Articles | Volume 7, issue 5
Geosci. Model Dev., 7, 2359–2391, 2014
Geosci. Model Dev., 7, 2359–2391, 2014

Development and technical paper 16 Oct 2014

Development and technical paper | 16 Oct 2014

Grassland production under global change scenarios for New Zealand pastoral agriculture

E. D. Keller1, W. T. Baisden1, L. Timar1,2, B. Mullan3, and A. Clark3,* E. D. Keller et al.
  • 1GNS Science, Lower Hutt, New Zealand
  • 2Motu Economic and Public Policy Research, Wellington, New Zealand
  • 3NIWA, Wellington, New Zealand
  • *now at: New South Wales Department of Primary Industries, Orange, NSW, Australia

Abstract. We adapt and integrate the Biome-BGC and Land Use in Rural New Zealand models to simulate pastoral agriculture and to make land-use change, intensification of agricultural activity and climate change scenario projections of New Zealand's pasture production at time slices centred on 2020, 2050 and 2100, with comparison to a present-day baseline. Biome-BGC model parameters are optimised for pasture production in both dairy and sheep/beef farm systems, representing a new application of the Biome-BGC model. Results show up to a 10% increase in New Zealand's national pasture production in 2020 under intensification and a 1–2% increase by 2050 from economic factors driving land-use change. Climate change scenarios using statistically downscaled global climate models (GCMs) from the IPCC Fourth Assessment Report also show national increases of 1–2% in 2050, with significant regional variations. Projected out to 2100, however, these scenarios are more sensitive to the type of pasture system and the severity of warming: dairy systems show an increase in production of 4% under mild change but a decline of 1% under a more extreme case, whereas sheep/beef production declines in both cases by 3 and 13%, respectively. Our results suggest that high-fertility systems such as dairying could be more resilient under future change, with dairy production increasing or only slightly declining in all of our scenarios. These are the first national-scale estimates using a model to evaluate the joint effects of climate change, CO2 fertilisation and N-cycle feedbacks on New Zealand's unique pastoral production systems that dominate the nation's agriculture and economy. Model results emphasise that CO2 fertilisation and N-cycle feedback effects are responsible for meaningful differences in agricultural systems. More broadly, we demonstrate that our model output enables analysis of decoupled land-use change scenarios: the Biome-BGC data products at a national or regional level can be re-sampled quickly and cost-effectively for specific land-use change scenarios and future projections.