Despite New Zealand’s continuing development, agriculture remains a major sector of the economy, and the vast majority of farm and food production is exported. The accelerating intensification of farming in New Zealand over recent decades raises concern over the current sustainability of New Zealand farming, and whether it can remain so in the future. Livestock’s impact on the environment, especially water availability and pollution and GHG emissions, is an important domestic policy issue in New Zealand given its high share of economy-wide emissions. It has also become a trade policy issue with the growing trend for foreign buyers and policy makers to place emphasis on ‘green’ and environmentally-friendly livestock production. Therefore there is an imperative for New Zealand to work towards sustainable exportoriented agricultural production. The paper compares official GHG emissions data for New Zealand with those in the GTAP database and notes some major discrepancies. We next explain why we do not use the GTAP AEZ data for New Zealand, but instead adopt a New Zealand-specific system of land environment classification. From these data, we derive values to substitute for the GTAP AEZ data. We modify the standard GTAP model to incorporate several land classes, and run two illustrative simulations. Further research plans are presented.