Conservation Minister Tama Potaka has likened the “catastrophic” caulerpa seaweed invasion to the cattle disease Mycoplasma bovis — which led to one of the country’s biggest biosecurity responses and the culling of 176,000 cattle.
Potaka’s comments came after visiting the Bay of Islands to see firsthand the “disastrous and catastrophic” impacts of the super-spreader caulerpa seaweed.
He visited the biggest mainland caulerpa infestation at eastern Bay of Islands Omākiwi Cove this morning, in the wake of 500 tonnes of caulerpa washing ashore due to high winds and waves of ex Tropical Cyclone Tam over Easter.
Potaka said caulerpa’s impact was “disastrous and catastrophic” on beaches and the health of the whenua, and clearly impacted the wairua of the environment.
Caulerpa is a super-spreader seaweed that can grow from a tiny bean sprout fragment to cover a rugby field-sized area of seafloor within three months in the right conditions.
Potaka said was a serious invasion issue like Mycoplasma bovis or freshwater golden clams, where a joint response was needed.
Eradicating the cattle disease from New Zealand led to one of the country’s biggest biosecurity responses costing $880 million over a decade. Around $12 million has been spent on New Zealand’s freshwater gold clam invasion to date.
Potaka said he would be speaking to Biosecurity Minister Andrew Hoggard upon his return to Wellington, his efforts supporting biosecurity efforts.
The Conservation Minister met Te Rāwhiti hapū working to fight the caulerpa invasion so he could visit kanohi ki te kanohi (face to face).
“It was important for me to be here to see people on the ground dealing with it on a daily basis.”
Potaka had never seen caulerpa first-hand and said it was worse that he had imagined.
The tonnes of caulerpa washed up onto Omākiwi Cove and Whiorau Bay are now heaped into huge 150 metre-long piles, originally up to 1.8m high, at the head of these beaches.
Locals rushed to remove the seaweed from the shoreline before it washed back out to sea creating huge new infestations.
He said exotic caulerpa was a massive incursion and the Government was taking steps to deal with it, but getting rid of it would not be a one-shot wonder.
Caulerpa’s effects went beyond the environment as it impacted the economy and intersected with identity, culture and society.
He said the time and resources the community had put into fighting caulerpa was impressive.
Potaka also met Bay of Islands ocean engineer Andrew Johnson in Paihia.
Johnson is leading the development of New Zealand’s first large-scale underwater tractor unit for removing caulerpa infestations from the sea floor. This work was recently boosted with a $6.2 million Government grant.
Potaka said innovation such as this was something he was particularly interested in.
He said Northland/Te Tai Tokerau was a beautiful place everybody should visit. Dealing with caulerpa was important in that context.
Exotic caulerpa was first identified in New Zealand at Great Barrier Island in 2021. Its first mainland infestation was confirmed in the Bay of Islands in 2023.
Local Democracy Reporting is local-body journalism co-funded by RNZ and NZ On Air.
