Where the southern Alps meet the sea on the west coast of New Zealand’s rugged south island, Hinerangi Barr and her whanau (family) hold a tribal story like no other: the landing place where Maui, hero of the Pacific, took his first steps on Aotearoa.

It is not a well-known story, even to New Zealanders, but it’s sacred to this small sub-tribe of Ngāi Tahu, Kāti Māhaki. Two years ago, a large contingent of the creative team of Te Papa – New Zealand’s national museum – ventured 700 kilometres south to sleep on the floor of the tribal marae (meeting house) and record the story of Maui’s landing for an audience that will eventually number in the millions.

“We were quite overwhelmed,” remembers Barr, who wears two stones of pounamu at her throat and wrist, in shades of unusual turquoise.

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“It was a bit confronting to consider having our story told at Te Papa, on this huge scale. We wanted to share the story but we also felt a bit anxious – how could we also protect the story?”

On Saturday, Te Papa will unveil its biggest development since its inception 21 years ago, the result of the largest ever investment in a museum exhibition in the country. Te Taiao Nature, a NZ$12m permanent nature zone, explores New Zealand’s natural environment, from Maui’s first landing on the pristine coast at Bruce Bay, to the threat of predators, climate change and pollution in the modern world.

A 700-year-old fractured moa egg sits at the heart of the exhibition, cocooned in a 70-square-metre, four-metre-high bird’s nest woven from recycled materials. Inside, the songs of native birds extinct and threatened surround you, some now calling from the grave.

Facebook Twitter Pinterest By placing their hands on a carved touchstone, visitors can use their mauri or life-force to add life to the landscape on the interactive screen. Photograph: Maarten Holl

It is hoped the bird’s nest will inspire New Zealanders to tap into their role as kaitiaki (guardians) of the land, and motivate them to step up to protect their homeland at a time of unprecedented environmental threats and bio-diversity decline.

Completely dual lingual, the exhibition weaves Indigenous knowledge and western scientific discoveries seamlessly, giving neither the upper hand, but presenting them as complementary to a robust and deep understanding of the country’s unique natural environment, which evolved in isolation over millions of years.

At a time when museums around the world are struggling with how to become more diverse and inclusive, Te Papa is leading the way in its symbiotic relationship with New Zealand’s Indigenous people. Bi-culturalism isn’t an afterthought at Te Papa – it’s the institution’s life blood.

“I think the Māori world view and the scientific world view interact with a lot of respect here,” says Barr, who considers Mt Cook an ancestor, the roaring west coast rivers as whanau, and the rainforests of South Westland as living, breathing relatives.

'We've still got a long way to go with valuing Indigenous knowledge, but it’s getting stronger and stronger.' Hinerangi Barr

“It was amazing watching Te Papa’s entire design team come down to this quite remote place. It’s about them honouring their foundations and honouring their treaty of Waitangi obligations. I think we’ve still got a long way to go with valuing Indigenous knowledge, but it’s getting stronger and stronger.”

Dr Susan Waugh, Te Papa’s head of science, shies away from calling the exhibition a display of activism from a state-funded institution, but admits her team chose to feature environmental issues that visitors would feel capable of taking action over, such as New Zealand’s degrading freshwater quality, and plastic pollution.

It is Waugh’s hope that her team will one day be forced to remove parts of Te Taiao as they become out of date; that the unswimmable rivers of the north and south islands will become summer hotspots again, just as the Labour coalition government has promised.

Facebook Twitter Pinterest ‘I don’t see us as having an agenda but rather recognising a reality,’ says creative director Frith Williams. ‘We need to take action now.’ Photograph: Maarten Holl

Waugh says Te Papa was founded on bi-cultural principles, and the process of telling the full story of New Zealand’s environment – from modern day climate change threats to the diminishing bird calls of the bush – is enmeshed in the institution’s DNA, even if, at times, views can be “stridently different”.

“In terms of the way Māori approach the world it is an observational science – they have had a lot longer to work on it than we have,” says Waugh.

“The Māori relationship with nature is one of 700 years of exploration and discovery. That knowledge has a lot to teach all planetary citizens; about what is fragile, about how the eco-system responds to different pressures.”

Of the 1200 collection items on display the oldest specimen dates back 140m years; a giant ammonite, a shelled relative of the squid. For Brad Haami, the Mātauranga (knowledge or wisdom) Māori adviser, working on the exhibition over the last two years has unearthed Indigenous knowledge that might otherwise have been lost.

“Humanity is the youngest of the entities of the natural world. The plants and animals are the elders and it’s our role to learn from them, and care for them,” says Haami, who, like 70% of Māori people, is a city-dweller.

A lot of our views about nature are very different, but our beliefs of mitigating the risks for the future are the same. Brad Haami, Mātauranga Māori adviser

“I hope people will come away with an understanding that Māori as a people have our own different way of perceiving nature, [which is] just as important as a scientific view of nature. And often what our ancestors said the scientists are only just finding out now.

“A lot of our views about nature are very different, but our beliefs of mitigating the risks for the future are the same – and that’s a huge commonality.”

For creative director Frith Williams, it was important that the exhibition does not become a “to-do” list for visitors; another guilt-laden, information heavy tour of the destructiveness of the modern world, the massive bio-diversity loss, and the very real threat of climate change, especially in low-lying regions, where many marae are located.

Williams hopes visitors will first be enchanted by the charms and quirks of the New Zealand environment – the over-sized and gawky moa, the hot-fire pathways of geo-thermal activity, and the pungent smell of a fossicking Kiwi – before feeling inspired to save it.

In preparing Te Taiao, Williams and her team studied behavioural psychology and what motivates change. While the debate on museum neutrality rages around the globe, Te Papa has picked a side – and made the quiet passivity of museums past a distant memory.

“Social-ness is very important in a museum. But it is also very important in terms of taking action,” says Williams.

“It’s not always appropriate for a museum to state an opinion, but in some contexts maybe it is. I don’t see us as having an agenda but rather recognising a reality. So yes, the museum is bold enough to say, ‘We need to take action – now’.”

• Te Taiao Nature is now open at Te Papa Tongarewa, New Zealand’s national museum in Wellington

• The Guardian visited Te Papa as a guest of Wellington NZ