Report shows species threatened at Waituna Lagoon by climate change

Monday, 23 December 2019

The risk of climate change to a variety of threatened plants, birds and fish living in Waituna Lagoon has been highlighted in a new report by the Department of Conservation.

The report says that climate change would pose a threat to the native seaweed ruppia, vital to the lagoons ecosystem as it holds sediment, absorbs nutrients and releases algae.

The abundance of ruppia was a determining factor in the health of the lagoon and it was sensitive to changes in water level and concentration of salt, the report says.

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It also says that changes to rainfall, that would decrease in summer and increase from autumn to spring, would reduce the habitat for fish and the availability of food for birdlife.

The average air temperature was expected to rise between 0.5 to 2.5 degrees, depending on the rate of increase of carbon emissions.

The rising temperature may increase the growth of algae in the lagoon.

Earlier this month during a Hui-ā-Iwi being held in Invercargill, Ngāi Tahu kaumatua Sir Tipene O'Regan said that climate change may benefit the lagoon by creating a constant tidal flow.

The lagoon has been mechanically opened by a digger for decades when the water level exceeded two metres above a gauge in winter and 2.2 metres in spring, summer and autumn.

However, the report suggested otherwise and that because of rising sea levels the lagoon would either have to be opened more frequently or the threshold changed for when it opens.

Minister of Conservation Eugenie Sage said the report illustrated the need to act now to manage climate change impacts.

Waituna Lagoon was important for Te Rūnanga o Awarua and a natural treasure for New Zealanders, as many wetlands were already destroyed, Sage said.

The lagoon was the first wetland New Zealand to be granted Awarua Wetland Ramsar status for its ecological importance.

Recommendations made in the report included that management plans be reviewed every 10 years and for a focus on the catchment and drainage at the lagoon.

Environment Southland land and water services manager Fiona Young said the research provided useful information for Environment Southland's work at the lagoon. 

Any actions that would be made as result of the report would be considered which would be made in the new year, given the importance of climate change, Young said.