Protecting the Tasman Bay is crucial for ocean health, says the man taking on a kaitiaki role
Marine Ecology

Protecting the Tasman Bay is crucial for ocean health, says the man taking on a kaitiaki role

The spotted shag can dive to depths of 40 metres.

Braden Fastier

The spotted shag can dive to depths of 40 metres.

On a winter’s day last year, Stew Robertson saw a right whale scratching an itch in the shallows of Onetahuti Beach in Abel Tasman National Park.

“It looked like a log, being rolled by the waves. But the water was calm, and when I got closer, I saw it was a whale, scratching its back on the sand.”

Our ocean's health hangs in the balance, with over fishing and sediment build up having a huge impact on the creatures who live in the Tasman Bay.

Braden Fastier

Our ocean’s health hangs in the balance, with over fishing and sediment build up having a huge impact on the creatures who live in the Tasman Bay.

The director of Abel Tasman Eco Tours, Robertson is our captain for the day, on a tour offering a deeper look at the ecology of Te Tai Tapu, the sacred coast. As he steers the water taxi away from Marahau and out along the coast, a fresh southerly has the passengers, visitors from the UK and France, hunching their shoulders as the boat picks up speed.

While itchy-flanked whales are a jaw-dropping site, the delicately balanced ecology of the Tasman Bay is no less spectacular, Robertson says.

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He points out a hangout of spotted shags, preening on a rock. 

“I reckon shags are pretty special,” he says. “They can fly at 50 kilometres per hour, and dive 40 metres by swallowing stones.”

Stew Robertson has loved the ocean since he could walk. Now, he's passing on his passion to a new generation of children.

Braden Fastier

Stew Robertson has loved the ocean since he could walk. Now, he’s passing on his passion to a new generation of children.

The guano that runs off the rocks helps fertilise the seaweed. However, a few weeks ago, diving across 32 sites around the bay, Robertson found plenty of sea urchins, but little seaweed: a lack of predators has allowed the echinoderms to flourish unchecked.

“You can artificially remove the sea urchins, but the main thing to do is address over fishing.”

For the marine conservationist, showing people around the coastline is more than a tourist moneymaker, it’s a way to highlight the park’s precarious ecosystem. Two years ago, he and a team of like-minded conservationists began Tasman Bay Guardians, a charity aiming to spur a generation of school children into taking on a kaitiaki, or guardian role of the Tasman Bay.

The lush greenery of Abel Tasman National Park provides a backdrop for the day-long tour.

Braden Fastier

The lush greenery of Abel Tasman National Park provides a backdrop for the day-long tour.

Robertson crouches down and pulls out a copy of Subtidal Invertebrates of New Zealand from the small library he stows on board. He uses the books to double check a name, or illustrate a fact about one of the species you’re not likely to see from above water.

He taps a picture of a blue cod. “The male blue cod’s job is to annoy the female, keep her cortisol levels high. Female blue cod will revert to male when cortisol isn’t present, and it’s a one way street: when they are male they don’t go back.”

Robertson’s career began in 2002, when he landed a water taxi job within a week of moving to New Zealand from Scotland.

A few years later, he studied marine biology, and later started Abel Tasman Eco Tours, pitching to locals and tourists with a deeper interest in the local ecology. 

What we do on land impacts upon our oceans, Robertson says.

Braden Fastier

What we do on land impacts upon our oceans, Robertson says.

The changes he’s seen during his 17 years on the water have been dramatic.

Native forest has regenerated, and better management under Abel Tasman’s Foreshore Reserve Management plan has meant tourism has less of an impact on the park. 

Some sea life has come back. 

“There’s a lot more Hector’s dolphins now; once I saw 25 in one go.”

But warming water and climate has led to a decline in other species, or changing behaviour patterns, like the white fronted terns we can see, skimming over the water.

Through his non-profit Tasman Bay Guardians, Stew Robertson hopes to inspire a generation of children to take on a kaitiaki, or guardian role, caring for our oceans.

Braden Fastier

Through his non-profit Tasman Bay Guardians, Stew Robertson hopes to inspire a generation of children to take on a kaitiaki, or guardian role, caring for our oceans.

“They’re not usually here in the winter, they go to Australia.”

The sea has begun to encroach on the land, breaching the high tide mark several times during the last two years and putting the future of the park’s DOC campsites in jeopardy.

Robertson’s in just about every local conservation group going. He plants trees, organises beach clean ups and traps predators. When he dives, he dives with a purpose, counting sea urchins or kina, or monitoring seaweed. 

“I always like to have a mission.” 

He’s not alone. 

“The volunteer culture in the park is incredible. There’s so much pest control, weeding and planting, people doing it for the love of it.”

The sea bed beneath us has undergone a drastic transformation since the 19th century, when it was “crusty and alive”, Robertson says.

Stew Robertson hopes that through Tasman Bay Guardians, he can inspire a generation of children to take on a kaitiaki role, caring for our oceans.

Braden Fastier

Stew Robertson hopes that through Tasman Bay Guardians, he can inspire a generation of children to take on a kaitiaki role, caring for our oceans.

Over time, silt and sediment run off from intensive land use: forestry, roading and housing developments has built up on the sea bed.

“There’s a lot of pressure from the land, fishing, tourism, recreational use, mining; it all has an impact.”

Robertson points to his arm, just below his shoulder.

“Most of the places I go, [the sediment] is this deep, it’s really murky. It’s reached a tipping point and it can’t go back.”

The quiet inlets and bays along Te Tai Tapu hold a wealth of hidden treasures.

Braden Fastier

The quiet inlets and bays along Te Tai Tapu hold a wealth of hidden treasures.

A short distance away in the national park, however, the sea bed looks different. Filtered by the trees, the water is clearer. Without sediment, the light can get through and seaweed can grow.

Robertson has watched life explode in the marine reserve, a protected slice of the Tasman Bay created in 1993.

The Tasman Bay waters are full of surprises. Stew Robertson once saw a whale scratching its flanks on Onetahuti Beach.

Braden Fastier

The Tasman Bay waters are full of surprises. Stew Robertson once saw a whale scratching its flanks on Onetahuti Beach.

He looks out at the trawlers traversing the reserve’s perimeter, waiting to catch the fish that travel over the invisible boundary.

“A lot of people who were against the reserve can now see that it’s beneficial, as the overspill can be caught as [the fish] come out of the reserve.”

However, the 1835 hectare area isn’t nearly big enough, he says.

Pied shags stand sentry in Abel Tasman National Park.

Braden Fastier

Pied shags stand sentry in Abel Tasman National Park.

“We’re deemed to be one of the world leaders in conservation but [in the Tasman Bay] we protect less than one per cent of our waters.”

Studies show that large protected areas create resilience. Ideally, the protected portion should be around 30 per cent, Robertson said. 

A significant part of Tasman Bay Guardians’ work is with schools.

Robertson takes children onto the water, teaching them to snorkel. 

“Some of the children [we teach] have never even seen a seal before.

During winter, few tourists visit the park, and Onetahuti Beach is almost free of footsteps.

Braden Fastier

During winter, few tourists visit the park, and Onetahuti Beach is almost free of footsteps.

“Parents see how their kids respond to being in a place of abundance; it blows them away.”

On land, a team of teachers run sessions showing children how their actions can impact the ocean in programmes about waste water, or whitebait.

While Robertson says children are more informed about the environment than he was at the same age, there are still plenty of knowledge gaps.

The message is pretty simple: everything we do matters, and with small changes, we can minimise our impact.

“Plant trees, be aware of where rubbish is going, rubbish is here to stay. A lot of people don’t realise water goes down their drain doesn’t go into the sewer, so wash your car on the grass instead of on the road. Even the type of sunscreen you use has an impact.”

Abel Tasman Eco Tours takes a deeper look at one of New Zealand's most popular tourist spots.

Braden Fastier

Abel Tasman Eco Tours takes a deeper look at one of New Zealand’s most popular tourist spots.

Interest is strong, with demand for the programme outstripping the Guardians’ capacity, Robertson says.

To raise funds for the non-profit, Robertson’s planning to offer koha trips. “People can pay whatever they can afford, so people who wouldn’t usually do it can go.”

By revealing some of the magic he experiences on the water, Robertson hopes future generations will be inspired to take on that vital kaitiaki role, securing the future of Te Tai o Aorere.

“It’s the most amazing place to live and learn and play. But we need to take better care of it. And that’s why we target the kids, in the hope the next generation make better decisions.”  

The Nelson Mail