.
While wheat growers’ productivity rose about 25kg a hectare each year over the last 25 years, climate change had cruelled potential gains.
“Adopting new technology, and the good work done in research and extension, has just enabled farmers to keep up and stay in the same spot,” said Dr Hochman, who presented the findings of a study he co-authored at the recent Australian Bureau of Agricultural and Resource Economics and Sciences Outlook 2017 conference.
The study compared actual yields to potential maximum wheat yields, which were calculated by assuming best practice in land management, seed variety selection, fertiliser use and so on.
It found the yield potential realised by growers had risen from 38pc on average to 55pc, which showed “farmers are compensating for worse conditions by using more of yield potential available to them”.
Reduced potential yield is largely explained by water stress and by higher temperatures hastening the period in which yield can be formed, Dr Hochman said.
Alarmingly, he warned actual yields will retreat over the next 25 years if current climate trends continue, even with projected technological gains.
The findings isolated impacts of individual factors and found rising temperature alone caused an 8kg/ha a year drop to the overall 47kg figure. Dr Hochman said while rising carbon dioxide was cited by some as a good plant food, the study found increased CO2 levels had boosted potential yields by about 7kg, which was “more than cancelled out” by the impact of increased temperatures.
Growers deliver about 20kg/ha per millimetre of rain based on average water use efficiency. That means without the industry’s productivity gains increasing water use efficiency, declining rainfall of 72mm a year would have reduced an annual yield by around 1.4t/ha .
CSIRO’s study found there was a one in 100 billion chance these impacts were caused by random climate variability.