Role of climate and rainfall in grazing systems
Climate plays a major role in forming the characteristics of a land type and the pasture that grows there.
Queensland is a large state with a diverse climate, ranging from tropical and wet in the north to subtropical in the south. In the arid inland regions, conditions can be extremely hot or cold depending on the time of year. Climate can also vary widely within and between years.
Queensland has over 230 types of grazing land so there is no easy formula for pasture management. Rain, heat, humidity, wind and frost all affect pasture composition, quantity and quality.
Rainfall and grazing systems
Annual rainfall in Queensland varies greatly between regions—from 2000-4000mm on the tropical coast to 150-250mm in the south-west. In the north, most rain falls in summer, while south of the Tropic of Capricorn, winter rain is an important part of the annual total, rising to about 40% along the southern border.
Annual rainfall averages
Rainfall information is valuable, but it can be misleading. Annual rainfall averages imply what is 'normal' and what can be expected for pasture growth. However, averages can be skewed by very high rainfall recordings and extreme weather events.
Total rainfall figures
Total rainfall figures may also be misleading because intense rain may have occurred over a few days rather than in steady rain events across a season. Intense rain usually runs off the soil instead of being absorbed, so it is less effective for pasture growth than steady gentle rain. During wet times, pasture may grow quickly and become dense, but have low protein content.
Rainfall and pasture growth
The effectiveness of rainfall in leading to pasture growth is determined by:
- ground cover (pasture condition and species)
- soil type and condition
- rainfall intensity
- tree cover.
Predicting rainfall in Queensland
While predicting weather is an inaccurate science, the Rainman StreamFlow software can help to calculate the chances of monthly and seasonal rain in a regional area. This CD-based software package contains historical rainfall data for 3700 Australian locations.
Temperature and grazing systems
Consider local temperature averages and extremes as part of your pasture management plan or when selecting improved pasture species, as temperatures can affect pasture growth.
For example, find out if your local area often experiences:
- temperatures over 32 degrees Celsius, and heatwaves
- temperatures below freezing, and frosts.
The interaction of temperature, rainfall and sunlight has a direct effect on pasture growth. Pastures grow well during warmer months provided there is enough moisture. In winter, growth is minimal; however, forbs can be abundant, providing extra pasture quantity and protein for grazing livestock.
Climate change and grazing systems
Future impacts of climate change, while uncertain, may make the job of managing grazing lands even more complex. There may be more intensive rainfall events but reduced overall rainfall figures. Predicted rises in temperature and associated evaporation rates may cause stress to animals, pasture production and land health. However, there may also be some benefits.
Effects of climate change that may benefit your grazing system
The potential benefits from climate change to grazing and pasture management include:
- more pasture growth in spring and winter
- less frosts
- less stress on animals in winter
- different responses by pasture species, which may lead to changes in pasture composition.
Effects of climate change that may damage your grazing system
The potential damage from climate change to grazing and pasture management include:
- higher rainfall intensity
- more potential evaporation
- more soil evaporation
- less pasture growth in summer and less digestibility
- trees dying during droughts
- more animal heat stress in summer
- less grazing time and greater water demands
- more diseases and pests in hot and wet conditions
- increased stress on human health (including heat stress).
How to manage your property due to effects of climate changes
To make sure your property continues to operate successfully, despite climate change, you should:
- research climate information and predictions for future weather conditions
- review your property's carrying capacities to make sure it is safe
- review your grazing management options (e.g. grazing system, distance to water)
- explore animal husbandry options (e.g. joining, calving times)
- choose livestock types and breeds best suited to the conditions.
Note: effects of climate change information from Hamilton J, Paton C, Chilcott C, and Quirk M, 2009, Grazing Land Management education package workshop notes – Border Rivers, Meat and Livestock Australia, Sydney.