Sustainable management for rangelands in a variable climate: evidence and insights from northern Australia

Abstract

Inter-annual rainfall variability is a major challenge to sustainable and productive grazing management on rangelands. In Australia, rainfall variability is particularly pronounced and failure to manage appropriately leads to major economic loss and environmental degradation. Recommended strategies to manage sustainably include stocking at long-term carrying capacity (LTCC) or varying stock numbers with forage availability. These strategies are conceptually simple but difficult to implement, given the scale and spatial heterogeneity of grazing properties and the uncertainty of the climate. This paper presents learnings and insights from northern Australia gained from research and modelling on managing for rainfall variability. A method to objectively estimate LTCC in large, heterogeneous paddocks is discussed, and guidelines and tools to tactically adjust stocking rates are presented. The possible use of seasonal climate forecasts (SCF) in management is also considered. Results from a 13-year grazing trial in Queensland show that constant stocking at LTCC was far more profitable and largely maintained land condition compared with heavy stocking (HSR). Variable stocking (VAR) with or without the use of SCF was marginally more profitable, but income variability was greater and land condition poorer than constant stocking at LTCC. Two commercial scale trials in the Northern Territory with breeder cows highlighted the practical difficulties of variable stocking and provided evidence that heavier pasture utilisation rates depress reproductive performance. Simulation modelling across a range of regions in northern Australia also showed a decline in resource condition and profitability under heavy stocking rates. Modelling further suggested that the relative value of variable v. constant stocking depends on stocking rate and land condition. Importantly, variable stocking may possibly allow slightly higher stocking rates without pasture degradation. Enterprise-level simulations run for breeder herds nevertheless show that poor economic performance can occur under constant stocking and even under variable stocking in some circumstances. Modelling and research results both suggest that a form of constrained flexible stocking should be applied to manage for climate variability. Active adaptive management and research will be required as future climate changes make managing for rainfall variability increasingly challenging.Keywords: grazing strategies, profitability, land condition, climate forecasts, simulation models ImplicationsEvidence from northern Australia suggests that managers should apply a form of constrained flexible stocking with upper limits to stocking rate of about 20% to 40% above long-term carrying capacity. Stocking rates should be tactically adjusted on the basis of forage availability, and where appropriate, informed by seasonal climate forecasts. Even in the best years, annual stocking rate increases should be limited to 10% to 20% in order to avoid overstocking in the event of poor subsequent seasons....

Bodyweight performance, estimated carcass traits and methane emissions of beef-cattle categories grazing Andropogon gayanus, Melinis minutiflora and Stylosanthes capitata mixed swards and Brachiaria humidicola pasture

“…Thus, long-term grazing experiments are essential in providing a firm basis for recommendations regarding the management of properties and resources (Blench 2001;O'Reagain and Scanlan 2013;Scanlan et al 2013); and for adequately matching animal genotype and its expressed phenotype to those production resources, particularly as costs of production and competition for land resources increase (Mulliniks et al 2015).…”

The impact of cattle grazing regimes on tropical savanna bird assemblages

“…The 1040 hectare trial was established to test the long‐term economic sustainability of several cattle grazing strategies (O'Reagain et al . , ; O'Reagain & Scanlan ). This area has a distinct summer wet season and winter dry season, typical of tropical savanna.…”

Large‐scale and local climatic controls on large herbivore productivity: implications for adaptive rangeland management

“…). Such problems stem from poor recognition of temporal variability in precipitation, its predictability, and oversight to manage accordingly (O'Reagain and Scanlan ). To date, research efforts have primarily addressed relationships between precipitation and forage production (Le Houérou and Hoste , Milchunas et al.…”

“…In Australia, more robust atmospheric teleconnections between rainfall and the Southern Oscillation Index (SOI) provide forecasting tools with considerable promise in assisting managers with herbivore density adjustments further in advance (several months) of the next growing season (Ash et al. , O'Reagain and Scanlan ). Collectively, these observations suggest uncertainty in mass gain outcomes for variable large herbivore densities can be reduced by integrating prevailing large‐scale climate modes as well as local‐scale precipitation amounts into current grazing‐season planning.…”

“…One-and threemonth precipitation forecast maps (NOAA 2019) and GrassCast ; available online) 5 are tools available to assist decision-making for livestock producers in North America, but these forecasts still have high uncertainty prior to the start of the growing-season (e.g., in April). In Australia, more robust atmospheric teleconnections between rainfall and the Southern Oscillation Index (SOI) provide forecasting tools with considerable promise in assisting managers with herbivore density adjustments further in advance (several months) of the next growing season (Ash et al 2002, O'Reagain andScanlan 2013). Collectively, these observations suggest uncertainty in mass gain outcomes for variable large herbivore densities can be reduced by integrating prevailing large-scale climate modes as well as local-scale precipitation amounts into current grazing-season planning.…”