Global warming to change how and where fruit grows

Global warming to change how and where fruit grows

Dr Rebecca Darbyshire

Winters in some of Australia’s warmer fruit growing regions may to be too mild to support apple production by 2030, but the outlook is better for the south eastern states.

At the other end of the year, growers in some regions will need to adapt their orchards to cope with extreme heat days, or risk significant loss of fruit from sunburn damage.

These are two of the key findings from a PICCC study undertaken in orchards across Victoria, Tasmania, New South Wales, Western Australia and Queensland over the past few years. The research has provided the first detailed picture of what climate change might mean for Australia’s apple, pear and cherry industries.

Increasing temperatures are likely to be one of the major impacts. Fruit trees need to receive a certain level of ‘chill’ to break the winter dormant phase and allow trees to flower in spring. Projected warmer winters can result in insufficient chill, leading to poorer flowering and reduced fruit production.

The analysis, led by PICCC researchers Rebecca Darbyshire (UM; pictured, above right), Ian Goodwin (AV) and Sigfredo Fuentes (UM), showed that apple trees may not be able to get enough chill through winter to maximise fruit production in WA’s Manjimup and Donnybrook regions, and Queensland’s Applethorpe region. In contrast, Yarra Valley in Victoria, and Huonville and Swansea in Tasmania, were unlikely to be affected out to at least 2050.

Warmer winters are also likely to lead to delayed flowering, which may reduce the risk of frost damage. Several WA sites are already showing noticeable delays, suggesting that the warming climate has already affected trees in that region.

Another element of the project looked at reducing the impact of extreme heat on fruit. Researchers say that the risk of sunburn damage to apples can be reduced by at least 50% with the installation of netting at warm apple growing sites such as Tatura, Victoria and Young, NSW. Cooler sites, including those in Tasmania showed only low risk of heat damage out to 2090.

The study has also enabled researchers to get a better understanding of what climate change will mean for Australia’s favourite apple, the Pink Lady®. Researchers have developed a model that better predicts Pink Lady® flowering timing than the existing method, allowing climate projections to be applied with more confidence.

Rebecca Darbyshire says understanding future climate change impacts is particularly important for the fruit tree industry, because management decisions made now will affect production for the next few decades. 

“Growers are limited in how quickly they can adapt to a changing climate.”

“Changing fruit varieties is a substantial and long term investment for an orchard owner, so we need to be thinking now about likely changes and how best to prepare for them.”

She says the point at which orchard blocks are developed or re-developed is an important opportunity to implement climate adaptation strategies, and that better information and decision support needs to be available to growers to inform the selection of planting material at this time.

This project was supported by funds from the Australian Government Department of Agriculture and Water Resources; the University of Melbourne; Agriculture Victoria; the Department of Agriculture and Fisheries Queensland; Department of Agriculture and Food Western Australia; and the Tasmanian Institute of Agriculture.

For more information on this project visit www.piccc.org.au/research/project/440