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Impacts on agriculture

Background

While there is a growing consensus on the causes and likelihood of climate change, there is uncertainty about the impacts across the agricultural sector. Given that predictions are for a hotter, drier South and wetter North, the impacts will likely be complex, and vary by commodity and region.

For agriculture, climate change is expected to affect productivity through increased temperatures, changed rainfall patterns, increased levels of carbon dioxide and increased climate variability. There may also be indirect effects through changes in diseases and pests, and increased rates of soil erosion/degradation.

Changes to agricultural policies could also impact on agriculture. The Department of Climate Change has characterised Australian agriculture in to four sub-sectors (see below), and has summarised likely climate change impacts (potential policy action on emissions not included):

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Impacts on intensive livestock

(pigs, poultry and some dairy)

  • Increased heat stress and/or cooling costs
  • Increased incidence of pests and diseases requiring increased health and welfare efforts
  • Reduced feed supplies from lower ‘home grown’ yields and reduced availability/ increased prices of grain for purchase
  • Reduced availability, reliability and quality of stock water supplies

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Impacts on extensive livestock

(beef cattle, sheep and some dairy)

  • Increased heat stress
  • Increased animal health and husbandry challenges
  • Reduced reliability and quality of water supply to stock
  • Reduced carrying capacity (or increased risk at the same carrying capacity) due lower reliability of pasture supplies
  • Reduced pasture production (an increase in winter growth but countered by declines in most other seasons)
  • Changes to the dynamics of pasture pests, diseases and weeds requiring increased management input
  • Reduced herbage quality, both from an increased number of dry spells, and from the incursion of C4 (sub-tropical) grasses into pastures currently dominated by the higher quality C3 (temperate) species
  • Increased potential for soil erosion and nutrient movement into waterways due to more common dry periods and feed shortages leading to overgrazing

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Impacts on extensive cropping

(cereals, oilseeds and grain legumes)

The overall impact on extensive cropping is likely to be negative, though there are a mix of possible gains and losses:

  • Reduced soil moisture due to lower rainfall and higher evaporation rates – a negative for most cropping areas, but a positive in higher rainfall areas due to decreased soil water logging
  • Increased winter growth rates when soil moisture is adequate
  • Increased heat stress on top of any increase in moisture stress
  • Increased variability and changes to seasonality of rainfall – later autumn breaks, lower rainfall in winter and spring, and increased incidence of drought all reduce average yields and increase the risks associated with cropping systems
  • Changes to the incidence and dynamics of pests, diseases and weeds
  • Reduced grain quality and/or nutrient content reducing returns
  • Increased demand for grain to meet the requirements of a growing world population (and for livestock feeding) and the fact that cropping produces significantly less greenhouse gas than livestock per kilojoule of food energy could mean higher prices

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Impacts on intensive cropping

(horticulture and viticulture)

  • Reduced soil moisture from the combination of lower rainfall and higher evaporation rates providing negative (drought or increased irrigation requirements) and positive (less waterlogging) outcomes
  • Decreased frost frequency – positive for frost sensitive crops, negative for vernalisation requirements
  • Changes to optimum sowing and harvesting times which may or may not suit marketing requirements
  • Increased irrigation requirement despite reduced supply and increased demand from other irrigation industries, urban users and the environment
  • Altered range and incidence of pests and diseases, requiring increased management and possibly chemical input
  • Reduced product quality (nutritional, appearance due to water / temp stress, and increased CO2 concentrations)
  • Increased demand due to lower supplies and increased populations could mean higher prices

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Impacts on agricultural policies

The Australian Government commissioned CSIRO and the Bureau of Meteorology to examine how the current regulations for drought and exceptional circumstances would be affected by climate change. The project reported that:

  • The extent and frequency of exceptionally hot years have been increasing rapidly over recent decades and this trend is expected to continue
  • By 2040, what we now consider exceptionally high temperatures are likely to occur every 1-2 years
  • If rainfall was the sole trigger for EC declarations, then the mean projections for 2010-2040 indicate that more declarations would be likely, and over larger areas in SA, SW of WA and the Vic & Tas regions, with little detectable change in the other regions
  • If soil moisture were the sole trigger for EC declarations then declarations would be more frequent than for a rainfall only trigger – for the high climate change scenario, EC declarations would be triggered almost twice as often in most regions and almost four times as often in SW of WA

The principal implication of the findings of this study is that the existing trigger for EC declarations is not appropriate under a changing climate.

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References and resources

Climate Change and Agriculture – Dept of Climate Change website.

ABARE 2007 - Australian commodities, Vol 14 no. 3 September quarter 2007 – Climate Change, pages 493-515.

CSIRO/BOM report (2008) - An assessment of the impact of climate change on the nature and frequency of exceptional climatic events.

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