Estimating Co-benefits of Agricultural Climate Policy in New Zealand: A Catchment-Level Analysis

This paper uses an economic catchment model to assess changes in land use, enterprise distribution, greenhouse gas emissions and nutrient loading levels from a series of policies that introduce carbon prices or nutrient reduction caps on land-based production in the Hurunui Catchment in Canterbury, New Zealand. At $20/tCO2e, net revenue for the catchment is reduced by 7% from baseline levels while GHGs are reduced by 3%. At $40/ tCO2e, net revenue is reduced by 15% while GHGs are reduced by 21%. Nitrogen and phosphorous loading levels within the catchment were also reduced when landowners face a carbon price, thus providing other benefits to the environment. Additional scenarios in this paper assess the impacts from developing a large-scale irrigation project within the catchment. Results show that while adding irrigation can improve farm output and revenue, it also results in dramatically higher GHG emissions and nutrient loads. Placing a carbon price on land-based activities diminishes some of these pollutants, but not at the same rate as when the policy what enacted on the baseline irrigation levels. Finally, we investigate the impacts of imposing a nutrient loading cap on farm activities instead of a carbon price and find that if landowners had greater access to irrigation but were constrained to hold the nutrient loads at baseline levels, revenue could increase by 6% over the baseline while GHG emissions could be reduced by 5%. Our findings suggest that while there is a potentially a strong trade-off between water quantity and water quality in the Hurunui Catchment, imposing the right policy levers could reduce some of the environmental impacts from an increase in land-use intensity without placing a large economic or regulatory burden on its landowners.