This Is How It Ends: Why our forest 'lungs' are dying

Tuesday, 26 October 2021

They are our lungs. But New Zealand’s treasured native forests are facing a range of deadly threats, including kauri dieback, myrtle rust and exploding deer numbers. Andrea Vance and Iain McGregor report, for Stuff’s This is How it Ends series.

On the very edge of New Zealand stands a forest of memories. Ancient kōpi trees, carved with symbols of meaning and depictions of long-dead Moriori ancestors, have stood long after the stories are forgotten.

But the trees are dying, another blow to the island people who have already lost much of their history and culture.

Since the 1940s, more than 1000 rākau momori have been lost, with the remnants fading away.

The loss of mature kōpi is the result of 19th century land clearance for pastoral farming, the impacts of grazing and browsing animals, wind exposure and storm events.

Many of the surviving dendroglyphs stand in the Rotorua kōpi grove on Kaingaroa Station, on the north end of Rēkohu (Chatham Islands). It is a private reserve – fenced off to protect the remaining trees.

(The public can see rākau momori at the nearby JM Barker [Hāpūpū] reserve.)

Bare farmland surrounds the reserve, now a narrow strip buttressed by towering sand dunes.

The kōpi stand straight and tall, unlike the native akeake, which have bent and twisted in the island’s brutal maritime winds. Their dense canopy absorbs the gales, creating a cathedral-like silence in the groves.

They were once a living marae, home to entire communities. Kōpi (or karaka) were introduced to the island and cultivated for berries and kōpi nuts, which became a vital carbohydrate to the Moriori diet, much as kūmara was to Māori.

“This is one of the old living spaces,” says Moriori rangata matua (elder) Tom Lenauze. “People actually lived in here and up in the dunes up here. That's where the old people are, interned or where they are buried. It is a very sacred area to Moriori.”

The kopi groves provided shelter – and were in turn protected by the broadleaf forest that once surrounded it.

“It's used by modern day Moriori as an emblem of community because the canopy and the root system of the kōpi forest are all intermingled and rely on each other for support and shelter,” says Tony Blackett, chief executive of the Hokotehi Moriori Trust.

“On their own, they're quite exposed … they get smashed by salt-laden wind, which erodes the edges of the forest, they die back from the edge without the shelter of the broadleaf forest that was surrounding them, they're gradually corroding.

“Reforestation of the island is critical for the survival of the kōpi.”

The trust established Recloaking Rēkohu, a project to restore native forest to the island creating a reserve 13 years ago. Other measures include pest control, increasing soil fertility, and the planting of wind shelters. The trust employs two full-time biodiversity rangers.

“Within the Moriori community, there's a concept called T'chieki which is similar to kaitiaki-tanga within the Māori community, and that refers to guardianship or taking care of your place,” he says.

A 2010 study, by the Department of Conservation and Otago University, used laser scanning to assess the deterioration of the ancient carvings.

The following year, the trust began removing the dying trees for conservation.

They are treated and conserved at Kōpinga (meaning grove of kōpi) marae with a plan to eventually display them in a Whare Taonga [museum].

“When they start to die, the bark actually comes off the tree. And we lose the rākau momori.”

Twenty-three trees have been harvested to protect them. “They will be preserved for all time.”

Lenauze’s daughter Loretta Lenauze is t'chieki marae, guardian of the marae. While the historical loss of the rākau momori is heartbreaking, the trust is helping people to re-learn the lost art.

The carvings – which are actually bruisings that don’t penetrate the bark – feature stylised human images, fish, birds, seaweed, seals and crayfish.

It’s part of a revitalisation of the Moriori, who were almost wiped out and saw their land, culture and language vanish.

“The rākau momori are very significant to our people as part of our regeneration of Moriori people,” Loretta Lenauze says. “Acknowledging our surroundings is very important to us as Moriori.

“I'd probably describe it as ruggedly beautiful. It's quite harsh here. And we live in quite an open space, in a harsh environment. But actually, it's extremely warm in mauri [life force] and wairua [spirit]. Which is a huge part of us.

“I've seen photos of what it did look like, in the past…rolling native bush. We don't have much of that left now, of course, because people developed that land into farmlands or different properties and stripped them bare.

“It's really important that we take steps to preserve what we have, and also make things better. It's extremely important to have great ecosystems and to look after what we do have.”

Resurrecting the chiefs of the forest

When Māori arrived in New Zealand, the islands were almost completely shrouded in lush, dense forest.

In Māori mythology, the god Tāne Mahuta created both humans and forests, binding the two forever. They hold spiritual value, but also provided food, medicine and wood for fire and building.

As more people arrived, the forests were burned and cleared for settlements and farmland, and slow-growing natives were felled for building and fencing. Logging of native forest on public land continued into the 1980s.

Globally, forests are hanging by a thread, with a recent report revealing 30 per cent of the world’s nearly 60,000 tree species are at risk of extinction.

Between 1996 and 2018, New Zealand lost an estimated 44,800ha of indigenous forests, scrub and shrublands.

As well as deforestation, taonga species now face the threat of diseases like myrtle rust and kauri dieback.

Myrtle rust was first identified in 2017, and has quickly spread across the country, reaching Christchurch in May.

The disease spreads on the wind, ravaging 37 species in the myrtle family, including pōhutukawa, rātā and mānuka, and scientists have foreshadowed localised extinctions.

The microscopic fungus-like organism phytophthora agathidicida was discovered in a stand of kauri on Maungaroa Ridge, above Piha, in 2006, and the disease was formally identified two years later.

Humans and browsing animals spread contaminated soil. Delicate root systems succumb when trampled, or are weakened by drought.

“It's a devastating disease that is fatal to all kauri that are infected,” says Lisa Tolich, Auckland Council kauri dieback team manager. “And unfortunately, there's currently no cure.

“The pathogen infects the tree through its root system. It effectively starves the tree, stops the uptake of water and essential nutrients right up into the canopy.”

Much of the original kauri was cleared and what remains are mostly in fragmented remnants of ancient forests or in regenerating stands.

For more than 1000 years, Aunt Agatha has reached for the skies above Te Wao Nui a Tiriwa, the 16,000ha Great Forest of Tiriwa, which blankets the Waitākere Ranges.

Her column-like trunk still stands solidly, but the spreading crown is now naked of leaves, blanched skeleton-like branches stark against the green canopy.

“Unfortunately, Aunt Agatha now is dying. Kauri take a long time to grow and a long time to live. They also die slowly. This rangatira has fallen,” says Edward Ashby, of local iwi Te Kawerau ā Maki.

“It is heartbreaking for us, for our ngahere [forest]. That's a real testament to how awful we've been doing a job of looking after the place.

“If your biggest, strongest, tallest member of the forest family is sick, that sends a very strong message that something's not right, and that you have to do something about it.”

In 2017, at the foot of Aunt Agatha, Te Kawerau ā Maki called down a rahui (customary prohibition or closure) on the forest.

Ashby says it’s “our strongest indigenous conservation management system”.

“Five hundred years ago, you wouldn’t have come into a rahui, based on fear of death. We have to adapt with the times of course, but it's still a very strong measure. The focus is on healing the life force of the ecosystem.”

Te Kawerau works with scientists from Auckland Council, Landcare Research, Scion and the Ministry for Primary Industries to stop the spread.

Since July 2018, a Natural Environment Targeted Rate was included in residential property rates across the city and is expected to raise $311 million over 10 years. More than $100m was ringfenced to manage kauri dieback and myrtle rust.

Tolich leads the targeted rate-funded programme. It includes pest management, monitoring and surveillance and research into treatments.

There are also innovations such as a trial to train kauri dieback detector dogs, jagdterrier Marwhai, and english springer spaniel Pip. They’ll be deployed to sniff out the fungus on footwear, vehicles and equipment.

And there have been trials with phosphite, a fungicide used in horticulture.

Tolich says this is a “holding pattern”.

“Those trials are being scaled up. That is slowing down the progression of the disease. But it's not a cure.

“I always remain hopeful science is going to catch up to these precautionary measures we're putting in place. That's all about buying time.”

Te Kawerau and Auckland Council will also slowly reopen the tracks.

In February, trampers were welcomed back onto the Ōmanawanui Track and Puriri Ridge Track, on the Hillary Trail, which were carefully upgraded with specially-mixed gravel, thousands of steps, and hundreds of metres of boardwalk.

The Department of Conservation also installed cleaning stations on tracks for boots and other hiking gear.

“We needed to make the tracks safe in terms of not spreading soil, and also build them in a way that allows the kauri root systems, damaged by foot traffic, to heal,” says Stu Leighton, an Auckland Council park ranger, who has patrolled the forest for 20 years.

“More and more people were walking this track, because it is stunning. But they didn’t want to walk where it was really muddy and slippery, choosing to go wider, so the footprint of damage was getting bigger and bigger.”

By building boardwalks, trampers were lifted from the ground.

“We'd hope to see root system repair, the leaf litter building back up. Because the healthier the forest is, the more it is able to withstand the impacts of climate change and droughts, browsing animals, or pathogens like kauri dieback.”

Tolich says kauri are a “keystone species” for the forests they inhabit.

“When we talk about kauri, we tend to talk about an entire ecosystem, because that's what they support. There's at least 19 different species that are dependent on kauri.

“We're talking about the loss of an entire ecosystem. And that's really concerning for a lot of ecologists.”

She fears we may lose kauri altogether, killing off a species that once towered above dinosaurs.

“We have less than four per cent of mature kauri left. They used to cover a lot more of our landscape. Because of forest fragmentation and impact of people over time, that has reduced considerably.”

Fossil evidence suggests they once grew as far south as Invercargill, but now only exist north of Kawhia.

“New Zealand has a lot to thank kauri for,” Tolich says. “A lot of the foundations of this country were built on kauri. They've built cities like San Francisco, Melbourne, Sydney, the gum industry and timber industry. There's a lot that we need to do to protect what we've got left.”

Not everyone has joined the fight. Some West Auckland residents opposed the closure of the tracks, and have questioned the authority of the rahui.

Some have also ignored track closure signs. And earlier this year rogue tramper Robert Armitstead was fined $5700 for repeatedly breaching the prohibition bylaws.

Ashby has no truck with the critics.

“Our old people say the environment knows how to heal itself if you just get people out of the way.

“Kawerau have, for the last 150 plus years, had to watch others come in and trash our whare, our house. Come in with their dirty boots, chop down our ngahere, burn it.

“We're responding because we're responsible kaitiaki. [I] don't care if I never get to walk in this ngahere. So be it. As long as it's here for tomorrow and for the generations that follow. That's what's important.

“So that's my response to people that critique. Critique all you like, the kauri will still stand when you're long gone.”

A re-emerging threat

Like disease, pests do not respect our human boundaries.

Deer were first brought to New Zealand in the late 19th century for sport, and by the 1960s the populations were out of control.

Government culling and commercial hunting dramatically reduced numbers, but in recent years has failed to keep pace with breeding rates.

“Deer are building up to levels where they haven't been seen since the 1960s, the 1970s,” says David Carlton, who leads a biodiversity threats project for the Department of Conservation.

They are no longer confined to the back country, moving into areas where they have never been seen or were absent for a very long time.

“Now they’ve come out into our rural landscapes and are living in pockets of bush and lowland reserves, using these bits of bush for cover and coming out and eating all the neighbour's crops,” he says.

“These deer are healthy, they're getting big and fat, and they're breeding up. In places where you might have previously only seen one or two, you might now see a couple of hundred deer.”

For Sir Alan Mark, Emeritus Professor at Otago University’s Department Of Botany, their return threatens entire forests.

Mark led a vegetation study in Mount Aspiring Park in the late 1960s that laid bare the damage done by herds of deer invaders.

As well as trampling delicate roots, ferns and mosses that had evolved in the absence of hooves, they stripped bare every branch within reach. And when the forest cover thins, the soil becomes prone to erosion.

“Deer are not natural in New Zealand, we don't have any natural land mammals. And they really did get out of hand, particularly in the remote areas,” he says.

“They're very selective in what they eat. So if the forest is totally occupied by deer they can remove species one-by-one as they choose the most palatable remaining plants.”

His photographic survey – which continued until 2007 – coincided with the commercial hunting boom, and he was able to chart the regeneration of the forest.

“The results were nothing short of spectacular. The forest went from bare to a situation where you couldn't really show the marker stakes because the growth of the beech regeneration was just so continuous.“If the deer had persisted in the numbers they were at that time, eventually the dominant trees would be affected. Mountain beech has about 200 years lifespan. And when it's overmature and collapses with a snowstorm or a windstorm, there may be nothing, no other beech seedlings there to replace it.

“The forest is actually threatened if the animal numbers are large, and persist indefinitely. The security of the forest might be at stake.”

Carlton says the deer recovery industry has “gone through peaks and troughs and at the moment it is in a real lull”. And recreational hunting is not enough to keep on top of the breeding each year.

Monitoring shows numbers increased by 34 per cent in the North Island and 21 per cent in the South Island in the last six years, he says.

A national cull would be expensive, and likely ineffective. DOC was recently stung by a proposed tahr management plan which was challenged in court.

Now Cartlon is working with iwi, conservation groups and hunters to design a plan to manage wild deer.

It is currently focused on the North Island, in the Raukumara Ranges, the Kaweka and Kaimanawa ranges, and the Ruahine Range.

“When you start to shoot deer in a population that is of a reasonable sort of size, the first lot that you take are going to be pretty easy. So it's relatively cheap.

“When you get down to only a few left, but you haven't got it down to the level where you're going to get that recovery of the forest, those deer are really expensive.

“So it's a tricky one. It would take millions of dollars to do a reasonable sized area, to keep them at a level where the forest will bounce back. It is a significant cost involved.”

Ashby says we devote too few resources to protecting our forests.

“Our forests are … nationally significant infrastructure. We'll spend $600 million on a road so we can move trucks full of potato chips from Auckland to Whangarei, but we put a million dollars, if we're lucky, into our forest.

“These are the things that will help us be more resilient to climate change, the biodiversity nets … they are the lungs of our city.

“If we don't look after something as critical as essentially the thing that cloaks the earth, and life, and we give it less than one per cent of what we do to a motorway, what does that say about us? The conversation has got to change.”