Fears spark smoke research

For a wine-producing region that conducts its business between latitudes 41° and 43° South, Tasmania has always had to contend with a range of adverse growing conditions created under the influence of the Southern Ocean.

But with the first significant effects of climate change also beginning to contribute to grower pressures, Tasmania's 230 or so individual vineyards are now developing greater awareness of a range of new and unfamiliar viticultural risks - including those created by uncontrolled bushfire activity.

In early 2019, a small number south of Hobart would find themselves become players in cutting edge smoke taint investigations in the State. These would harness the knowledge, skills and experience of leading Tasmanian winemakers and the collaborative engagement of a number of key agencies involved in industry research and analysis: La Trobe University's Department of Animal, Plant and Soil Sciences; Agriculture Victoria; and the Environment Protection Authority (EPA) Tasmania. Engaged in correlating results were commercial laboratories at the Australian Wine Research Institute and Vintessentials.

Their collective plan - to help create an early warning system of smoke detection, in order to empower growers to make well informed management decisions in dealing with the issue of harmful smoke taint compounds being discovered in this year's grapes and wine.

"If successful, the initiative will not only be a world-first, it will contribute significantly to the national wine industry's knowledge base and understanding of a complex viticultural challenge that has been a concern in Australia for more than 15 years," said renowned Victorian researcher and smoke taint expert, Professor Ian Porter.

Tasmanian growers have no illusions regarding the changing viticultural risk factors they now operate under in the State. Despite their island's relatively high southern latitude and cool temperate growing conditions, wine producers have had to come to terms with the threat of uncontrolled bushfire activity with ever-increasing frequency over the past five or six years.

A University of Tasmania study published in the academic journal Fire in October 2018 shed new light on the extent of these alarming developments. Researchers examined historic fire data collected by the Tasmanian Parks and Wildlife Service from 1980 to 2016. They found that while less than a handful of wilderness fires were caused by lightning strikes during the 1980s and 1990s, almost 20 were recorded in 2015-16. A marked overall increase in lightning-related fires since 2000 was also associated with significant increases in the average size and intensity of wilderness blazes.

Fires closer to more populated parts of the State also appear to be on the rise.

During summer 2016, a handful of growers in northern Tasmania were fortunate to avoid damage to their grapes and wine when bushfire smoke elevated levels of many of the volatile phenols known to contribute to smoke taint. Those most at risk were small vineyard operators in and around the Tamar Valley, where temperature inversion is a common atmospheric phenomenon for much of the year.

Unlike the fires that razed Dunalley on Tasmania's south-east coast in January 2013, this year's bushfire activity unfolded relatively slowly. During the last week of the State's third warmest December on record, dry lightning strikes ignited fires around Great Lake in the Central Highlands and at Gell River in southwest Tasmania.

By mid-January, uncontrolled fires were being fought on a range of fronts, including multiple sites in the Tasmanian Wilderness World Heritage Area, on the West Coast, and in highly prized eucalypt forests located on the margins of southern Tasmania's Huon Valley and D'Entrecasteaux Channel winegrowing districts. Between them, the latter represent around 5% of the State's total vineyard area.

The gamechanger had been an intense period of thunderstorm activity on January 14, when more than 1500 dry lightning strikes overnight were followed by a further 500 strikes between 9:00am and 12:00 the next day. These were to result in more than 60 new bushfires being logged by the Tasmanian Fire Service.

The rapidly escalating threat to vineyards brought swift responses from industry players on both sides of Bass Strait. For Winemaking Tasmania chief winemaker Glenn James, the gathering storm had an all too familiar ring to it. The one-time Treasury Wine Estates Group Winemaker had had previous first-hand experience with vineyards interstate that had been exposed to high levels of bushfire smoke.

In mid-February, James's employer threw open the doors of its contract winemaking operation near Hobart Airport to welcome producers from across the State to a special information session on smoke taint. Sharing the podium with James were Con Simos, AWRI Group Manager (Industry Development and Support); Mark Krstic, AWRI Business Development Manager; and renowned La Trobe University smoke taint researcher, Professor Ian Porter.

The presenters had spent the previous fortnight working at breakneck speed to formulate a carefully devised and well modulated set of industry responses to grower concerns. Porter, for example, had worked quickly with growers to set up smoke monitoring equipment which accurately measured the levels of smoke at vineyards at risk from the fires burning in critical Huon Valley hotspots around Geeveston and those further south, at Dover. This was then used to provide growers with an early prediction of smoke taint risk in the vineyards.

In contrast to previous assignments used elsewhere in Australia, this time the project team had additional, more widespread analytical data at his disposal.

"Tasmania is the only place in the country that has a Statewide air quality monitoring program that can provide widespread real-time particle concentration data from a network of over 30 air quality monitoring stations," Porter explained.

Established in 2008 by EPA Tasmania as a State Government response to community concern over air pollution caused in winter by domestic wood heaters, the network has proved to be equally valuable in monitoring levels of air quality during controlled burns and bushfires. Particulate matter data for PM10 (10 micrometre or less in diameter) and PM2.5 (2.5 micrometres or less) obtained from this Base Line Air Network of EPA Tasmania (BLANkET) are readily available online. The network also contributes to archived data records stretching back over a decade.

BLANkET data courtesy Dr John Innis, EPA Tasmania.

"Our first task in Tasmania was to validate if the air quality monitoring network data could be translated into useful smoke information being recorded for the same sites," Porter said.

"The fact that our data did line up is already a major outcome for the industry. Further research in coming months should enable us to work out if EPA Tasmania's air quality data will be useful to act as an early warning system for growers around the State."

Porter's fieldwork will also contribute to what James and his team at Winemaking Tasmania believe is a world's best practice framework for addressing sensory and scientific assessments of potential smoke taint that can be applied to vineyards deemed to have been exposed to significant smoke risk.

"The framework comprises four independent components, which when collated, will provide the best available information to make informed judgements on the likely presence and effect of smoke taint on grapes suspected of being affected by elevated levels of volatile smoke taint compounds," James told briefing invitees.

The component parts include conduct of micro-ferments in Tasmania using representative samples of wine grapes with pre-harvest maturity between 8.0°Be and 11.0°Be. These are to be sourced from vines deemed to have been at risk from smoke taint compounds. Following fermentation to dryness, the resulting wines will be tasted and assessed by a panel of experienced local winemakers familiar with the olfactory characteristics typically displayed by smoke tainted wines.

A further 500 gram sample of fruit is to be frozen at Winemaking Tasmania's Cambridge facility and couriered overnight to the Australian Wine Research Institute's Commercial Services laboratory in Adelaide. There, rigorous testing and analysis in conjunction with a control batch of unaffected grapes will establish whether or not threshold levels are exceeded for as many as seven different smoke taint compounds present in the sample.

Finally, a third frozen sample is to be sent to Melbourne for testing by the team at La Trobe University/Agriculture Victoria, using a less time sensitive but no less valuable method to accumulate data on smoke taint in grapes and wine.

Porter says this summer's events in Tasmania are likely to provide a watershed moment for those engaged in national and international investigations of smoke taint, by highlighting further avenues of research to be explored in the future. It will be highly important that the current work funded through the Federal Department of Agriculture and Water Resources Rural R&D for Profit program continues.

"The bushfires in Tasmania represent one of only a few times in Australia we've had access to statistically significant, correlated air quality data and extensive vineyard data for events of this nature," Porter noted.

"Generally, by the time we get to a bushfire it's already been going for 2-3 days, making it difficult to get reliable fresh smoke data. The program being undertaken should prove a godsend to producers, as it will provide us with a sound basis from which we can expand our understanding and better predict likely outcomes from the smoke generated from future fires."

First published April 2019: Australian & New Zealand Grapegrower & Winemaker, Issue 663