A Shore Thing: Great Barrier Island, Auckland's shrinking motu

Thursday, 23 December 2021

Great Barrier Island sits just 90km northeast of Auckland, in the Hauraki Gulf. With its exposed coastline, it’s an area susceptible to coastal erosion, with everything from the roads to cultural sites in peril. (First published January 2022)

Auckland has 3200km of coastline, and as sea levels rise and cliffs erode, some 17,600 of the region’s homes lie in harm's way. A Shore Thing is a Stuff series that talks to the people whose properties are threatened, the scientists attempting to warn us, and the engineers trying to hold back the ocean.

It may only be a half an hour flight from central Auckland, but Great Barrier Island feels worlds away.

Palm covered, littered with white sand beaches and ringed by sparkling cyan-blue waters, the little droplet of land emanates an air more akin to the breezy Cook Islands than the City of Sails.

Yet beyond the postcard image there is a quiet battle taking place, as locals brace themselves against climate change, rising sea levels and the effects both are having on the coast.

Puriri Bay in Great Barrier Island. The island has the Auckland region’s lowest Covid-19 vaccination rates.

* Covid-19: Waiheke and Great Barrier Island closed to visitors at level 3

* Auckland's Waiheke Island seeks Dark Sky sanctuary status

Tryphena Wharf, where Shoal Bay Rd begins.

Great Barrier Island’s exposed coast makes it one of Auckland’s most susceptible areas to erosion and instability. With its 285 square kilometres slowly being nibbled away by the waters, there are risks to the safety of property and infrastructure, alongside various cultural and environmental sites.

On a map, Shoal Bay Rd snakes the western side of the island.

Flanked by the Hauraki Gulf on one side and dense bushland on the other, it is the motu’s aorta: a tar-sealed road that travels from the main wharf to the island’s north and offers a gateaway to the area’s main store and café.

At its starting point in Tryphena, the road meets the water in dangerously-close proximity. A roadside edge marker teeters the rocky fringe. When the weather is rough and the tide is high, the ocean’s waters are known to overtop the banks and spill across the length of the road.

Aotea Great Barrier Island local board chairwoman Izzy Fordham says the shelter’s cost is “excessive”.

“The road here is actually slipping away, and it is definitely a concern,” says Izzy Fordham, Great Barrier local and chairwoman of the island’s local board. She points to the seawall, where there is evidence of undermining by waves, and looks back up at the road, just mere centimetres away.

In recent years Fordham has witnessed the demise of the thoroughfare, which curves around the corner and transforms into Puriri Rd, accelerating at an alarming pace. Yet while discussion of the issue with the wider Auckland Council and Auckland Transport has become more commonplace, a solution is still to be reached.

She says they are in talks about rerouting or setting back Shoal Bay Rd, but that in itself brings challenges.

“The topography here is really rocky, so it's not going to be easy to just build another road, or set the current one back,” she says, adding how, if it were to be set back, it would put a nearby historical wall in danger. Both options raise nerve-wracking questions on the how, and the cost.

The wider Auckland Council has recently kickstarted the development and coordination of its Shoreline Adaptation Plans, which look to respond to coastal hazards and climate change over the next 100 years.

The work is being rolled out around the Auckland region on a prioritised basis in partnership with mana whenua, and there are a few places - like the mainland’s Whangaparoa region - that are due to come before the Great Barrier, despite the area’s dire need for attention.

The urupa, marked by a flourishing pohutukawa, now sits behind a protective rock wall.

“The Hauraki Gulf Islands are planned to be investigated in future years,” says Myles Lind, head of asset management.

“Auckland Transport is investigating interim solutions for specific roading protection needs around its network, and this includes the Hauraki Islands.” Lind says the work will be “coordinated with existing road maintenance programmes” and can be expected soon, but a specific date is not yet known.

Further north, the Pacific Ocean is encroaching around the coast and putting more than just the pavement in peril.

An ancient Māori burial site on the northeastern foreshore, close to Motairehe marae in Katherine Bay, is a particularly poignant reminder of the issues rising sea levels are raising.

Peter Hoey atop his iwi’s urupa close to Motairehe marae, in the northern region of Great Barrier Island.

The waters here have been gouging into the local urupa and unearthing a pohutukawa with it - an act that is not only detrimental to the beauty of the landscape but to the cultural value of it, as the stoic tree serves as an iwi-recognised landmark for the cemetery that lies below.

Forced into action by fears that the koiwi of their ancestors would be washed out to sea, the Motairehe Marae Trustboard, with support from the landowners, hired an island contractor to put a rock boulder sea wall in place just over twelve months ago.

It is a successful solution but a short term one, and one Fordham has concerns of it only being “a band-aid.”

Dr Mark Dickson, a coastal erosion scientist from the University of Auckland, says one of the main problems with seawalls like this is the expectation that when it is built, it will be there for good.

“The reality, however, is that defence structures have a design life, usually less than 50 years,” he says, adding how the structure may have unforeseen adverse effects, and it isn’t yet known whether it will be economic to rebuild it at some point in the future.

Relocating the urupa might seem like a more viable long-term option, but with questions around when, where and how - not to mention navigating the distressing aspect for local iwi - it isn’t an option that should be considered lightly.

Plus, locals in these parts have already had to make enough changes to cater to the threat of changing weather patterns.

Peter Hoey, Mana Whenua o Aotea and now trustee of Motairehe Marae, describes how members of his whānau have had to rebuild their homes higher to protect against flooding, and he says there are talks among the other marae trustees about raising Motairehe itself one or two metres.

In the past 15 years alone, Hoey has witnessed growing hints of climate change.

Some which may go unnoticed to those unfamiliar with the island - like the shifting of timing with bird migrations and the flowering period of trees - others which are alarming even to the uninitiated, like freak weather events happening every few years rather than once every few decades.

“A few years ago we had a small tidal wave come in, and we’ve had two or three tsunami warnings in recent times,” he explains.

“We’ve had one big flooding recently, and there have been plenty of large storms - some where the rain has been so heavy and consistent it’s resulted in huge slips on cliffs at the top of the island.”

Hoey says the rock wall was a step in the right direction, but a wider conversation, in partnership with Auckland Council, Department of Conservation and Aotea Local Board, on mitigation and precautionary methods is still something yet to take place.

“To actually sit down and have a hui about it and mitigate future risk is still something that still needs to be done.”

On conversations such as these, Dickson says we need to make an active shift away from talk of positions of ‘retreat or defend’ because, for coastal sites like Great Barrier and beyond, we will more likely end up transitioning between various management options.

“We’re going to need to defend some locations in perpetuity because the assets and infrastructure are simply too valuable or too important to society. In other places where there are very limited assets it should be relatively easy to make pragmatic decisions to retreat,” he says.

As a small island with a population of just over 1100, with some areas dense in coastal habitation and others only beaches and vegetation, Great Barrier is an example of how both retreating and defending will need to be enforced.

While the specifics of the conversation remain to be seen, the fact that locals, iwi and the council are pushing for it may herald a change in the near future.