The historic impact of climate variability and future climate change projections have been studied to determine how they may affect wheat production on four wheat growing regions of southern Australia.
The effect of rainfall variability was investigated for each of the regions with the resulting study finding that great variability exists in Australian wheat production, much of which is related to variations in ENSO, IOD and SAM. It also highlighted the existing climatic challenges that face wheat producers in each of the locations, regardless of future climate change. The study shows that ENSO and IOD influence growing season rainfall (GSR) in these regions, but to differing extents. In most cases, the IOD has a greater effect on GSR anomaly than El Niño/La Niña alone.
In addition the study investigated the projected change in temperature for each of the four regions with the mean annual temperature likely to increase with time in all four regions. The magnitude of change varies only slightly between locations. The risks of heat shock and frost at flowering were also examined, with variations in risk occurring between regions.
Despite the variability in the model predictions there is a drying trend in all four regions. The biggest decrease in rainfall comes during the critical period from August to October for all regions. This is also the time of year where there is the greatest variation between the models, which indicates that there remains a significant amount of uncertainty about the projections.
It was found that the timing of the first effective rainfall event (the break), over the last 30 years (compared with the long-term) varied considerably between the regions. On average the four regions have seen a delay in the break of seven days. The greatest variations in yearly time of the break occur in the lower rainfall districts. Although there was a trend for the timing of the break to have a bearing on the total GSR it was not statistically significant.
This study has found that a changing climate will influence wheat production in both positive and negative ways across the four regions studied. The study also found that there is already significant variation in wheat production based on existing climate variability, and that this is something that farmers are already dealing with.