From mountains to the sea: values and science for an informed kaitiaki/guardian - land

This version of the report (January 2025) has all corrections in the text and tables integrated. The previous version included a separate corrigendum (6 December 2024)

This project aimed to assess the impacts and implications of meeting contaminant reduction targets for estuaries on catchment land-use and management. The objectives were to:

• Estimate the time distribution of contaminant loads at sub-annual scales.
• Estimate catchment contaminant loads to all case-study estuaries, i.e. Kaipara Harbour, New River, and Waihi, and to all New Zealand estuaries under changed climate and mitigations.
• Identify catchment land-use scenarios for a range of contaminant reduction targets for estuaries.

The project found the adoption of feasible mitigation options in combination with targeted moderate land-use change will be able to sustain a significantly improved ecological health of New Zealand estuaries and rivers. Increased effort implementing sediment mitigation measures is required to keep up with climate-driven exacerbation of sediment generation, especially in soft-rock hill country. For estuaries susceptible to eutrophication or whose catchments exceed NPS-FM bottom lines for one or more contaminants, implementing P and sediment mitigation measures alongside N mitigation measures targeting a 60% N reduction could sustain a considerably improved ecological health of estuaries and rivers.