Climate change impacts and adaptation: a New Zealand dairy system : A thesis submitted in partial fulfilment of the requirements for the Degree of Master at Lincoln University

Abstract

Pasture-based farming systems, as in New Zealand, are susceptible to changes in the climate through feed supply variability. Future climate change will likely alter pasture growth patterns, posing opportunities and risks that farmers will have to respond to and adapt to remain profitable. Due to the heterogeneous nature of farm systems in New Zealand, adaptation strategies must be evaluated on a farm-by-farm basis. The main objectives of this research were to use a case-study methodology to evaluate the impacts of climate change on a dairy farm system, and to investigate a range of farm management strategies aimed to maintain productivity and profitability. The study was based on the Northland Agricultural Research Farm (NARF; 35⁰56’39” S 173⁰50’34”E), using performance and farm management data over three production seasons to set up a baseline farm. Whole farm systems modelling was used to simulate climate change effects on the baseline farm in the middle and end of the 21st century. Two dynamically downscaled climate change scenarios for the baseline farm were provided by the National Institute of Water and Atmospheric Research (NIWA). These were used in the mechanistic model, DairyMod, to simulate the effects of climate change on the pasture growth rates of the baseline farm in the middle and end of the century under two warming pathways. These growth rates were used in the whole-farm systems model, Farmax, to simulate the feasibility of the farm in the middle and end of the century with altered pasture supply as impacted by climate change projections. Tactical system changes were used to match the herd’s energy demand with the altered pasture supply curves in order to re-optimise the farm system impacted by climate change. The findings of this research identified that with the use of systems changes, farms in the Northland region of New Zealand may reduce negative impacts on production and profit associated with climate change. A second round of modelling work was completed using the strategic adaptation strategy of utilising alternative pasture species that may be better suited to the changing climate. Differences in the morphological and physiological characteristics of the baseline and adapted pasture resulted in different pasture supply curves impacted by climate change. These required more extreme system changes compared with the baseline pasture. However, with the use of system changes, production and profitability were maintained or increased compared with the baseline farm. Overall, this study showed that with the use of farm system changes farmers may be able to capitalise on the opportunities associated with climate change to offset the risks.