Impacts on dairy

Impacts on dairy farming

To meet the challenges of climate change, Dairy Australia commissioned the CSIRO to examine the potential impacts across all Australian dairy regions. The projections are relative to the ‘average’ of the 20 year period 1980-1999. Importantly, the project did not include projections on increased climate variability. Climate variability is predicted to increase, and this is clearly a major concern for dairy farmers, but there are no reliable predictions of how variability might change or by how much.

Summary of CSIRO report:

Predictions for all dairy regions are warmer and drier, with increased evaporation and less runoff. Increased seasonal variability and extreme weather could make it more challenging for dairy animals and more difficult or expensive to grow quality pasture or supplementary feed. This will be amplified if access to irrigation water is further reduced. Dairy Australia’s “Diarying for Tomorrow program” has prepared regional fact sheets based on the CSIRO report:

Please note - these are pdf files, they may take a few seconds to open.

Western VIC
Gippsland
Northern VIC and southern NSW
North-east VIC
Tasmania
NSW
Northern NSW
WA
Central SA
South-east SA

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Impacts on Cows

Dairy Australia’s Cool Cows web site gives advice on how to prevent and manage heat stress, which is already a significant challenge on many Australian dairy farms.

Cows have evolved a range of mechanisms to off-load heat, but problems can occur if temperatures and humidity remain high. At temperatures above25°C, cow begins to feel uncomfortable, reducing their ability to produce milk and get in calf - health and welfare may also be affected. Provision of shade, minimising the distances walked, and active cooling by sprays are important heat stress management tools. The increase in metabolic activity associated with high milk yields has added to the heat stress dairy farmers must manage in their herds.

The impact of climate change on cattle differs between breeds. Tropical breeds like the Brahman cope better with heat than European breeds, partly because European breeds must evaporate more sweat in order to maintain normal body temperatures. Of the European dairy breeds, Brown Swiss and Jersey are least vulnerable to heat stress, then Ayrshire and Guernseys, followed by the Holstein-Friesian.

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Impacts on Pasture

Depending on their dairy region, the following are some of the general pasture impacts farmers might see as a result of climate change:

• Winters will be warmer with fewer frosts. Pasture growth rates could be higher in winter in southern dairy regions, and using nitrogen fertiliser during winter may become more effective
• Summer will be hotter, beginning earlier and finishing later – potentially causing heat/moisture stress over summer, while shortening the peak of spring growth and delaying the start of ‘autumn’. Short rotation pasture systems and winter fodder crops may become more attractive than irrigating pasture over summer
• Increased temperatures may make C4 pasture species like paspalum, kikuyu, maize and forage sorghum more competitive at the expense of the nutritious C3 species like ryegrasses.
• Irrigation requirements will increase with higher temperatures and lower rainfall. Irrigation availability is likely to decrease, magnifying the impact on pasture production.

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As part of the Southern Livestock Adaptation program modellers at the University of Melbourne have developed a mechanism to examine how for any location, changes in temperature and rainfall could affect pasture production. The two examples below are for Ellinbank in Gippsland and Elliot in NW Tasmania. The graphs are a little difficult to understand at first, but the starting point (the average pasture growth from 1970 to 2000) is shown, and the 3D graph then plots all the possibilities associated with from a 10% increase to a 30% decrease in rainfall and from a 0 to 4 degree rise in temperature (none of the climate models predict a decrease in temperature!).

The dotted lines (oval shapes) indicate the current predictions for 2030, 2050 and 2070. In contrast to the likely significant decline in pasture production at Ellinbank where increasing rainfall is the major threat, Elliot is predicted to increase pasture production under most scenarios even out to 2070 – at Elliot, declining rainfall is the major threat to pasture production.

 
 

Impacts on farm water supplies

Climate change projections indicate farm water supplies will decrease due to lower rainfall, higher evaporation, changes in seasonal patterns and more frequent/longer droughts. These factors generally cause run-off to be reduced at more than double the rate of rainfall reduction. Farmers who rely on surface run-off for irrigation or dairy supplies could face more severe water shortages. However, run-off estimates are not always reliable because run-off depends on timing and intensity of rainfall as well as rainfall amount.

If there is less rainfall/run-off, then reductions in the reliability of supply will vary but they are likely to be greatest where surface water use is already high, and where climate change is predicted to have the largest impact on water availability. In the Murray-Darling Basin this would be the Murray, Goulburn-Broken, Campaspe, Loddon-Avoca and Wimmera regions.

By 2030 predictions, the availability of surface water in the Murray-Darling Basin will reduce by an average of 11 percent, 9 percent in the north of the Basin and 13 per cent in the south.

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References and resources

Climate Change in Australian Dairy Regions, Hennessy, K.J., 2007 is available on the Dairying for Tomorrow website.

Eckard, R., Cullen, B. and Snow, V. (2008) WFSAT Phase II: Final Report: Whole Farms Systems Analysis and Tools for the Australian and New Zealand Grazing Industries.

Cool Cows website.

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