Climate change risks to lagoon identified
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 lagoon’s 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.
It also says that changes to rainfall, which 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 Celsius, 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-a¯-Iwi being held in Invercargill, Nga¯ i Tahu kaumatua Sir Tipene O’Regan said that climate change may benefit the lagoon by creating a constant tidal flow.
For decades, the lagoon has been mechanically opened by a digger 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 Ru¯ nanga o Awarua and a natural treasure for New Zealanders, as many wetlands were already destroyed, Sage said.
The lagoon was the first New Zealand wetland 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 necessary action resulting from the report could be taken in the new year, given the importance of climate change, Young said.