Exotic caulerpa’s spread to several sites in the Hauraki Gulf, the Coromandel Peninsula and the Bay of Islands has prompted fears of a looming environmental disaster for New Zealand.
Exotic caulerpa’s spread to several sites in the Hauraki Gulf, the Coromandel Peninsula and the Bay of Islands has prompted fears of a looming environmental disaster for New Zealand.
The economic toll of a super-spreading seaweed - known as the world’s worst marine pest - on Auckland’s ‘blue backyard’ is at least $150m, new analysis finds.
Notorious for rapidly blanketing areas of seafloor and smothering life, the bright-green exotic caulerpa’s spread to several sites in theHauraki Gulf, Coromandel Peninsula and Bay of Islands has prompted fears of a looming environmental disaster for New Zealand.
The worst-hit area remains Aotea/Great Barrier Island, where the foreign species was first found in 2021, and where officials have put in place restrictions for boaties.
Despite efforts to control it – such as using machinery to suck it directly from the seafloor – authorities say that national-scale eradication likely isn’t feasible.
Now, a report by the New Zealand Institute of Economic Research has revealed the economic impact of its incursion in the gulf.
The report estimated its impact in the Hauraki Gulf was up to $109 million for commercial and recreational fishing – with a cost of up to $45 million on the gulf’s biodiversity.
But those were still considered “best-case” estimates and there were impacts in several areas – such as the invasion’s toll on recreation, tourism, shipping and mitigation – that couldn’t yet be quantified in dollar terms.
Prepared for the Hauraki Gulf Forum, the analysis also stated the value of ecosystem services and natural capital in the marine park – where 19 new protected areas are about to be established – at more than $5 billion each year.
Exotic caulerpa seaweed washed up at Okupu Beach, on Aotea/Great Barrier Island, after Cyclone Gabrielle. Photo / Noel Nancekivell
Auckland Mayor Wayne Brown said the costs cited in the report were frustrating.
“I’m a boatie before I’m Mayor and I have already put a heap of advocacy into cleaning up this invasive weed,” he said.
“To see this huge financial cost, it’s extremely frustrating.”
Brown said that, beyond solutions like dredging, he believed more could be done to tackle it.
“These costs provide an economic argument for this.”
Hauraki Gulf Forum co-chair Nicola MacDonald said the Government’s recently-announced $10m funding boost for control efforts was welcome.
“Among the challenges facing the Hauraki Gulf, the spread of the invasive exotic caulerpa is the greatest threat facing our marine ecosystem, smothering vital marine habitats, threatening the biodiversity and fisheries of the gulf.”
The report comes weeks after divers discovered a patch of the seaweed at Leigh’s Omaha Cove – a short distance from nationally-renowned Te Hāwere-a-Maki/Goat Island Marine Reserve.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
