Climate change: What it means for fruits

New research has revealed how climate change will impact Australia’s $AU3.2 billion fruit farming industry, and it is likely to prompt a major shift in how and what can be grown.

The new report, led by University of Melbourne researchers, shows that by 2030, winters in some of Australia’s warmer fruit-growing regions may be too mild to support apple production.

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

These are two of the key findings from a national project led by the Primary Industries Climate Challenges Centre (PICCC), a joint venture between the University of Melbourne and Agriculture Victoria that collaborates on climate research for Australian agriculture.

Dr Rebecca Darbyshire and Dr Sigfredo Fuentes, from the Faculty of Veterinary and Agricultural Sciences, worked alongside Agriculture Victoria’s Dr Ian Goodwin, researchers from Tasmania, Western Australia and Queensland, and fruit growers and consultants from around Australia to provide the first detailed picture of what climate change might mean for Australia’s apple, pear and cherry industries.

the chill factor

Increasing temperatures are likely to have a significant impact on Australia’s fruit production, according to the published research.

“We found there’s a significant risk of insufficient accumulation of winter chill in some current production areas, including WA’s Manjimup and Donnybrook regions and the Applethorpe region in Queensland,” Dr Darbyshire said.

“While the likely future risk of climate change is varied dependent on the timeline and location, the research suggests larger transformational change might need to be considered.

“That means potentially changing the crop growers’ produce.”

Dr Darbyshire and her team used a range of different models to predict future climate risks, including deploying physiological models run with temperature predictions provided by CSIRO.

When it comes to increasing temperatures, the risk to fruit comes from a lack of ‘chill requirement’, she said.

What is not commonly known is that fruit trees enter a dormant phase over winter. It’s an evolutionary strategy that prevents ‘cold damage’ to shoots and flowers by stopping them from appearing during a winter warm spell.

Dormancy ends not in response to warmer temperatures as you might think, but rather when the trees have received a certain amount of cold winter weather, termed ‘chill’.

At this point, having met their ‘chill requirement’, trees sense that winter has finished and will flower in response to warm temperatures.

What complicates this for fruit growers is that different types of fruit, and even different varieties of the same fruit, require different amounts of chill to end their dormant phases.

And if trees don’t receive enough chill, spring flowering will be light and fruit yields low, impacting a grower’s bottom line as well as availability on supermarket shelves.

By comparing the known ‘chill requirements’ for a range of different fruits with the climate projections for each region, the research team showed that by 2030, Golden Delicious apples and Lapins cherries may be unable to get enough winter chill to maximise fruit production in some areas of WA and Queensland, with growers there advised to transition to different varieties or crops that require less chill by 2030.

In contrast, the Yarra Valley in Victoria, and Huonville and Swansea in Tasmania, were unlikely to be affected until at least 2090.

The heat factor

Another aspect of the project looked at reducing the impact of extreme heat on fruit. For this, researchers focused on the Royal Gala apple, a variety that matures during January and February, making it highly vulnerable to sun damage.

They found the risk of damage can be reduced by at least 50 per cent with the installation of netting at hot summer sites such as Shepparton in Victoria and Young in NSW.

Cooler summer sites, like Huonville and Spreyton in Tasmania, were found to have low risk of sunburn damage even by 2090, and little benefit of installing netting.

New knowledge

The research also provides a knowledge boost for growers of Australia’s favourite apple, Pink Lady®, with the team developing a model that predicts Pink Lady® flowering timing.

This gives more confidence in predicting the impact of a changing climate on vital processes such as cross-pollination, and the likelihood of damaging spring frost events, so growers and the industry can plan ahead more effectively.

Dr Darbyshire said understanding future climate change impacts across growing regions and different varieties is particularly important for the fruit tree industry, because management decisions made now will affect production for the next few decades.

“Unlike annual crop growers – say, a grain farmer or vegetable grower – fruit growers are limited in how quickly they can adapt to a changing climate,” she said.

“Changing from a Royal Gala crop to Pink Lady® or even an apricot crop, for example, is a substantial and long-term investment for an orchard owner, so we need to be thinking about likely changes now and how best to prepare for them.”

She said the point at which orchard blocks are developed and re-developed is when growers need to be considering implementing climate adaptation strategies.

That is when better information and decision support needs to be available.

Although growers can reasonably easily decide to make short-term, incremental adaptations (like installing netting), researchers, industry and government have an important role to play in adaptation, particularly for more transformative changes.

Researchers need to demonstrate the benefits of adaptation options, industry needs to promote change amongst growers, and governments must ensure policy settings encourage change, Dr Darbyshire explained.

It’s not a one-size-fits-all approach though. The vastness of Australia’s growing regions, and diversity of fruit species and cultivars planted means successful adaptation will differ depending on timing, location, and crop type.

This project was supported by funds from the 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 and for local contacts visit www.piccc.org.au/research/project/440.

Banner: Shutterstock