Private land-use decisions are critical for a broad spectrum of environmental and social outcomes, ranging from water quality and climate change to rural income distribution. I use a large dataset of the land-use decisions of New Zealand landowners to estimate a cross-sectional multinomial logit model of land use. In this model, the optimal land-use choice depends on geophysical attributes of the land, the cost of access to markets, and on land tenure (M?ori freehold title versus general freehold title). I employ the estimated relationship in a counterfactual scenario to assess the overall impact of M?ori tenure on the willingness of landowners to supply land for the four most important rural uses in the country: dairying; sheep or beef farming; plantation forestry; and an economically unproductive use, scrub. This allows me to conjecture about the environmental implications of New Zealand’s land-tenure system.

This research has been funded by the Ministry of Science and Innovation through the "Integrated Economics of Climate Change", "Markets and Water Quality" and "Sustainable Land Management Mitigation and Adaptation to Climate Change" programmes. I thank Suzi Kerr, Dave Maré, Troy Baisden and Tanira Kingi, as well as audiences at Te Puni Kōkiri and the Ministry for the Environment, for useful comments. Thanks are also extended to Wei Zhang for his assistance in constructing the land-use dataset. I am, of course, solely responsible for any errors.

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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 nationalscale estimates using a model to evaluate the joint effects of climate change, CO 2 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 CO 2 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.