Estimated effects of climate change on grassland production and legume content across southern Australia

Estimated effects of climate change on grassland production and legume content across southern Australia

Climate change is predicted to have a substantial negative effect on the productivity of grasslands across southern Australia (Moore & Ghahramani, this conference). We used the GRAZPLAN biophysical simulation models to assess several possible pasture, and genetic improvement adaptation options under SRES A2 scenario between 2016 and 2085. Simulations spanned five dimensions: space (25 representative locations), time, global circulation models (4 GCMs), livestock enterprise, and management (8 adaptation options). In the absence of adaptation, overall average profitability of livestock systems declined by 53%, 69%, and 86% at 2030, 2050 and 2070. Declines in profitability were greatest for locations at the dry margin of the farming zone. “Relative effectiveness” of adaptations evaluated by their recovery effect to return decline in income to a historical period of 1970-99. Increased soil fertility was the most effective adaptation option, with continent-wide relative effectiveness of 60%, 67% and 44% at 2030, 2050, and 2070. Increasing conception rates was the most effective genetic adaptation trialled (at 26% overall effectiveness) and confinement feeding in summer had an overall effectiveness of 22%. Adding Lucerne to the feedbase, removing annual legumes in an attempt to preserve ground cover and increasing livestock body size or fleece weight were less effective. At many locations (e.g., half in Merino ewe) it appears unlikely that a single adaptation can return profit to historical levels. Combinations of adaptations can be found to return most livestock systems to historical profitability or even higher at 2030 but by 2070 effectiveness of adaptations significantly decreases.

c. 2013.