Securing water is the number-one priority for any viticultural venture and the lack of it is one of the threats with a changing climate.
IN most workplaces we are told that we must adapt and be comfortable in a “change environment”. The fast moving pace of life affects everything we do. And the same can also be said about the profession of growing grapes. Climate change, seen through challenging growing conditions, is forcing viticulturists to constantly question their approach to growing healthy grapes. Global warming is becoming one of the key factors that is driving what kind of wines we drink.
South Australia is regarded, rightly so, as the “Wine State” and it is at the forefront of producing the volume that we will need to satisfy the booming Chinese market. In a speech at the 2019 Australian Wine Industry Technical Conference, wine industry heavyweight Warren Randall, chairman of the Randall Group, said the rise of “China’s middle class – the consuming class – is exploding”. It will be this market that will provide the challenge for Australia as “we will not have enough wine to satisfy China’s thirst,” commented Randall. Such is the optimism for future exports that there is a gold rush feeling about the industry at present. Randall is racing to meet the expected demand. Not only does he own Barossa Valley’s Seppeltsfield Estate as well as the premium bulk wine company Tinlins, he has Ryecroft Wines in McLaren Vale and Quelltaler Estate in the Clare, where this year he purchased over 300ha of farmland to plant more vineyards.
So to try and prepare for this explosion of demand for South Australian premium grapes, producers like Randall, are looking at alternative ways of supplying water to them. Securing water is the number-one priority for any viticultural venture and the lack of it is one of the threats with a changing climate. With the relentless pressure on the Murray Darling system, grape producers are looking at other sources. Using desalination/reverse osmosis units to filter out salts in underground water that would normally be too saline for irrigation, is one measure being used. Instead of filling dams with water and suffering evaporation, some producers are using underground aquafers as a massive storage tank as another measure. It’s a technique known as ASR (Aquifer Storage and Recovery) In the Barossa Valley there is now a system of pipes and dams that supply storm water from the Gawler River. Because the river is dry an average of three out of 10 years Adelaide treated and recycled grey water from the Bolivar treatment facility is used as a supplementary supply.
Once you have the water you then have to use it judiciously. In a climate change environment understanding the terroir of a site and adapting the use of resources is critical. “Soil moisture monitoring is essential so you can irrigate with optimum efficiency,” comments wine business consultant and Master of Wine Phil Reedman. “In hot climates, ideally, the soil’s water holding capacity is sufficient that you can water at night to lessen the effects of evaporation. Whereas, in the Riverland region, many of the soils are so free draining that they have no water retention holding capacity and therefore need water applying when the vine needs it most, which unfortunately is during the day.” “Irrigating in winter when the vine is dormant or early spring might sound dumb but the idea is to top up the winter rainfall and get the water deep into the soil so the roots can draw upon it during the growing season,” he said. Investing in deep mulch, straw or cover crops is also vital in protecting the soil from losing its moisture.
The impact of global warming is also evident in the rapid physiological ripening of the grapes and often means the harvest period is short and frantic. It also explains partially why Clare Valley riesling tastes different from riesling grapes grown, in say, the Mosel in Germany. To get ripe skins and stalks you need a long hang time, in other words a long, dry autumn where the grapes slowly ripen. With hotter temperatures ripeness happens quickly with decrease in acidity and increase in sugar. The grapes must be picked before their baume level becomes too high to produce a balanced, fresh, light-bodied style of riesling. Retention of natural acidity is preferred over having to add acid in the winery. Riesling grapes contain tart natural malic as well as tartaric acid. Sam Barry, from Jim Barry Wines, explained this on a tour of his family vineyards. “In the Clare malic acid quickly burns off during the day in the hot weather, so Clare rieslings have low levels of malic and a high level of tartaric acid,” he said. “But in the Mosel it retains it a lot better and therefore you get a different acid profile between the two wines.” Having that higher level of malic acid gives the German wines their racy, green apple flavours as well as being used to hide residual sugar which helps build texture and complexity.
Grafting over or planting varieties that are better suited to climate change is the most direct way of facing the problem and can be a profitable way forward. Varieties like vermentino and nero d’avola have the right attributes to handle the heat and are drought tolerant. Travelling around South Australia you soon get to realise these “new” varieties are making their mark. Negroamaro and touriga nacional are also on the rise for the same reasons. The Greek white assyrtiko is being pioneered by Jim Barry Wines and if there is one grape variety that can stand a drought it is this one. It originates from the island of Santorini which doesn’t see rainfall for eight months of the year. In our fair dinkum Aussie tradition of shortening words, nero d’avola is simply being labelled as “nero”. In the hot spikes that have been experienced in South Australia in recent summers these Mediterranean varieties continue respiration and photosynthesis at high temperatures, while other traditional grape varieties shut down. Fortunately for South Australia our traditional grenache is already equipped to deal with the heat and is experiencing a welcome renaissance.