A vintage crop ahead
[ The University of Melbourne Voice Vol. 5, No. 3
8 June - 12 July 2009 ]
The Australian wine industry is developing the resources and adaptive technologies to meet the challenges of climate change, Nerissa Hannink discovers.
In January and February 2009 south–eastern Australia was subjected to record high temperatures that, in many regions, also persisted for record durations. Unfortunately for the wine industry, these areas are home to Australia’s key wine-growing (viticulture) regions.
Professor Snow Barlow, who heads the University of Melbourne Viticulture Group (VitUM) based in the School of Land and Environment, says that soon after the heatwaves reports emerged of unprecedented impacts on vineyards with significant heat-stress related crop losses recorded at some sites.
“Across the winegrowing regions the heatwave varied in intensity and duration. For example records from Mildura indicate that there were 12 consecutive days above 40°C, in Tasmania one spike in temperature was observed and the Mornington Peninsula experienced two heat-spikes,” Professor Barlow says.
With climate change projections indicating extreme weather events will become more frequent and occur with greater intensity, researchers are using the wine industry as a model to examine potential adaptation strategies for food production more generally, with encouraging results.
Associate Professor Greg Dunn from the School of Land of Environment’s Dookie campus has a particular interest in how our changing environment will impact the physiology of the vines.
“We know that climate change will bring reduced rainfall and increased temperatures, and for the wine industry this will most likely translate into earlier budburst dates and earlier harvest dates. Harvest compression has also already been observed in some regions in recent years,” says Associate Professor Dunn.
“Documenting both the impact and the management strategies employed to cope in high temperatures is one area the industry will need to understand better. The VitUM team has conducted a survey of vineyards affected in the 2009 heatwave in order to address this.”
Dr Leanne Webb, a former viticulturist and now researcher in the VitUM group and the Centre for Australian Weather and Climate Research, led the heatwave study.
“In effect the heatwave created a huge natural experiment where grapes, managed in different ways, were exposed to different levels of extreme heat.
“We wanted to examine the heatwave impact and management strategies employed as they varied between regions, within regions and within vineyards. Sonja Needs organised the logistics of the visits to ten randomly selected vineyards in ten regions. All of the information was gathered by our team of six within six weeks of the heatwave. We noted that while the effects on grapevines ranged from stalled growth, leaf burn and shedding to berry shrivel and sunburn, it was observed that not all vineyards were similarly affected.”
The information was then analysed to establish any links between the impacts in vineyards with temperature records from the National Climate Centre.
“We found that the variation of impact was not generally related to the level of temperature to which the vines were exposed, but to the regional or inter-regional management strategies and viticultural practices employed.
“Variation in the management strategies, either traditional approaches or reactive management, has highlighted potential adaptive management strategies for dealing with extreme heat events in future.”
Over all of the regions, four management options appeared to have a major influence on minimising damage. Generally there was more reported damage where water was not available, grapevine rows were oriented in a north-south direction, berry development was in the ripening phase and bunches were exposed to the sun’s radiation.
Relatively higher levels of damage were reported in the properties surveyed in the Mornington Peninsula, McLaren Vale, Barossa Valley and Rutherglen areas. The more severe impact may have arisen from the area’s management practices which are typically geared to exposing fruit in order to minimise disease pressure (the opposite strategy of managing for extreme heat).
In some cases if the crops were ‘dry-grown’ (unirrigated) or water was not accessible (due to the continuing long-term drought in south-eastern Australia) high levels of damage were reported.
Low levels of damage were reported in the Murray Darling/Swan Hill and Riverland regions mainly because current vineyard practices (including canopy growth and water management) address the region’s regular exposure to high temperatures.
“In the future viticultural management will be, even more than previously, a risk minimisation exercise. The issues of fruit exposure, the cost of water security, rootstock, vine training, and choice of row orientation may need to be re-evaluated being mindful of more typical climate variability, but with due consideration of a hotter projected climate,” says Dr Webb.
“Capturing the observations and management decisions made by a cross-section of winegrape industry practitioners so soon after the severe heatwave has revealed management strategies that, moving forward, may assist this important sector and other horticultural enterprises to cope in an increasingly challenging environment.”
Professor Barlow notes that in many ways the viticulture industry is well-suited to be a forerunner in climate change adaptation.
“The wine industry is spread over many different regions, all over the world. It encompasses many different horticultural techniques and plant varieties, thereby creating some scope for change.
“We are at the stage where we need to move past the debate over whether climate change is happening and move on to how best can we adapt to the inevitable climate change. Our vulnerability to climate change will depend on our willingness and capacity to adapt quickly when confronted with shifts in climate. Australian agriculture will be challenged by climate change and particularly decreasing rainfall in southern Australia.
“It is imperative that we begin immediately to develop these adaptive management strategies because as Darwin reminded us: It is those who adapt first that survive.”
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