Modeling the Effects of Climate Variability and Climate Change on a Pastoral Farming System

A simulation model was used to investigate the pasture and animal production and gross margins of a typical all sheep permanent pasture farm in South Canterbury, New Zealand, using 60 years of current climate data, and also a climate change scenario. The model was run on a fixed management system at different stocking rates with and without destocking during feed shortages. Mean annual pasture production was 8060 kg/ha, with a coefficient of variation of 22%. Destocking enabled more stock to be carried on average, with higher, but rh.ore variable, returns. A climate change scenario of a 75% increase in CO2' 1.8°C rise in mean temperature, a 5% decrease in rainfall and an 8% increase in solar radiation produced 46% higher but more variable pasture yields, resulting in optimum stocking rates, costs1 returns and gross margins all being increased 25-50%.