A mechanistic model was used to measure the impact of changes in climate (temperature, rainfall and solar radiation) and a 75% increase in the concentration of atmospheric carbon dioxide on pasture and animal production on eight representative New Zealand lowland farming systems. The climate changes increased annual pasture dry matter production per hectare by 10-30%, assuming no changes in pasture composition. A 75% increase in CO2 concentration increased pasture production by around 40%. Together, climate change and increased CO2 concentration increased yields by 50-77%. In all cases, the seasonal distribution of pasture production was not greatly affected. Both climate change and increased CO2 concentration individually increased annual milk production per hectare by around 24%, lamb meat and beef by around 30% and wool by around 22%, under the constant farm management systems selected. The increases in production were mainly due to increases in stocking rate resulting from the increased pasture production, but increased conservation and feeding out of hay were required. The model predicted an increase in lamb growth rates. Milk, meat and wool production was higher under climate change than under increased CO2 concentration in Southland, but the opposite was true in northern New Zealand. The combined effect of climate change and increased CO2 concentration was greater, with potential increases over the two scenarios averaging 52% for milk, 57% for lamb and beef and 46% for wool.
Proceedings of the New Zealand Society of Animal Production, Volume 50, , 479-482, 1990
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