Modelled potential distribution of tropical pasture species in current and future climates for Australia, with a focus on south-eastern Australia

Context Climate change is increasing temperatures, affecting the water cycle and other climate variables. In south-eastern Australia, winter rainfall has declined, whereas summer rainfall has remained stable or increased slightly. Future projections indicate that these trends will continue, and the summer–early autumn feed gap in grazing systems dominated by temperate pasture species is predicted to increase. Tropical perennial species are responsive to summer rainfall and may be a suitable addition to grazing systems, although their potential distribution is not known. Aim Our aim was to model and compare the potential distribution of six tropical pasture species under a historic baseline climate (1981–2010) and 2050 (2035–2065) future climate scenarios (by using two contrasting global climate models; MIROC-H, CSIRO-Mk 3.0) for Australia, with a focus on south-eastern Australia. Methods Species distribution based on climatic suitability of Cenchrus clandestinus, Chloris gayana, Digitaria eriantha, Megathyrsus maximus, Panicum coloratum var. makarikariense and Desmanthus virgatus was modelled using CLIMEX. Outputs were restricted by soil pH and land-use suitability to form a combined model of species distribution. Key results On the basis of where these species are currently sown, they occupy only a proportion of their potential. The 2050 climate scenarios suggest that the potential distribution of these species will decrease in northern Australia. In south-eastern Australia, suitability will increase if temperatures rise with minimal change to rainfall (MIROC-H A2), but decrease if rainfall decreases significantly (CSIRO-Mk 3.0 A2). Conclusions Our study indicated that these species may be suitable in new areas, including south-eastern Australia under both current and future climate scenarios. Further field testing is required to confirm their persistence, productivity, interaction with soils, and position in the landscape. Suitability of these grasses could provide an additional feedbase strategy for adapting to a changing climate. Modelling is subject to limitations, owing to parameter assumptions, exclusion of some soil and management factors, and uncertainties inherent in climate projections; these can be addressed through integration of finer-scale environmental data and targeted field validation.