Managing climate variability in grazing enterprises: A case study for Dalrymple shire, north-eastern Australia

Abstract

In this paper we examine approaches to managing climate variability in the Dalrymple Shire of north-east Queensland. We use the forage-animal production model GRASP to evaluate the production and resource implications of grazing management and seasonal climate forecasting strategies. In this study, five forecasting strategies were assessed at each of nine test rainfall stations in Dalrymple Shire. Forecasting strategies used were: (a) spring SOI, (b) spring SOI phases, (c) an SOI phase system “tuned” to Charters Towers rainfall, (d) winter Pacific Ocean sea surface temperatures (EOF analyses), and (e) winter Pacific and Indian Ocean sea surface temperatures (EOF analyses). Stocking rates were adjusted annually according to analogue year types provided by the forecasts. In forecast “dry” years stock numbers were reduced by 50% and in “wet” years they were increased by 30%. Stocking rate changes were made in either November, when all forecasts were available, or in June, which assumes some improvement in forecasting lead time, particularly for the SOI.

Results from these analyses show that:

- seasonal climate forecasting provides more benefit to animal production when the forecasting information is available in June rather than November

- the relative value of forecasting is greater for constant grazing strategies than for flexible ones

- increased animal production derived from applying a forecast is not at the expense of the resource base and if increased animal production is not the desired aim of the forecast then significant reductions in soil loss can be achieved

- using localised forecasts does not provide any extra skill in production simulations.

Despite the demonstrated benefits of using a forecasting strategy based on the SOI, there is considerable reluctance amongst producers to adopt such forecasts. A producer survey indicated that even if more reliable forecasts were developed, most would wait until extreme events had an impact on their enterprise before making critical stocking decisions. A grazing trial has been established that will compare grazing management strategies, including a seasonal forecasting strategy, which should assist in demonstrating the potential benefits of seasonal forecasting. Even in the absence of seasonal forecasts, grazing management in the rangelands of Australia could be vastly improved through better incorporating existing understanding of climate variability into stocking decisions. In this paper we show that further value maybe added through the application of seasonal forecasting but that perhaps this added sophistication should only be contemplated after basic grazing management principles are incorporated into whole property planning.