Viewpoint – Climate action with mussel

With the release of the Intergovernmental Panel on Climate Change Special Report on Global Warming of 1.5°C, every action must be a meaningful climate action.
In the Mahurangi Harbour, the mobilisation has already begun but with an action few would readily see as climate action, until taking a look below the surface.

By the mid-1960s, dredges had effectively eradicated the Hauraki Gulf’s 500 square kilometres of green-lipped mussel reefs, and in the half-century since, the seabed of the gulf remains essentially barren. But, as trials in the Mahurangi Harbour and elsewhere have demonstrated, this can be turned around, by depositing surplus, oversized mussels, obtained from Coromandel mussel farms.

The prime motivation for re-establishing the beds is that before they were so fecklessly removed, they filtered the entire gulf water column every 48 hours.  

But the green-lipped mussel is miraculous. It is not just a filter for clarifying water, it is also a double-acting climate-action carbon dioxide sequestering machine. By clarifying the water column, sunlight penetrates deeper, growing more phytoplankton, which, like leaves, absorbs carbon dioxide, expels oxygen, and takes dissolved carbon out the atmosphere.

Formed as Friends of the Mahurangi in 1974, Mahurangi Action is making climate its middle name by supporting a five-year, potentially $1 million, Mahurangi-based green-lipped mussel reef restoration research project managed by Auckland University’s Dr Andrew Jeffs. Dr Jeffs delivered the August Warkworth Town Hall Talk, part of an ongoing series initiated by Mahurangi Action and One Warkworth and supported by Mahurangi Matters.

The project will employ two PhD students whose mission will be to develop more cost-effective methods for establishing mussel reefs than have been used to date. Using mature mussels, even when supplied at cost, is prohibitively expensive, costing about three times as much as planting native trees. At these prices, replacing the gulf’s mussel beds en masse would cost about $50 billion. The last truckload of mussels, which created five small beds in the Mahurangi at mates’ rates, cost $80,000. Clearly, far smarter means must be developed for mussel reef restoration to make a meaningful difference.
Meanwhile, for the hard-shelled climate cynic, there is lots to love about seafood and eating it – given that the mussel reefs already established are making heart-warming nurseries for juvenile snapper, right here in the Mahurangi.

Tessa Berger, Rodney Local Board
tessa.berger@aucklandcouncil.govt.nz