Restoring Aotearoa New Zealand’s Seagrass Meadows

The three-year project will develop a blueprint for seed-based seagrass restoration that can be carried out across Aotearoa. The aim is to enable large-scale restoration of seagrass meadows, helping to support biodiversity, improve water quality and sequester carbon.

This blueprint approach will be trialled in a Nelson Haven case study before the findings are used to produce information and resources that could inform scalable seagrass restoration projects throughout Aotearoa.

Although the preliminary approach will trial seed-based restoration techniques, the Project might end up trying other approaches like seagrass nurseries or planting fragments.

Restoration projects around the world have achieved success by directly sowing seed into the wild and Cawthron researchers plan to trial a similar approach with the aim of identifying the most effective method for New Zealand’s unique environment.

Funders: Westpac NZ Government Innovation Fund, OneFortyOne Limited, Port Nelson, Friends of Nelson Haven and Tasman Bay, the University of Waikato and the Catalyst Fund.

Previous funding: Nelson City Council, Ngā Pae o te Māramatanga and Cawthron Institute Trust Board.

Background

Seagrass is more like a plant you’d find on land than it is like seaweed, with long green leaves and a root structure it uses to spread. It grows in coastal sandflats in estuaries and harbours, and further out to sea in underwater meadows. It needs lots of sunlight as it depends on photosynthesis to survive, and doesn’t do well in turbid (murky) water. 

Seagrass meadows support ecosystem health in coastal areas by supporting biodiversity and improving water quality.

They’re also an important resource in efforts to mitigate climate change as they absorb large amounts of carbon dioxide. Although they only cover about 0.2% of the planet’s seabed, seagrasses account for about 10% of the carbon our oceans store, but unfortunately they are being lost at an alarming rate globally.

Recent seagrass research

Up until recently, it was thought that seagrass flowering was very rare in the New Zealand species of seagrass, but recent research by Cawthron Institute and others has revealed that isn’t the case. New Zealand’s species of seagrass does have flowers, which are more difficult to spot than species found in other parts of the world.

Last summer Cawthron scientists found lots of seeds and flowers in Nelson Haven and managed to get one of the seeds to germinate for the first time in Aotearoa. This suggested it might be possible to restore seagrass meadows in New Zealand at the scales required to achieve meaningful carbon sequestration results using seed-based techniques that we plan to develop.

The amount of carbon a seagrass meadow stores can vary depending on the species and the environment it is situated in, but overseas studies have shown that some meadows can sequester carbon up to 27 times faster than forests on land.

The outcomes of this seagrass restoration project could inform future work on blue carbon initiatives in Aotearoa New Zealand.