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World Oceans Day is on the 8th of June. Since 1992, the United Nations has taken this day to celebrate all the ways that the ocean supports our lives and livelihoods, and to highlight the significant challenges we face in ocean conservation.

To mark this event, and key international climate change talks later this year, our marine team is bringing you a series of blogs to celebrate the vast big blue that surrounds us, while learning more about its role in climate change mitigation and adaptation. 

By Irene Llabres Pohl, Technical Advisor Mountains to Sea; and Helen Kettles, Technical Advisor Marine Ecosystems

Okarito Lagoon. Ship Creek with mountains in background, South Westland.
📸: Andris Apse

With fundamental changes being observed throughout New Zealand’s and the world’s oceans (see previous blogs), it is pressing for us to better understand and devise strategies to safeguard the health of the ocean on which human well being depends.

Climate change impacts are often tricky to disentangle from the many other pressures we put on the environment, let alone manage. But we must try! We’re working to future-proof all the work DOC does in the marine space, in line with our Climate Change Adaptation Action Plan. The ocean does provide us with some phenomenal opportunities to put us in a better position to face climate change. Here a few sure-win action:

Nature-based solutions

Unsurprisingly, nature knows best and will have the best chances to adapt if we leave it be. So called nature-based solutions involve working with nature through protection and restoration to maintain or re-establish natural resilience to cope with change. Because nature-based solutions are about working with nature to manage climate change impacts, they simultaneously provide other benefits such as biodiversity protection. In light of the ongoing biodiversity loss crisis, nature-based solutions are our best allies.

What are some of these solutions?

Marine protected areas

Marine protected areas (MPAs) can work to restore and  protect the natural functioning of marine ecosystems and with it the many ways us humans benefit from it (food, medicine, and wellbeing) by limiting extractive uses. While they cannot stop external pressures such as pollution, we manage those through other tools, they provide species, habitats and ecosystems with a safe haven from direct impacts. The thinking is that by protecting marine ecosystems they will be healthier and more resilient to climate change impacts.

Marine reserves provide the highest level of protection in New Zealand but other tools at our disposal include fisheries closures and customary management approaches. Learn more about the marine reserves DOC manages.

Jewel anemone in Poor Knights marine reserve
📸: Vincent Zintzen

Restoration and protection of coastal ecosystems

Coastal ecosystems including estuaries are at major threat from climate change due to sea-level rise, marine heat waves, and extreme weather events. They are also amongst some of our most degraded ecosystems, which limits their capacity to act as floodwater protection, water filters and fish nurseries. In light of climate change, protecting and restoring coastal ecosystems such as seagrass meadows, saltmarsh (a shout out to all the community groups actively doing this), and shellfish beds (another shout out to the great people at Revive our Gulf), is key towards building coastal resilience.

DOC working with communities to restore Cobden Aromahana Sanctuary, Greymouth
📸: Henk Steng, DOC

Blue carbon

Blue carbon is the carbon stored naturally by coastal and marine ecosystems. Simply put, carbon taken out of the atmosphere means less green-house effect. Coastal ecosystems such as seagrass, mangroves and saltmarshes are, though relatively small in extent, true blue carbon superstars, representing about 50% of the marine carbon sink. Mangroves for example can store up to 10 times as much carbon as the same area of land-based forests. This is because they don’t stop storing carbon when they reach their full height like trees do. Most of the carbon is sucked down by these plants and locked up in the sediment and that can process can go on forever.

When these ecosystems are degraded not only do they stop taking carbon out of the atmosphere, they will also release carbon back into the atmosphere when they decompose. Protecting and restoring these natural carbon sinks are recognised as an important component of climate change mitigation.

Kelp forsts, such as this in Ulva Island-Te Wharawhara marine reserve, take CO2 out the atmosphere to grow.
📸: Vincent Zintzen

Cushioning the effects of ocean acidification

CO2 released from fossil fuels is being absorbed into the oceans and causes ocean acidification which impacts a variety of animals with shells (see Blog No. 2).

But nature even has some solutions for this!

As marine plants grow they are sucking the CO2 out the water (just like trees do from the air). It’s a lesson in chemistry  – in doing this they are reducing the acidity of the water around them. So, at marine reserves like the ones at Leigh, where protection has allowed kelp forests to recover they are banking blue carbon AND reducing the acidification impacts on nearby species. Kelp and seagrass associated with mussel farms will also provide some protection to this export industry. Isn’t nature amazing…the gift that keeps giving.

Seagrass at Pauatahanui inlet
📸: Wriggle Coastal Management

Practical adaptation action

Marine species are already vulnerable to a range of threats and climate change poses an additional risk. For example, over the last couple of years DOC has recorded highest ever pup mortality of New Zealand sea lion/rāpoka/whakahao on Campbell Island, the breeding site which accounts for 30% of pups born into the population. More research into this is needed but currently we think that the changing climate might exacerbate the already harsh environment, favouring conditions such as heavy rainfall and subfreezing temperatures at a time when pups are at their most vulnerable. To help sea lion pups adapt DOC is currently trialling different designs for pup shelters at various fur seal colonies around the mainland. This is a joint project with Auckland Zoo and landowners. 

Seal pups going for a mud bath on Campbell Island
📸: Dahlia Foo

Environmental health disclaimer

The above information might raise the illusion that we can get ourselves out of severely cutting down greenhouse gas emissions because marine ecosystems (like forests on land) suck CO2 out of the atmosphere and we have some idea about how to help nature adapt to climate change. As an unprecedented global challenge, there’s still much to learn (not that climate change is happening, we’re way past that) but one thing we are clear is that the severity of the challenge ahead is set by actions we take now. Cutting down emissions from fossil fuels and agriculture (because methane is 80 times more effective in trapping heat as CO2) still needs to be a primary focus. But we need all the help we can get so it’s get onboard with nature too as it’s so worth it!

Find out about the government’s Carbon Neutral Government Programme.

For more information about climate change and conservation, visit our website:

With the launch of the Predator Free 2050 strategy: ‘Towards a Predator Free New Zealand’, we’re doing a series of blogs about the pathways identified in the strategy which are going to help us get to Predator Free.

One of those pathways is toitū te mahi haepapa kīrearea – moving from sustained predator control to eradication. We look at the work of ZIP to remove predators and protect our special places.

The current predator control approach on mainland New Zealand is the suppression of predator populations using traps or toxins. Ongoing suppression always carries the risk of reinvasion and must be continually managed. 

New Zealand is a world leader in removing invasive predators from islands and predator fenced areas but creating mainland safe havens has historically relied on relatively small scale fenced sanctuaries to keep out invasive predators.


Enter Zero Invasive Predators Ltd (ZIP), a research and development entity, who are leading the way to remove possums, rats, and stoats from large mainland areas.

ZIP was established to develop operationally ready and innovative technologies that will help us create large areas free of possums, rats and stoats, and protect them from re-invasion. They call this model ‘Remove and Protect’.

A ZIP field ranger searches for a radio signal, Perth River valley. 📷: Chad Cottle

The Remove and Protect approach, if successful, will make it possible to:

• Carry out predator control in terrain where it is neither desirable nor possible to construct predator fences

• Reduce our dependence on the repeated wide scale application of toxins at chosen sites

• Enable progressive expansion of a protected area as funds and confidence allow

• Create an environment on the mainland where, in time, ecological integrity could rival that of predator-free offshore islands

The Remove and Protect approach is probably best suited to land areas bounded by geographic ‘barriers’ such as oceans, large rivers and alpine tops, making them relatively easy to defend once predators have been removed.

South Westland’s Perth Valley

ZIP, supported by DOC, Predator Free 2050 Limited and the NEXT Foundation, is currently developing the Remove and Protect approach in the 10,000 ha Perth Valley, South Westland. Last year they carried out an initial predator removal operation, using a modified application of aerial 1080, which succeeded in removing all stoats, and all but a very small number of individual possums and rats.

The Perth River Valley and Great Unknown beyond, hidden behind cloud. 📷: Chad Cottle

The challenge now for the ZIP team is to remove the remaining possums and rats before they re-establish within the valley, and then to protect the valley against reinvasion from outside.

The Perth River valley is surrounded by cold, fast-flowing rivers, and by Kā Tiritiri o te Moana (the Southern Alps). Previous research by ZIP suggests that these rivers will be strong barriers to reinvasion by both possums and rats (reinforced in places by kea-safe traps).

Some level of reinvasion is expected, and ZIP is using a highly sensitive network of lured cameras throughout the field site to alert the team to any predators that get in, so that they can quickly respond. ZIP is making exciting progress toward permanently protecting this spectacular place from the adverse impacts of possums, rats, and stoats – great news for our endangered native species!

Towards a Predator Free New Zealand

A future Aotearoa, flourishing with abundant native wildlife and forests is the bold vision that has galvanized thousands of New Zealanders into active support for a predator free New Zealand by 2050.

The Predator Free 2050 strategy, ‘Towards a Predator Free New Zealand’, sets out a framework over the next 30 years for New Zealand to address the current biodiversity crisis and achieve the predator free goal.

Find out more about ZIP:
Find our more about the Next Foundation:
Find out more about Predator Free 2050 Limited:

Here’s how things are looking right now for mohua/yellowhead; and why conservation will continue to require a lot of ingenuity and quick thinking, in advance of meeting our Predator Free 2050 goal.

Which makes for some weird and wonderful work stories …

By the Department of Conservation

Mohua / yellowhead bird on Anchor Island
📷: Leon Berard –

We’re worried about mohua—not just mohua, but definitely mohua—as these tiny kowhai/yellow creatures are currently embroiled in a battle for survival they’re too small, too bright, too loud and too smelly to win on their own.

(More on smells soon).

For a long time we’ve been working to protect the mohua population from predators by means of moving birds to create new colonies, and doing extensive predator control at the most important sites on the mainland.

Recently, we had our Predator Free Manager Brent Beaven on the DOC Sounds of Science podcast to talk about our goal of ridding Aotearoa of rats, stoats and possums by 2050.

Brent has several decades of hands-on conservation experience.

And sometimes feet on, too.

We’ll let him explain that.

Audio extract from the DOC Sounds of Science Podcast

Transcript of the above clip:

Brent: “I was catching mohua—or yellowhead—on the island, and we’d struggled for days. And we’d only had 15 birds. And you normally want 30 to 50 to try to start a population … and we’re 15 minutes to go till we called it quits and the helicopter arrived.

“I caught 30 mohua in one go. So they’re in the net and they’re everywhere. The only problem was, I didn’t expect that. And there was only me. And I didn’t have enough catch bags.

“So I took my socks off. And I stuffed some mohua in my socks. And I tied my sleeves up on my raincoat and put mohua in the raincoat. Every little pocket, and everything I could do, I had filled with mohua.”

Brent Beaven

To get to the point where mohua need to be in Brent’s socks to be safe is …. alarming.

But it is at that stage.

New Zealand has one of the worst extinction records of any nation and, today, some 4,000 native species are considered to be at some kind of risk. Around a quarter of those are in real danger of extinction. Mohua are in this mix.

Mohua were once widespread across the whole of the South Island, but have been radically reduced to a few fragmented and sparse populations since humans arrived — and even these are still declining.

Overall, the mohua population (currently estimated at 5000-20,000) has declined on the mainland in the last 150 years and there are concerns this trend will continue without further intervention.

The evolution

As most Conservation Blog readers will know, native species in Aotearoa evolved in the absence of most mammals. The only mammals that are from here are seals, sea lions, and bats, none of which present a problem to our endemic bird populations.

When predators like rats, stoats and possums were introduced, our problems began.

Mammalian predators like these ones hunt by tīare/scent, sound and sight. They sniff out and track down the things they want to eat. Like mohua, hence we opened this blog by calling them loud and smelly. It wasn’t to be mean, more to point out the odds are stacked against them.

Most stoat predation occurs when the chicks are large and vocal: a stoat can hear them begging for miles around a nest, which acts as a large summoning bell for predators.

(Interestingly, mohua don’t smell quite as distinctive as kākāpō, who are known for their particularly floral pong. The distinct scent of kākāpō birds and nests has been likened to potpourri, or the inside of a violin case, or a bunch of very strong roses).

Checking a mohua nest in the Catlins
📷: DOC

For both kākāpō and mohua, their habits make them easy pickings—kākāpō nest on the ground, and mohua nest and roost each night in tree holes.

Our birds, having evolved without land-based mammalian predators, were used to looking out and up for ruru and Haast’s eagle and the like. Their defence was to stay still and quiet and wait for the predator to keep flying.

It’s also why our native species are fauna coloured – no neon parakeet pinks or mcaw reds for our birds. We stick to the blues of water, the yellows of flowers and greens of the ngahere.

Our birds need to blend.

But blending is no good when you smell, and when you’re loud, and you nest in very easy-to-reach places.

We’ve lost too many of our native species in the last 800 years.

So we’re in a bind.

A big, bird bind.

We could do a deep dive on all of our Threatened and At Risk species, but today it’s mohua.

Close up of kākāpō feathers showing their distinct kākāriki/green foliage colours
📷: Sabine Bernert

How are mohua doing, you ask? Not great

Mohua are a taonga for Ngāi Tahu. They’re sparrow-sized, yellow-headed birds found only in the South Island in native forest.

Mohua were once widespread, found all over the beech forests of the South Island. But by the mid-1990s the population was in Very Serious Trouble. By this time, mohua had disappeared from more than 90% of the South Island. In places like the Landsborough Valley, there were just over a dozen left.

Mohua were looking extinction in the face.

Through intensive predator control, the decline in the Landsborough Valley was reversed.

But we’re a long way from home safe for mohua.

Our predator control has not been intensive enough at most of the other core sites.

Because mohua are extremely sensitive to predators, they’re often an indicator species for how successful predator control is in an area. If you see lots of mohua, things are going great.

But we’re not seeing that in many places.

Mohua / yellowhead bird on Anchor Island
📷: Leon Berard –

Mohua are responding well to predator control in the Landsborough in South Westland and Hurunui South Branch in Canterbury, but are currently declining at other key sites such as the Catlins, Blue Mountains and Dart and Eglinton valleys.

We know for a fact that aerial 1080 saves species, and we wouldn’t have a hope of keeping anything alive without it. We’re on the lookout for a better tool, but until then, 1080 is the only large-scale option we have.

For mohua, just like all endangered native species, the period between mast and 1080 application is critical and requires extensive complementary trapping networks to keep stoat numbers down.

Let’s walk through this:

In Landsborough and Hurunui South Branch, where there’s 1080 use as well as extensive trapping networks to keep predator number under control in between mast times, mohua are having a ball*

(*Well, close. They’re slowly increasing, but compared to rapidly decreasing, that’s a ball).

However, at sites such as the Catlins, Blue Mountains and Dart and Eglinton valleys, they’re still declining. The reasons behind this are complex but it’s to do with masts.

The predator plague cycle as influenced by forest mast
📷: DOC

A mast is when more flowering trees leads to more seed, leads to more predators, leads to more predation. (Here’s an animated short showing how this works). It doesn’t happen every year, but when it does, there’s an explosion in predator numbers.

There are a few reasons for mohua to be struggling in some sites, despite our best efforts.

Monitoring shows that using aerial 1080 to control beech mast predator plagues is more effective in silver beech forest than in red beech, which produces more seed.

And predator control regimes relying on aerial 1080 without extensive complementary trapping networks to keep stoats down between forest masts also seem less effective for mohua.

Climate change plays a factor too, as the increasing frequency in forest masts means species like mohua have less time to recover between masts, because more rats naturally survive the winter.

The Mohua Recovery Group, which includes Department of Conservation and Ngāi Tahu representatives, is looking at options to improve management at these sites to try and turn this trend around.

And it’s fair to say that conservationists and Predator Free experts, like Brent, are busting a gut trying to do their best for mohua.

There are also mohua populations which appear to be stable on the eight pest-free offshore islands in Fiordland and Southland, where additional populations (estimated at 3000 birds) have been successfully established.

But these populations are reliant on everybody undertaking good island biosecurity. Pest incursions to these islands would be costly and deadly for precious species.

This is all to say: mohua aren’t yet in the green, despite improvement at some sites.

Mohua in hand
📷: Colin O’Donnell DOC

So what?

This is why Brent’s story about catching mohua in his socks was a laugh-then cry moment.

One of those ‘oof that’s funny but dire’ situations.

Someone catching birds in their socks and popping them in pockets is funny.

The fact they’re doing it because the species is in dire straits and will die out unless we can get enough birds to translocate them to offshore islands, which is currently the only way we can be confident about their survival is not so funny.

Brent told us the mohua-sock story recently and we published it on the podcast last week, but the actual sock-catching happened years ago. This was on Breaksea Island to get enough birds to successfully establish a population on Whenua Hou.

It worked.

Brent’s socks weren’t an elegant solution, but they were a solution. 

The mohua population on Whenua Hou is doing pretty well, because it’s a predator free island.

If we can meet our ambitious goal of making all of Aotearoa Predator Free by 2050, our mohua could become a frequent sight on our main islands.

Imagine mohua all around Te Waipounamu/the South Island!

That would be neat.

To hear Brent explain the PF2050 goal and lay out the key mahi, have a listen to the DOC Sounds of Science Podcast, available wherever you get your podcasts. Part 2 of our chat with Brent will be out next week.

Episode 13: Predator Free and me (part one) DOC Sounds of Science Podcast

Brent Beaven tells us everything we need to know about New Zealand's goal to be Predator Free by 2050. How will we? What is this? Is it even possible? Brent has the answers. In fact he has so many, we’ve split his interview in two. Brent is an expert on predator control and has decades of hands-on field experience. He's herded sea lions, been hounded by kiwi, and caught mohua in his socks. In the world of threatened species conservation, you name it and Brent has done it. Listen and learn. Show notes available at

For more about mohua see: