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Summer rainfall is the dominant influence on pasture composition in Astrebla grasslands, although grazing can modify this rainfall influence. Predictions for climate change for northern Australia suggest reduced rainfall totals with increased rainfall variability.

This paper compares the frequency of four grass and four forb species on two sampling occasions in Astrebla grassland. The first sampling occurred following three years of increasing summer rainfall while the second sampling occurred following three years of declining summer rainfall. The frequency of three of the four grasses was higher following good rainfall while that of the four forb species was higher following below above rainfall.

Results indicate that, with a likely climate change scenario of reduced rainfall coupled with increased variability, that Astrebla grasslands are likely to have increased Astrebla spp. plant turnover, higher forb and lower grass species frequencies. Grazing management will need to monitor these changes in species composition to adjust carrying capacities for sustainable production.