What would shifting much of Auckland’s freight shipping operation do to Whangārei’s harbour? Conservationists say the risks are like throwing dice for the marine ecosystem.

Conservation advocates worry rerouting ships from Ports of Auckland to Whangārei’s Northport might stimulate the local economy but come at a cost to the harbour’s ecosystem.

The proposed shifting of the port is now a bottom line for New Zealand First in any possible future coalition agreement. After announcing his candidacy for the Northland electorate last week Shane Jones told TVNZ’s Q+A: “In the event that we’re back, a bottom line is definitely going to be the relocation of the Ports of Auckland to the north.”

But there’s concern from conservationists and scientists that more ships in Whangārei Harbour would mean more dredging, construction, noise pollution and potential ship strike as well as a change to water flows.

Northport chief executive Jon Moore’s response is that, unlike other ports Northport is accustomed to working with environmental rules and is the only port in the country to be built under the Resource Management Act.

“This means that all of the environmental management requirements of the RMA have been built into the port’s day-to-day operation,” he says.

Build it and they will come

While Northport may have established itself within RMA rules, compared to the Auckland’s waterfront operations it’s small fry. Currently just three ships at a time can tie up at Northport. In Auckland, depending on the size of the ships, there’s space for 11 to 13. 

The number of ship calls per year also shows the gap between what the two ports are handling at present.

In the last financial year 1318 ships called in at Ports of Auckland (POAL). Around 127 were cruise ships and a few were Navy ships, but the majority carried freight.

Northport had 304 ship calls in the same time period. The nearby refinery, which uses its own berth a short distance from Northport, had 218.

To take even some of Auckland’s ships would require a substantial expansion. 

Northport already has a resource consent to extend its 570 metre berth by 270 metres and reclaim 2.8 hectares of land but this small extension won’t come close to providing enough berths to cater for Auckland’s ship traffic.

A video on the Northport website showed potential options for expansion with six ships berthed. If completed in total this would add another 820 metres of berth extending either side of what currently exists and reclaim 25 hectares of land from the harbour. 

Given the current conversations, it’s perplexing there’s no option on Northport’s vision of the future video which shows how much the port might need to expand to cope with its current ships as well as Auckland’s freight ships.

Even to fit the depicted three more ships would mean a big change in a small harbour which conservationists say has some outstanding features. 

Also consented is deepening of the channel into the harbour. This dredging consent for 3.6 million cubic metres of sea floor is held by the oil refinery, not Northport. This is to ensure the channel is deep enough for larger ships. Newsroom understands while the work was consented in 2018 it has not yet begun.

A marine reserve sits just 650 metres from Northport and is home to seahorses, dwarf scorpionfish, octopuses and attracts predatory fish such as kingfish. The harbour also has significant shellfish beds.

There will be dredging

Based on the option shown on the video Northport’s, CEO Moore estimates it would “need to remove 1.14 million cubic metres (not a large amount as far as dredging operations go) to create a consistent depth of 14.5 metres from the western end of the berth to the eastern end” of the berths pictured. 

This is in contrast to what’s said the report of the Upper North Island Supply Chain Strategy Working Group published in December 2019. This was not written by Northport. It claimed while Auckland needed dredging to fit larger ships: “No such dredging is required at Northport as Suezmax ships already visit.”

Staff at POAL have estimated the dredging required in Auckland versus dredging which might be required at Northport. The estimation includes the channel dredging at Northport which the oil refinery already has consent for. For POAL the ability to dredge the channel is dependent on resource consent hearings this month.

Estimation by Ports of Auckland of potential dredging required. The 3.7 million cubic metres of channel dredging for Northport is already consented for Refinery NZ to undertake.

Local ocean ecologist Glenn Edney said the amount of dredging potentially needed to cope with Auckland’s ships as well as what is already expected in Northpoint was likely to be unprecedented in the harbour. 

The process would involve dredges suctioning sediment which has settled to the seafloor and placing it onto barges. During the process some can spill out.

“A lot of the dredging is fairly toxic. While it’s in the mud it’s trapped there and it’s relatively harmless. It’s only when it’s suspended in the water or on the surface it becomes a problem and of course that’s what dredging does,” Edney said.

Another effect of dredging is a likely change of water flow in the harbour as areas are deepened. This could affect the water flow around the marine reserve as well as the shellfish beds.

He’s sceptical of the ability of modelling to accurately predict the outcome.

“The environmental impact models will be standard models that will look at water flow and everything. Unfortunately the complexity of a dynamic living system like Whangārei Harbour defy our ability to model really accurately. We’re throwing the dice on the health of those significant shellfish beds.”

As well as water flow changes from dredging, Edney worries about the potential of silt stirred up by ship propellers. Shellfish are known for being filter feeders which can clean water, but they don’t cope well with silt suspended in water.

He said the shellfish are already struggling and there’s a rāhui on collecting them.

There’s a flow-on effect from shellfish abundance which impacts other sea life.

The shellfish attract stingrays to the harbour and females come to the harbour to give birth.

“When the stingrays are born, beautiful, cute little 25 centimetre replicas of the adult, the first thing they do is they go straight down to the sea floor in those shallow harbours and they feed on the young shellfish.”

Orca in front of Marsden Point refinery. Photo; Ingrid N. Visser

It’s a case of pipi starting a food chain. While shellfish are a tasty lunch for stingrays, the stingrays’ oil-filled livers are a tasty treat for orca.

Listed as ‘nationally critical’ by the Department of Conservation, New Zealand’s orca are at the last stop on the threat classification system before extinction. Only 150 to 200 remain.

Marine biologist Ingrid Visser is based in the area. She’s part of the Orca Research Trust and like Edney she sees the ecosystem effects as a stack of cards.

“It’s not just pick-a-species, they’re all interconnected.”

She also worries about the impact of dredging on the harbour as well as noise, pollution and the risk of boat strike.

“We know that the orca, for instance, use it [Whangārei Harbour] for socialising, for mating, for giving birth, for feeding, for sleeping. It’s critical habitat for them. People say ‘they can just go somewhere else’. Well, no. They can’t because there are very few harbours left they can go into.”

Ship strike – marine hit and runs

Another concern is the increased likelihood of ‘ship strikes’. Just like when bugs make an unfortunate connection with a travelling vehicle’s windscreen, sometimes whales and other sea creatures collide with ships. Most of the time, the far larger ships don’t even realise they’ve hit a whale. 

University of Auckland Associate Professor Rochelle Constantine explains that instead of hearing ships only when they’re close, the constant low frequency hum of ships can be heard underwater for many kilometres and the sound doesn’t get a lot louder as ships get close.

There’s a possibility this continual thrum becomes little more than background noise for sea mammals such as the Bryde’s whales she studied in the Hauraki Gulf and they tune the sound out as they go about their normal day of eating plankton.

“Our work showed that on average, just over two whales per year were being killed by ship strike. Those were just the whales that we found. So we knew there were probably more.”

Like orca, Bryde’s whale numbers are limited to the just below extinction point. Two ship strike deaths a year posed an enormous threat to the species, Constantine said.

She has worked on a voluntary protocol with the Hauraki Forum, the shipping industry including Ports of Auckland and the Environmental Defense Society.

By reducing speed to 10 knots in the Hauraki Gulf in areas whales were known to be in, the deaths stopped. Collisions probably still occur, said Constantine, but at 10 knots, they’re not as likely to be lethal. 

Since the voluntary measures were adopted by the shipping industry the last recorded death was in 2014. 

“In my ideal situation of looking at the environmental impact, the voice of the harbour would be at the table. That voice would be saying, ‘there’s too much uncertainty’.”

Constantine hopes any proposal to divert ships to Northport includes work to understand the sea life in the area.

“Before any of this occurs we would need to undertake a really good census of the habitat use in those waters coming into the Northport region to understand the main routes that ships will take into that port and then have a look and assess the risk profile.”

She said she had been involved in aerial surveys in the past up to Whangārei Heads and knows Bryder’s, blue, fin, sei, humpback, pilot and minke whales can be found in the area, as well as several dolphin species.

“It would be such a shame to undo all the hard work that’s been done over the last seven years. There are 15 whales alive today because the ships slowed down.”

Constantine also wonders about the impact of construction efforts on the harbour, saying the importance of the seabed is under-appreciated.

She said there was a difference between a localised, brief, disruption to one which is ongoing, never-ending or regular.

“Is more dredging required? Are they going to be making larger wharves that change the water flow? All these kinds of dynamics that make noise in the water, they result in shifts in sedimentation, destroying the seabed to make the port deeper.”

Vissner acknowledges work by Northport.

“Credit where credit’s due. Northport has been doing due diligence looking at what they can do to mitigate the issues. There’s a difference between mitigation and complete abstinence. We don’t have complete abstinence in the harbour at the moment, but that doesn’t mean we should be expanding it either.”

Edney wonders what the conversation would be like if the harbour enjoyed the same legal personhood as the Whanganui river and, through spokespeople, the opinion of the harbour was required to be taken into account.

“In my ideal situation of looking at the environmental impact, the voice of the harbour would be at the table. That voice would be saying, ‘there’s too much uncertainty’.”

Images from Northport’s website related to possible future options to expand the port. Move the slider to view the current port and a potential expansion.

Leave a comment