Rising seas levels may benefit Waituna lagoon, Ngāi Tahu elder says

Thursday, 5 December 2019

Diggers working on a trench to open the Waituna Lagoon to the sea at Walkers Bay.

Climate change may mean that an internationally recognised lagoon in Southland may no longer need to be mechanically opened in the future.

Ngāi Tahu kaumātua Sir Tipene O'Regan delivered a presentation on the Waituna lagoon and plans for the Mahinga Kai Park at Hui-ā-Iwi recently held in Invercargill.

Contractors digging a channel to allow the Waituna Lagoon to drain into the sea. A Ngāi Tahu kaumātua believes this may no longer be needed in the future due to rising sea levels.

The site will include a 405 hectare area for Māori to practice traditional food gathering practices, as protected under a 1998 Ngāi Tahu settlement.

During the presentation, O'Regan said because of climate change, sea level rise at the lagoon would re-enter the sea on a permanent tidal basis that would greatly enrich its food capacity.

Sir Tipene O'Regan during Ngāi Tahu's Hui-ā-Iwi presentation on Waituna Lagoon. O'Regan said rising sea levels would be beneficial to food gathering at the lagoon.

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Ngāi Tahu had been collaborating with Environment Southland, Department of Conservation, Southland District Council, Te Runanga O' Awarua and Ministry of Environment into conservation efforts at the lagoon.

Te Runanga O'Awarua representative Gail Thompson said what Sir O'Regan was referring to was the current process of the lagoon having to be mechanically opened.

As the sea level rises it would create a change to the coastal area and mechanically opening the lagoon would not be a problem anymore, Thompson said.

Environment Southland general manager of operations Jonathan Streat said the estuary had been mechanically opened since the turn of last centaury.

Environment Southland freshwater and marine science team leader Nick Ward said there was the potential for the lagoon to no longer to be opened mechanically because of rising sea levels.

However other effects of climate change such an increase in the number of storms could also prevent this from happening, Ward said.

When the lagoon was opened it would naturally close because of the drift of sediment.

How climate change would effect that drift of sediment would also effect if the lagoon could naturally stay open, he said.

In terms of food production, a permanent opening of the lagoon would allow for more to species enter the lagoon, he said.

The concentration of salt in the lagoon varies as the estuary opens and closes and some species have specifically adapted to the constant change, he said.

It would be unknown how these species would further adapt to a permanent opening if it occurred, he said.

The lagoon was last opened on October 13.

Waituna Lagoon was New Zealand's first wetland to be recognised to be of international significance.