Saturday, December 18, 2010

Facing the hard local realities of a warming world

 Michael Bachelard 
Sunday Age, December 19, 2010
CLIMATE change has done Nat White a big favour. It has provided his boutique Mornington Peninsula vineyard with the perfect conditions for growing pinot noir and chardonnay.
Warmer temperatures in the hills that run down the spine of the Mornington Peninsula mean Mr White is now virtually assured that his grapes will ripen every year, even though he is harvesting them a full month earlier than he did in 1975.
This is just one of dozens of changes that warmer, drier conditions have already wrought in Victoria.
Lower average rainfall means that the water table has shrunk deeper underground, easing the threat of salinity; crops such as wheat can now be grown reliably in Victoria's Western District, formerly mainly suitable for livestock; populations of birds, frogs and butterflies have plummeted or changed their behaviour; trees native to Victoria are struggling and people in cities and towns are suffering more heatwaves and bushfire-threat days.
Across Victoria, the climate is changing - not just in models of the future but also in observed events. These have already altered the landscape, forcing us to change the way we interact with it. This process has created both winners and losers.
Victoria University professor Roger Jones said these changes all flow back to two facts: maximum daily temperatures have risen almost 1 degree on average in the past 14 years, while average annual rainfall has dropped 15 per cent in that time.
This year, Professor Jones said, a rare conjunction of climatic events had dumped a lot of tropical rain on Victoria, something that last happened in 1975. The ''general meteorological view'' is that this season, unfortunately, is a ''blip'' that is unlikely to be repeated soon.
Averages also mask vastly different regional effects. Stream flows in south-east Australia are down 44 per cent on average, but the drier, warmer soil and reduced autumn rainfall means reductions of up to 86 per cent in some catchments.
''These changes are highly significant,'' Professor Jones said.
''People assume that historical climate is stationary and climate change will be gradual but what we're seeing isn't a trend … it's a step change … a change of state.''
Every climate model shows an abrupt shift for this part of the world, he said.
Nat White, who has been growing the same grapes on the same land since 1975, finds this change of state suits him well. In the old days his grapes were not ready for picking until late April, even early May. But in some years it was too cold and difficult to ripen them.
Now, with good rainfall in his corner of Victoria and warmer weather, the harvest is reliably a month earlier. ''We've come into what I think is a fairly optimum condition from a condition that was really too marginal.''
On the downside, the warmer weather is accelerating the production of sugar, which is in danger of outpacing the development of flavour in the grapes. ''If you get too much sugar you get a higher alcohol content, and it gets out of balance,'' he said.
But the change that has favoured Mr White's operation has devastated some vineyards in the north of the state. Melbourne University professor Snow Barlow said some winemakers had closed, while others were investigating introducing Sicilian or Spanish grapes that are adapted to dry heat.
Corporate winemakers such as Brown Brothers and Foster's were busy buying land in Tasmania to grow their chardonnay grapes. Other crop growers have also been forced to adapt to the changing conditions.
Derrimut wheat was bred for the dry, hot Wimmera region. But now John Hamilton, and dozens of other farmers, are growing it south of the Dividing Range. His farm is near Geelong, where it has previously been too wet and cold for wheat. ''There's no doubt that it's happening across the region; not just our farm,'' Mr Hamilton said.
Two decades ago, farms in his area west of Geelong had 60 per cent stock and 40 per cent crops. ''Now I'm 95 per cent crops,'' he said.
A similar move is happening in Gippsland, in the state's south-east.
Meanwhile, in the Mallee region, the hot, dry conditions until this year have increased the stress on plants, making farming more difficult. Dairying has also been forced south.
The Birchip Cropping Group was set up by farmers in the Wimmera-Mallee to help them navigate these changes. But agronomist Harm van Rees says farmers in the north have few alternatives for adaptation.
''In the Mallee it's been very difficult to see what farmers can do other than grow the traditional crops and run their livestock,'' he said.
Some farmers are buying land in the south as insurance or so they can move stock between properties.
Professor Jones said the Wimmera had ''the smallest, most exposed economy to climate change'', with 30 per cent of its income exposed to highly climate-sensitive industries. The Mallee was not far behind.
Victoria has traditionally been a hugely productive orchard, but that too has changed, ''driven'', in the words of John Wilson of Fruit Growers Victoria, ''totally by lack of water''.
Science is reinventing the shape of fruit trees: they are smaller so they spend less energy on growing wood and more on growing fruit; they are planted 40 times more densely; and they are productive within four years rather than 10.
But increasing temperatures are also changing fruit behaviour. Mr Wilson said that two years ago the Gala apples failed supermarket specifications because the nights were not cold enough to produce the typical red, stripey colour.
Scientist Rebecca Darbyshire says apple trees need at least 100 very cold nights in winter to ensure proper fruit in the next season. At Tatura, near Shepparton, the number of cold nights has fallen from 150 to 120. It's not enough to have an effect, but it's a worrying trend.
Hot weather is also affecting forestry operations, with Rowan Reid, co-ordinator of the Australian Master TreeGrower Program and a former academic, noticing that trees such as shining gum, which have adapted to Victoria, are suffering because of hot, dry conditions. ''We're growing dryland species like red ironbark in high rainfall areas now because of climate uncertainty and higher temperatures,'' he said.
Salinity, on the other hand, has improved markedly, says Greg Hoxley of consultant SKM.
Water tables rise as a result of excess water collecting on the surface when thirsty plants such as trees are replaced by crops. With drier conditions, water tables are sinking again.
''It's a topic of active consideration as to whether saline areas will need to be actively managed to the extent they were a decade ago,'' Mr Hoxley said.
The story of agriculture in Victoria is of adaptation to change: shifting where crops are grown, developing new varieties or methods.
But some birds and animals will find it hard to adapt. Of the 108 woodland bird species in central Victoria studied by Deakin University scientist Andrew Bennett, two-thirds had declined significantly over the years of drought to 2007.
Much of the decline, seen among both insect-eating and nectar-eating birds, was driven by the failure of the red ironbark trees to flower over four successive seasons.
Another study showed frogs decimated by the hot, dry weather, with a team led by Monash University professor Ralph Mac Nally observing in 2006-07 that fewer than half the species expected in areas of central Victoria were still surviving. In Victoria's redgum forests, 65 per cent of the trees are now in poor condition.
Scientists are eager to establish whether this year's big wet will re-establish some of the populations of birds, frogs or trees, or whether too much damage has already been done.
Climate changes are also beginning to affect human settlement patterns.
The Victorian Civil and Administrative Tribunal has rejected two coastal developments - one in Lakes Entrance and one near Wilsons Promontory - for fear of inundation by bigger, more frequent storms.
And councils, starting with Wodonga, are developing heatwave plans to move vulnerable groups to cooler areas if necessary. Deaths increased in Melbourne during the late-January heatwave of 2009.
According to Professor Jones, Victoria's climate is already variable, but his work shows that ''if you force it [with human-induced factors], it will be even more variable''.
The change in Victoria's climate happened 12 or 13 years ago and the result is ''extreme events that are unprecedented in the historical record''.
The results can now be measured in dozens, perhaps hundreds of shifts in environment and behaviour.
''The changes will require a significant planning response,'' Professor Jones says, ''and nobody should underestimate the risks''.

 

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