Risk Management and Temperature

Introduction

This section explores the characteristics of temperature and associated risks and opportunities to primary production.

Agriculture, water resources and temperature

Extreme temperature events (either heat or cold) can have a large impact upon many agriculture practices. For instance, extreme heat has the potential for significantly increased mortality in poultry, pigs and even feedlot cattle. Similarly both milk production and cattle reproduction can decrease markedly during extended heat waves. Heat waves are also of major concern for fire management.

In the longer term, above average seasonal temperatures can exacerbate drought during rainfall deficiencies due to higher evaporation and increased water use uptake by plants. Yields for crops such as wheat, rice, canola, potatoes some fruits and soybeans can be reduced by high temperatures at key development stages.

Furthermore, a rise in river and estuary temperature during heat waves may impact fish populations. It may also lead to the degradation of water quality and the death of some parts of the water ecosystem. High temperatures and low water flows contribute to algal growth, which can cause fish kills in rivers and lakes.

At the other extreme, cold temperature impacts vary from location to location and commodity to commodity. Frost, and more particularly the freezing and rupturing of a plant cell walls, can damage many crops, particularly early or late in growing seasons. Prolonged cold snaps can also lead to stock losses.

Temperature information relevant to agricultural decisions

The following table lists farming decisions related to temperature, with a brief description of why temperature information is relevant and the type of information which can be used.

Decision	Why climate & weather information are important	Climate & weather information sources
Seasonal planning	Warmer weather conditions may cause crops to mature early. Or, excessive warmth and dryness may inhibit development.	Seasonal climate outlook.
Variety of crop to plant	Many crop species have a number of varieties available to help accommodate varying lengths of growing season, timing of frosts, etc.	Seasonal climate outlook.
Planting dates	Germination of seeds is temperature dependent, so there may be a balance required between optimum temperature and rainfall.	Weather forecasts of temperature and rainfall.
Depth of sowing seed	Extremely high temperatures near the soil surface could result in roasting of the seed or burning of emerging seedlings.	Weather forecasts.
Controlled burning off	Temperature, wind and humidity are extremely important in choosing safe burning days.	Weather forecasts of temperature, wind, humidity and rain.
Site selection	Particularly in horticulture and viticulture, climate records can help determine if the area is suitable for particular crops.	Climate records, including seasonal patterns of temperature and sunshine.
Horticultural and viticultural crop varieties	Low temperatures, high temperatures or frosts can be critical for certain varieties.	Climate records, including possible dates of first and last frosts of the season.
Fruit types and cultivars and orchard layout	Severe frost can affect flowering, whereas an amount of winter chilling hours is needed for some fruit types to set fruit.	Localised climate records of temperature, frosts and winds.
Disease control	For example, warm temperatures combined with high humidity is conducive to fungal disease.	Weather forecasts.
Water for stock	Hot dry weather increases stock water intake and increases evaporation from stored water.	Seasonal climate outlook, weather forecasts.
Crop spraying	Temperatures above about 30°C result in significant loss of volatile chemicals through evaporation.	Weather forecasts of temperature, wind and humidity.
Maintaining fire breaks	Temperature is one of the important factors in fire season risk.	Seasonal climate outlook.
Sheep shearing and lamb wind chill	Cold outbreaks are a problem for both.	Weather forecasts of temperature.
Insurance requirements	Extreme cold outbreaks, frosts or extreme heat waves can severely damage some crops.	Climate records of temperature and frosts.
Heat stress management for poultry, dairy, pigs	Reduced productivity and even mortality can result from heat stress. Example: Thermal stress in dairy cattle	Weather forecasts.

Much of the information in the above table is sourced from a similar table prepared by Damien O'Sullivan (QDPI) and Harpal Mavi (NSW Ag)

While less attention is sometimes paid to the risks associated with temperature when compared to rainfall, particularly at seasonal timescales, the above information shows that temperature is important in general on-farm risk management.

Seasonal forecasts for frost are currently some years away. This is primarily due to the small scales on which frost events can occur. For instance, frost may be more common in local hollows or depressions, and hence be far below the scales on which climate models make their forecasts. However general climate conditions can give a clue to the possibility of frost in areas that are susceptible. For instance, during an El Niño year, dry soils (which can hold less heat than wet soils) and the tendency for high pressure systems to dominate the continent (and hence give clear nights, with a high loss of heat), mean a greater tendency for frosts in some areas, particularly early in the local frost seasons. Keeping an eye on the Bureau's ENSO Wrap Up can give some indication of the likelihood of an El Niño event.

For short term events, local and recent conditions can make a big difference to whether frost may occur or not. The Bureau issues frost warnings or advisories in their district forecasts in all states. These should be the first port of call when there are concerns about frost risk. To get a heads-up a couple of days in advance, try using the Bureau's new frost potential service, currently being trialed on the Water and the Land website. This product lists the Bureau's automatic weather stations which the computer models suggest may have a chance of frost in the coming 48 hours. By watching these, and learning how your local station relates to conditions on your farm, you'll soon develop an appreciation for the chance of frost where it matters to you.

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