Improved pasture management can improve profitability and resilience to climate change in northern Australia

Abstract

A Northern Grazing Systems (NGS) project is identifying and promoting key management practices to help improve the profitability and sustainability of the extensive beef industry of northern Australia. The project's initial focus was management practices that perform best under current climate, but now the emphasis has turned to exploring the role these practices may play in helping beef producers adapt to changing climate. This paper reports the preliminary results of using a bio-economic modelling (BEM) framework to compare the performance of a range of pasture management practices under current climate and two projections of future climate. The BEM framework used was linked variants of the GRASP pasture growth model and the ENTERPRISE beef herd economic model. The main metric used to compare management practices was average annual profit. Management practices were compared on a representative beef grazing property located near the township of Mitchell, in southwestern Queensland. It has around 1,400 breeders on 17,000 ha of native and improved pasture, and sells weaner steers, surplus heifers and cull breeding cows at local sale yards. A flexible stocking rate practice, allowing up to 20% increases and 40% decreases in stocking rate over 25 years in response to variability in annual forage availability, was compared with fixed stocking rates. A wet season pasture rest for six months once every four years was compared with continuous grazing, and a prescribed fire scheduled to occur every four years was compared with no burning. These management practices were simulated over the last 25 years (1986 to 2010) of current climate at Mitchell, and two projections of climate change. Projections of climate change, representing the range of possible changes in climate, were: 1) a ~3°C increase in minimum and maximum temperatures and a marginal (1%) decrease in rainfall; and 2) a ~3°C increase in temperatures combined with a 27% reduction in rainfall. The flexible stocking rate practice performed better than fixed stocking rate under current climate. While fixed stocking was sustainable and profitable, in current climate, flexible stocking was able to improve and maintain pasture condition, enabling carrying capacity, annual stocking rates and livestock productivity to increase. Under projected climate change, the modelled carrying capacity of the representative beef property was lower, especially under Projected Climate 2. Fixed stocking rates that were appropriate under current climate were too high under the two projections of climate change. Pasture condition and livestock productivity declined markedly, leading to low or negative average annual profit. The flexible stocking rate practice was able to match stocking rates to declining feed availability and carrying capacity, and therefore adapt the property to Projected Climate 1. However, it was not responsive enough to match stocking rates with the more severe reductions in carrying capacity that occurred with Projected Climate 2. Annual stocking rates were too high, resulting in poor pasture condition and low livestock productivity. Under current climate, wet season pasture resting enabled pasture condition to improve, leading to increases in carrying capacity, annual stocking rates, livestock productivity and profit, compared with continuous grazing. Prescribed fire, compared to no burning, prevented increases in woody regrowth that reduced carrying capacity, and was better able to maintain pasture and livestock productivity. Pasture resting and prescribed fire were partially successful in mitigating the impacts associated with the lower carrying capacity of Projected Climate 1, but were ineffective under Projected Climate 2 with its even lower carrying capacities where high stocking rates were the dominant influence on biological and economic relationships.