Hotter, harder times forecast for the farm as climate changes food production

A warming, largely drying climate for a range of foods from almonds to zuchinis has been identified by the The Appetite for Change study, finding few likely winners.

"Food production in Australia will need to adapt to the inevitable impacts of climate change," said Richard Eckard, an associate professor. "But there are limits to the temperatures and extreme weather events that farmers will be able to adapt to."

For farm animals, the main impact may be caused by heatwaves, which are anticipated to become more intense, more frequent and last longer. According to the latest research by the CSIRO and the Bureau of Meteorology, the number of extreme heat versus extreme cool daily records since 2001 is running three-to-one for maximums and five-to-one for minimums.

"In a heat event, they all suffer heat stress," said Professor Eckard, who is also director of the Primary Industries Climate Challenges Centre, a joint venture between Melbourne University and the Victorian government.

Belying the phrase, "sweating like a pig", these animals don't have sweat glands are particularly sensitive to heat. As evidence of their vulnerability, about 500 pigs reportedly died at a piggery near the NSW Riverina town of Grong Grong one weekend last month when a ventilation system failed.

A long-term reduction of winter rains in south-western and south-eastern Australia is already forcing farmers to adjust their crop varieties to suit an often shorter planting season, Professor Eckard said.

Australia's average temperatures have increased 0.9 degrees since 1910, with the rise of greenhouse gases contributing to the warming, the CSIRO and the bureau said. By 2030, temperatures will increase by 0.6-1.3 degrees on 1986-2005 averages, and as much as 5.1 degrees by 2090 if emissions remain on a high trajectory of growth.

For crops especially sensitive to heat, such as blueberries or raspberries,the shift is likely to be to the cooler regions of Victoria, southern NSW and Tasmania.

As much as 70 per cent of the wine-growing regions with a Mediterranean climate – such the Barossa Valley in South Australia and Victoria's Sunraysia – will be less suitable for grape growing by 2050. Red varieties such as shiraz and merlot will be among the most affected.

Whereas rising carbon dioxide levels assists plant growth – the so-called fertilisation effect – the benefits are curtailed if there is insufficient water, phosphorous, nitrogen and other nutrients. Wheat, for instance, may increase in quantity but have lower levels of protein.

"You get nothing for nothing in nature," Professor Eckard said.

Warmer temperatures may extend the range of areas suitable to grow olive trees, with eggplants and mangoes among the crops likely to be grown further south than today. Crops needing exposure to winter chill for regrowth, such as peaches, will see a shrinking range, although impacts in Tasmania are expected to be minimal.

Banana plantations are concentrated in north-east Queensland, leaving them exposed to cyclone strikes, such as from Cyclone Yasi in 2011. Cyclones may become less frequent but more intense, according to climate studies.

Growing bananas elsewhere has its risks too, as shown by the widespread destruction of plantations near Carnarvon in Western Australia by this week's Cyclone Olwyn.

Despite farming generating some $48 billion in 2012-13 and already exposed to Australia's famously fickle climate, the Abbott government's green paper on agricultural competition published in December omitted any mention of climate change.

"The federal government's really behind the eight-ball on this because they are playing politics," Professor Eckard said. "If you can disentangle climate change from the politics, we'd be so much better off."

The Appetite for Change report's release marks the launch of Earth Hour, in which millions of people in 160 nations are expected to switch off their lights for 60 minutes. This year's event kicks off at 8.30 pm, AEDT, of Sunday, March 28.

'Short droughts'

Predictions that beef production in southern Australia will face significant challenges with climate change ring true for Derek Blomfield.

His third-generation family farm, Colorado, runs about 250 head of cattle on almost 1000 hectares at Quirindi on the fertile black soils of the Liverpool Plains of northern NSW.

For the past three years, Mr Blomfield has had to cope with what he calls "short droughts", periods of three or four months with little rain, broken by one or two big rain events.

The result is rapid, intermittent bursts of pasture growth that must be cut rather than grazed.

"It's almost like you have to store it away and treat it like a hayshed," Mr Blomfield said. "In the past, [the rain] was more consistent and more reliable."

The Liverpool Plains region is expected to warm on average about 0.6-1.2 degrees by 2030 on 1980-99 averages, according to the Appetite for Change report. By 2070, temperatures may be 4 degrees warmer if a high-emissions trajectory is maintained.

Dairy cows are known to produce less milk in hot temperatures with their "pant rate" rising as animals try to lose heat, leaving them less time to eat.

For beef cattle, Mr Blomfield has observed his animals head for shade and begin ruminating earlier in the day during hot stints, cutting grazing and delaying the time it takes them to reach target weights.

Warmer nights, another trend already widely observed across Australia, can also affect pasture and crop growth. "If it's warmer at night, those plants don't get to recover fully ahead of the next day's growth," Mr Blomfield said.

Foods affected include:

Beetroot: temps above 27C potentially causes bolting - early running to seed

Carrots: grow best at 15-18C, with flavour and texture affected above that.

Chickpeas: temps above 35C during flowering cuts yield

Dairy: heatwave stress cuts milk output in cows by as much as 40%

Lemons: optimal temps 25-30C, with fruit shed early at 37C or warmer

Potatoes: 'late blight', source of Irish famine in 1840s, more likely with high temps, humidity

Salmon: optimal temps 7-17C; east coast waters warming fastest in Southern Hemisphere, potentially reducing range

Sugar cane: optimal growth range 32-38C, with less sugar accumulated above that

Zucchini: susceptible to extreme heat, drought intolerant