Waituna Lagoon under a changing climate: what a 2019 assessment projected
In 2019 two scientists assessed how climate change could affect Waituna Lagoon, a freshwater lagoon behind a gravel barrier in Southland, New Zealand. The IPCC’s 2022 Australasia chapter cites their assessment.
What the study did and found
The report is “Impacts and implications of climate change on Waituna Lagoon, Southland”, number 335 in the Department of Conservation’s Science for Conservation series (Tait & Pearce, 2019). Andrew Tait and Petra Pearce combined existing climate, river-flow and sea-level projections with a LiDAR elevation model.
Under high emissions they projected mean annual inflow more than 50% higher by the end of the century, and, while the lagoon is open to the sea, 64% less intertidal mudflat with 1 m of sea-level rise (Tait & Pearce, 2019). They concluded that openings would need to come more often and would likely get harder as the sea rises.
Why it is cited
The referring page is Chapter 11 (Australasia) of the IPCC’s 2022 Working Group II report, which lists the record as a bare Cabdirect link and cites the study for the statement that sea-level rise “will shrink the intertidal zone” (Lawrence et al., 2022).
The use fits the report’s main mapping result but drops its caveats: Tait and Pearce called the shrinkage likely, for one lagoon only while open to the sea, whereas the IPCC states it generally.
The assessment added no field data, and its mapping assumes a fixed tidal range, a barrier that survives to 2100 and no vertical land movement; one entry in its area table is internally inconsistent (Tait & Pearce, 2019).
Later work supports the report’s sea-level timing under higher emissions (Ministry for the Environment, 2024), and monitoring since 2019 fits its concern that openings harm Ruppia (de Winton et al., 2025), but its inflow figures remain untested against newer projections.
The topic today
In October 2025 independent commissioners approved a 20-year opening consent, with triggers reported to rise from 2.3 m to 2.5 m (Southland Tribune, 2025). Federated Farmers appealed, and mediation was scheduled for July 2026 (Southland Conservation Board, 2026).
For the current picture, see our explainer Waituna Lagoon and Sea-Level Rise: What the 2019 Study Found.