A crop and cultivar-specific approach to assess future winter chill risk for fruit and nut trees

Anthropogenic climate change will influence winter chill accumulation, with future declines likely in temperate locations. However, these declines only translate as impacts when cultivar winter chilling requirements are not satisfied. This study presents a methodology to evaluate future impacts of declining winter chill through a cultivarspecific approach which is useful for growers, industry and policy-makers to develop adaptation strategies. A risk based system was applied to represent the likelihood of meeting cultivar chilling requirements using low, medium, medium-high and high risk ratings based on percentiles. This was combined with climate projection uncertainty graphically at 16 Australian growing districts historically (1981–2010) and for 2030, 2050 and 2090. The results demonstrated that impacts and likely adaptation options differed between cultivars, some recording limited risk at all sites out to 2090 ('Nonpareil' almond) whilst others recorded greater risk both historically and into the future ('Chandler' walnut). Notably, risk differed across sites and with the future time period. These results highlight which cultivars are susceptible to low winter chill conditions, where this risk does and does not manifest and the different time horizons at which the risk will materialise across Australia's main growing districts. Using this approach, changes in winter chill conditions are presented in a useable form which allows for appropriate climate adaptation strategies to be developed, securing the industries into the future.