Adaptation key to climate change, says Tasmanian modellers

The NEXUS Project is using social research, biophysical and economic modelling to examine the impact of climate change to 2030 and 2050 on livestock businesses in Tasmania.

"Relative to the mainland, Tasmania - particularly the north-west coast - is in a better position, there is no question about that," NEXUS lead researcher Associate Professor Matthew Harrison said.

"But in the south-west, areas like Swansea and Triabunna will struggle

"They will certainly be hotter and the frequency of droughts will be more common."

Assoc Prof Harrison said the NEXUS team was modelling gas emissions (methane, nitrous oxide and CO2), profitability and productivity on two Tasmanian farms.

"We are modelling all of the aspects (of climate change)," Assoc Prof Harrison said.

"We are accounting for animal numbers, pasture and soil type, species, and historical climate."

NEXUS researchers were looking at how a beef farm at Stanley, in the north-west, and in a large sheep property in the Midlands would perform in 2030 and 2050 under more extreme climate conditions and weather events.

He said the team had used an "ensemble" of about 30 different climate models from around the world.

Averaged annually and across the farms, the majority of global circulation models (GCMs) within the ensemble showed 2030 temperatures would be 0.5-1.5C warmer, with little change in rainfall (-5 to +5 per cent).

For 2050, annual average temperatures would be 1.5-3C warmer with a -5 to -15pc reduction in rainfall.

"These projections were built using the emissions scenario called 'Representative Concentration Pathways 8.5' (commonly RCP8.5) - this is the most severe climate projection and most closely represents the trajectory that global climate change is currently tracking."

While the initial evidence was positive, farmers would still need to adapt to maintain

"Temperatures are going up, atmospheric C02 is going up and variability, particularly in the Midland, is increasing.

"So how do those two systems perform under future climates?"

Assoc Professor Harrison said initially pasture production, in both regions, would improve.

"'Winter pasture growth rates increase a bit because temperatures are warmer and atmospheric C02 is higher, so that has a fertilisation effect.

"But when we go out to 2050 the opposite is the case - pasture production is starting to decline

"As above ground dry matter decreases, particularly in the Midlands, your ability to sequester carbon is also declining."

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Early evidence suggested increasing legumes in the pastures was one simple way of adapting to climate change.

Lucerne had a deeper tap root than the perennial ryegrass it was replacing, increasing soil carbon.

'It's almost a win, win, win," Assoc Prof Harrison said.

'The warmer climates are more conducive to reducing lamb mortality and improved productivity, the lucerne is improving live weight gain because of its digestibility and soil carbon has increased because you have a taproot of a legume that is going down deeper than the perennial ryegrass that it's replaced."

But he said farmers could not afford to become complacent.

"The other important message is that productivity doesn't necessarily translate to profitability".

Detailed economic modelling showed even if productivity was the same, producers faced what economists called a "cost-price squeeze" of about one per cent a year.

"Costs for hay, grain, labour, repairs and other inputs are all going up by about 1pc a year," he said.

"To keep pace with that change, you have to improve your profitability by 1pc - even in the absence of climate change you still have market and price changes."

NEXUS researchers were also looking at renewable energy and income diversification, to buffer against drought.

"One farmer is thinking about a cherry orchard, he has mapped the ideal microclimate on his farm and where he is going to plant this orchard.

"If, for example, he gets a very bad year and it doesn't rain, and the pasture doesn't grow, he will still get income from his cherries."

He said farmers should be concerned about climate change.

"The reason they should bother is that by 2050, the climate will intensify, pasture production will go down - particularly at the shoulders of the seasons in autumn and spring.

"With an ongoing cost-price squeeze it's going to become harder and harder to remain prosperous.

"If you don't adapt, you are going to get left behind."