Trends in wheat yields under representative climate futures: Implications for climate adaptation

Underestimating the impacts of climate change on agricultural production could lead to complacency about the potential adaptation challenges. This study used a Representative Climate Futures (RCF) approach to model projected wheat yields under climate change in Australia. It simulated the range of impacts, resulting from a subset of individual Global Climate Models (GCMs), on wheat production in the major wheat regions of Australia. The study used RCFs that represented 'most-likely', 'best' and 'worst' cases across multiple Representative Concentration pathways (RCPs). Median wheat yields modelled for the South West Australia projected declines between 26% and 38%, under a 'most-likely' case for RCP 4.5 by 2090, and between 41% and 49%, under a 'most-likely' case for RCP 8.5. Median wheat yields declined under RCP 8.5 for the 'most-likely' case across the majority of wheat producing regions, with a range of 1% to 49%. Greater declines were projected under the 'worst' cases of hottest and driest climates. However, the 'best' cases of least warm and wetter climates projected an increase in median wheat yield, a range of 2% to 87%. Variability also changed from the baseline under all projected RCFs and across all regions, with a standard deviation of up to 2.46 t/ha under the 'most likely' case at a site in south-eastern Australia. These likely shifts in the size and reliability of yields, combined with concurrent climate change impacts on other factors, mean that agriculture faces significant adaptation challenges, particularly under some of the 'most-likely' scenarios and all of the 'worst' case scenarios. Further work is required to explore how scenarios in one region relate to those in other regions and thus the overall outcome at the continental scale.