Effects of climate scenarios on simulated intake of sheep grazing native pastures in northern New South Wales, Australia

Abstract

Interpolated climate data were used as inputs for simulations in a biophysical model to predict the proportion of the total intake provided by native pasture for wethers and ewes for three climate scenarios on the North-West Slopes of New South Wales (NSW), Australia. These climate scenarios compared the 1961–90 historical baseline climate with two climate projections for 2030 based on (i) the Intergovernmental Panel on Climate Change A1B scenario in 2030 for a site near Barraba, and (ii) a report to the NSW Government indicating that the climate of Tamworth (~85 km south-east of Barraba) could become similar to that of Warialda (~95 km north-west of Barraba). A third scenario compared historical data for the Barraba location for 30-year ‘dry’ and ‘wet’ periods, in the first and second halves of the 1900s, respectively. Model simulations indicated that the largest differences in the predicted proportion of wether and ewe intake provided by the pasture occurred for the historical ‘dry’ and ‘wet’ periods. For the reference climate normal (1961–90) v. 2030 A1B scenario and the Tamworth–Warialda comparison, there were few substantial differences in the predicted proportion of pasture intake. Additionally, there was only a small effect of a variation (up to 20%) in rainfall distribution and inter-annual variability on pasture intake by sheep. Since the largest predicted differences in sheep intake of pasture occurred for historical ‘wet’ and ‘dry’ periods, it was apparent that climate variability would continue to have a major influence on grazed native pastures on the North-West Slopes of NSW.