The effect of climate change on a New Zealand dairy system

Abstract

Temperate pasture-based farming systems are vulnerable to changes in the climate. In New Zealand, there is growing farmer interest in climate change adaptation strategies that will minimise production or profit losses over the coming decades. The objectives of this study were to quantify the effects of two future climate scenarios on the performance of a modelled dairy farm in the Northland region of New Zealand at the middle and end of the century, and to evaluate the impact of adaptation strategies on farm profit. The current farm (‘baseline’) relies on kikuyu (Cenchrus clandestinus (Holst. Ex Chiov.)) and Italian ryegrass (Lolium multiflorum Lam.) to maintain year-round pasture production. Mid- and high-emission climate scenarios were sourced from the National Institute of Water and Atmospheric Research (NIWA) to simulate the potential effects of climate change on pasture supply. Future pasture supply and farm profitability were simulated using the mechanistic model DairyMod and commercial Farmax model, respectively. Overall, annual pasture yield increased in all future scenarios compared with the baseline, however, pasture growth patterns were altered. The changes in pasture growth patterns were less severe in the mid-emission than high-emission scenarios, with the end of the century scenario producing 7% more pasture DM than the baseline. In comparison with the baseline, pasture growth increased (11% and 22%) from winter to mid spring, but reduced in December (30% and 40%) for the high-emission scenario in the middle and end of the century, respectively. The modelled adaptation strategies demonstrated the potential to increase farm profit in all future scenarios compared with the baseline, with the end of the century mid-emission scenario increasing profit by 11%. This suggests that minimal adverse effects are expected from future climate change on the performance of kikuyu-Italian ryegrass-based dairy systems in the Northland region of New Zealand, and that farm profit may be improved by tactically managing changes in feed supply and animal demand. However, the methods applied do not take extreme weather events into account, and implications of these should be investigated in future work.