Understanding climate impacts

 

Climate change increases the variability of temperature and rain patterns. In addition, a whole range of extreme events, such as floods, droughts and heat waves and associated risks such as price volatility, pests and diseases become more likely.

Dairy farmers have already seen the impacts of climate change on their businesses:

  • In Gippsland & Northern Victoria, pasture growth patterns have changed, spring now starts about four weeks earlier.

  • In the Northern Irrigation Area, reduced water availability has favoured annual pastures over perennial pastures. Farmers are investigating pastures such as lucerne, which have deeper root systems and can tolerate longer periods of water deficiency.

  • In South Australia, in response to more competitive land and water use, as well as reduced availability and quality of water, some farmers are already making changes to their systems, while others are relocating.

Adapting and building resilience to a changing climate needs to take into account the unique economic, social and environmental pressures each dairy business faces. Consequently, the planning of a climate-ready dairy business requires an understanding future climate projections and their potential impact across the business. All practices and responses can then be evidence-based and context-specific.

  • Impacts on dairy farming

    While current climate change projections, based on averages, pose only a limited threat to many dairy regions, the main impact for most dairy farms will be through increased climate variability.

    Extreme weather events (such as flooding, bush fire, droughts, failed spring conditions, wet winters, wind storms) will increase in frequency and intensity in the future.

    Dryland dairy businesses that currently rely on summer pasture/crop growth may face difficulties into the future as warmer and drier climate scenarios are predicted to change the seasonal pattern of pasture production. Winter and early spring pasture growth rates are predicted to increase, but the length of the growing season is predicted to shorten.

    Wealth, learning and formal education, and availability of adaptation options are key factors influencing climate-related adaptive farm management

    CSIRO 2007 Report - 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.

  • Impacts on cows

    Dairy Australia’s Cool Cows website 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. Heat load accumulation can occur when hot nights do not allow animals to recover. At temperatures above 25°C, cow begins to feel uncomfortable, reducing their ability to produce milk and get in calf - health and welfare may also be affected. 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.

  • Impacts on pasture

    Future warmer and drier climate scenarios will alter the balance between the productivity and persistence of perennial grasses to support livestock production systems (Cullen et al).  Heat tolerance and rooting depth are key factors and will influence farmer’ choice of species. 

    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.

    The impact of climate scenarios will affect regions differently:

    • Those regions that are currently hot and dry (e.g. Moree and Wagga Wagga) will remain so, but existing pasture types at this location based on a mix of C3 and C4 species appears to be quite resilient to the changes in climate.

    • In other regions, hotter and drier conditions are likely to challenge the productivity and persistence of current pasture species, particularly where the current species are near the edge of their adaptive range (e.g. perennial ryegrass based pastures at Hamilton and Terang in south-west Victoria).

    • In a cool temperate site such as Elliott, perennial ryegrass production will increase in warmer and drier scenarios and its benefits in ease of management are likely to see it continue to be widely used.  However as the climate becomes warmer and drier, deeper rooted options such as tall fescue and phalaris may be integrated into the systems.

    • Overall, increasing numbers of hot and dry days will challenge persistence shallow rooted perennial grasses such as ryegrass.  This will tend to favour the summer dormant species such as phalaris, however the tradeoff between the ease of management of ryegrass with the persistence benefits of phalaris is likely to be amplified in many regions of southern Australia.

    • Kikuyu is very reliant on summer rainfall to grow, so its production is highly susceptible to rainfall decline.  In addition low winter production will limit its adoption as feed grown through this period is valued a lot higher by farmers.

  • 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.

  • Impacts on biosecurity
    Future climate changes will influence the spread of livestock and pasture pest, disease and weeds.