Medium-term impacts of grassland and forestry integration on the environmental performance of a New Zealand pastoral system

At the IGC in 2008, we presented a paper outlining a project that aimed to improve the economic and environmental performance of a New Zealand hill country pastoral catchment farm system. This project was undertaken by engaging a wide group of sector stakeholders in visioning, modelling, planning and implementing significant land use change within a 296-hectare pastoral farm. In recognition of developing sectoral views of agricultural sustainability, the major changes involved pine afforestation, livestock production intensification, protection of waterways and indigenous bush restoration. The report in 2008 outlined the positive impacts on key farm systems and water quality performance indicators after 4 years. Additional data on these and other parameters have been collected in the subsequent 20+ years. Some indicators have not followed expectations in afforested sub-catchments, nitrate-N concentrations in drainage waters have steadily increased and no significant decreases in annual suspended sediment loads have been detected. Other indicators have changed as expected with the exclusion of livestock access to riparian areas, indigenous bush understory has regenerated and stream ammonium-N concentration spikes have decreased; and stream water temperatures have decreased with headwater afforestation. Improvements in animal productivity have reduced emissions intensity from 25 to 15 kg CO_2-e per kg product. Afforestation and associated carbon sequestration have more than offset livestock and soil emissions to move the system from a net CO₂ source to a projected net CO₂ sink for the next 100+ years.