Lake Taupō Nitrogen Cap-and-Trade — Waikato Regional Council's Water-Quality Trading Scheme

Lake Taupō, New Zealand's largest lake, was losing its exceptional water clarity as nitrogen leaching from pastoral farms and forestry conversion built up in the catchment's groundwater; after over a decade of technical investigation, consultation and Environment Court hearings, Waikato Regional Council adopted Regional Plan Variation 5 in 2011, creating what researchers describe as the world's first cap-and-trade scheme for a diffuse agricultural pollutant.

Cap catchment-wide nitrogen loss and let farmers trade, lease or permanently sell tradeable Nitrogen Discharge Allowances, achieving a 20% cut in nitrogen reaching the lake at lower cost than a uniform regulatory cap.

Individual farmers received tradeable allowances benchmarked on 2001–2005 land use; the public Lake Taupō Protection Trust, funded by an NZ$81.5 million fund (two-thirds central government, one-third regional/district councils), bought out and permanently retired nitrogen rights, purchased land for retirement from farming, and supported 27 long-term (999-year) land-use-change agreements.

By 2012, roughly 90% of catchment farmland had been benchmarked and allocated allowances; the Trust's purchases and land-use-change agreements secured a reduction of about 170 tonnes of manageable nitrogen a year, meeting the scheme's 20% target. Nitrogen-right purchases are now complete and the programme has moved into a long-term monitoring phase.

Independent Motu Economic and Public Policy Research evaluations find the scheme met its ecological target at lower cost than a uniform regulatory cap would have achieved, since trading let reductions happen where land-use change was cheapest — but market trading activity itself has been limited beyond the initial buyout period, and Māori landowners' historic land claims complicated the initial allocation of allowances.