In This Section

Climate variability

What the Climate Models are saying

While there is some variation across dairy regions, climate projections for all dairy regions suggest:

  • Temperatures are likely to increase by about 1oC by 2030 
  • Rainfall is likely to decrease by around 2-5%, and there may be changes in seasonal rainfall patterns
  • Dry days are likely to increase, as is rainfall intensity on the days it does rain
  • Run-off is likely to be reduced
  • Evaporation rates are likely to increase
  • Climate variability is likely to increase, ie more extremes of temperature and rainfall, and longer droughts. This is reflected in the graph below which shows that while there were on average 10 new high temperature records per year at Australian weather stations during the 1960s, this has gradually increased to 22 new records per year in the first decade of this century. 

 


Figure 1. Number of record high temperatures recorded at Australian weather stations – source, BOM. The line plots the annual changes while the red bars show the decadal trends.

 

There are 2 problems with the climate projections:

  • They’re based on models - which simplify complex climate/weather systems. As such, we can have more faith in the predicted trends than absolute oC change by a certain date.
  • They work on averages - yet, farming is not about averages, it’s about managing day to day, season to season climate variations.

Positive and negative effects of climate change

The overall impact of climate projections for dairy farming is difficult to evaluate – some changes will generate positive outcomes, while others will give negative results. For instance:

  • As temperatures increase, then there is likely to be more heat stress on cows (and pastures/crops) over summer, and perhaps greater contributions from the low quality sub-tropical grasses (such as paspalum and kikuyu) in pastures, but pasture growth in winter and early spring is likely to increase in response to warmer conditions
  • If temperature and rainfall changes mean that the seasonal peaks and troughs of pasture or forage production shift, then the timing of key farm activities and operations, like calving times, sowing times, forage conservation activities, feeding out strategies etc will shift, with a range of potentially negative and/or positive implications for the whole farm system
  • If rainfall declines, then there will be lower irrigation allocations and there may be a shortage of water for wash-down etc. On the other hand, there are likely to be fewer waterlogging and wet soil grazing problems
  • If atmospheric CO2 increases, there will be a positive effect on pasture/forage yield and water use efficiency although there will be a decrease in protein content. This boosting effect from higher CO2 levels is stronger for temperate species than for sub-tropical species.

How these effects play out on individual farms is difficult to predict, and makes recommendations for ‘climate change preparation’ equally difficult.

The answer is to forget about the averages associated with climate change and focus on the reality of climate variability.

Back to top

Forget about Climate Change, focus on Climate Variability

Managing climate variability (be it week to week, year to year) has always been a big part of dairy farming. Most dairy farmers agree that the climate has become more variable – and whether or not it’s been human-induced, whether its droughts, floods or record high temperatures, dairy farmers still have to manage it. 

Pasture production changes from year to year can help us understand the climate variability challenge on dairy farms. Figure 1 plots pasture yields at Ellinbank dairy research centre in Gippsland, from 1960 to 2006 – and Gippsland has one of the least variable climates of all Australian dairy areas. Over those 47 years, average pasture production has increased by 1.4t/ha, or an annual increase of 30kg/ha.

Imagine you’re a farmer in 1960, and the scientists tell you “on average, pasture growth will increase by 30kg/ha/yr for the next 50 years”. What would you do?

If you bought more cows for the extra pasture growth, you might be caught out by the fact that pasture production in the next 4 years will be 1 and 2 t/ha less than the starting average, let alone projected increases.

Clearly the challenge in getting a dairy farm profitably from 1960 to 2006 has nothing to do with the slow, long term increase in average pasture yield, and everything to do with surviving the years with low pasture growth, without compromising your ability to do well in years of high pasture growth.

It’s the same with managing the projected changes in the average climate and thus the overall conclusion – forget about climate change, and focus on managing through the variability. It is likely this variability itself will increase, making the climate variability challenge for the future, potentially even greater than it has been in the past.

Total biomass production - Ellinbank 1960-2006

Figure 2 – Yearly average pasture production at the Ellinbank dairy research centre in Gippsland. The black line is the fitted average, showing a gradual increase in pasture production over time.

Back to top

References and resources

The Managing Climate Variability Program has been helping Australian farmers to manage climate risk on-the-ground for over a decade, providing them with practical tools to incorporate climate information into farm business decisions.

Back to top