environment

$30.5 million hit planned for ‘mega mast’

Poison drops over a million hectares are planned to counter a 'mega mast' predicted to spark a plague of predators in native forests. David Williams reports.

When I last visited a forest frequented by orange-fronted parakeet/kākāriki karaka, there was quiet optimism.

In 2009, I accompanied Department of Conservation (DOC) ranger Sandy Yong to Canterbury’s Hawdon Valley, near Arthur’s Pass, while she checked rat tracking tunnels and traps. Back then, kākāriki numbers were estimated to be between 200 and 400 birds in three valleys – the Hawdon and Poulter in Arthur’s Pass National Park, and the south branch of the Hurunui River. Yong thought the bird numbers were slowly growing. But she was concerned about a predator population explosion from that year’s beech mast.

Today, kākāriki are holding on, but only just.

DOC senior ranger Lyndon Slater says there are only 100 to 150 birds left. Most are in the Hurunui, with about a dozen birds in the Poulter and “virtually nothing” in the Hawdon. Over the past year, DOC has intensified, improved and extended its trap network, planned a ground poison operation and is installing live capture cat traps.

There’s an “insurance policy” – a captive breeding programme combined with transferring birds to predator-free islands. The question is, will it be enough? The signs are that the country’s forests will be bulging with critter food next year in a so-called mega mast.

“If we were solely reliant on our wild population, I’d be really nervous coming into this mast,” Slater says.

Beware the mega mast

A mast year is one in which trees produce high amounts of seed that drop to the ground and are gobbled by predators, like rats and stoats – as well as native species, of course, including forest-dwelling insects. (In non-mast years, beech trees will often produce no seeds or very few.)

There’s no formal definition of a mega mast.

Nelson-based DOC scientist Graeme Elliott says it’s when heavy seed falls are expected pretty much everywhere, in all the beech forests. (He points out, however, that it doesn’t take a heavy beech seedfall to cause a mice and rat plagues. “The heaviness of the seedfall isn’t so important as the widespreadness.”)

He reels off the places like eastern Fiordland, Te Anau, Eglinton, Landsborough, Arthur’s Pass and Kahurangi, where it’s flowering prolifically. “The Tararuas, for example, they’ve kind of gone ape-shit.” It’s far from a complete picture, he says. “But everywhere we’ve heard back from suggests it’s going to be a biggie.”

(According to online encyclopaedia Te Ara, beech trees are found in between 80 and 90 percent of South Island native forest, but only 40 percent in the North Island.) 

Forest & Bird chief conservation adviser Kevin Hackwell says while the beech flowering is significant, what’s really concerning about this coming year is that many podocarps – rimu, kahikatea, miro – will be fruiting as well.

“So it’s a double whammy,” he says. “That is going to put a huge amount of pressure on our forests and our wildlife – no question.”

Two hundred years ago, mast years would have been bumper times for native species. But because mast years can cause plagues of mice and rats, and stoat irruptions, there are fears that without some intervention some struggling species will be wiped out in some areas, becoming locally extinct.

Conservation Minister Eugenie Sage confirms $30.47 million has been set aside for the 2019 mast response, over two financial years. That intervention will come mainly in the form of aerial 1080 poison drops. The area covered by the drops is expected to be about a million hectares. (The poison is also used to stop the spread of bovine tuberculosis.)

A beech tree flowering in Fiordland in 2013. Photo: DOC

Mast years can be predicted.

With podocarps, like rimu, the evidence is easy to see. Elliott: “We just climb up the trees and see the seeds. We can predict rimu coming a year in advance.”

For beech trees, mast predictions have been helped by the “delta T” model developed by University of Canterbury’s Dave Kelly and several colleagues in 2013. It’s based on the difference between average summer temperatures in successive years. Basically if the second summer is warmer, on average, than the last, there’s a high likelihood of a mast in the coming year.

Last summer was two degrees warmer than the summer before, Elliott says. “It was the biggest difference between two summers that we’ve had for a long time. It’s the strongest signal.”

With decent masts in 2014, 2016 and, soon, 2019, that’s a little more frequent than the long-term average, of two-to-six years for beech trees. Is that climate change? Elliott says he’s no climate scientist but it might just be bad luck. Hackwell, on the other hand, says the constant increase in global temperatures will mean more frequent mast events. (He also worries about the stress on the trees themselves.)

There’s also physical evidence of the mast. Beech trees have turned red with flowering, with some hillsides exhibiting an orange blur – starting low and moving up the hill with the temperature. Clouds of pollen have filled the air.

(Sage is keeping a close eye. “I’ve already seen tī kōuka/cabbage trees in Canterbury laden with flowers; harakeke/flax shelter belts in Southland with heavy flowering, and reports of heavy beech flowering on the West Coast.”)

In February, DOC does aerial checks to see if the flowers have turned into seeds, which will then ripen. Increased seed will also show up in rat and mice tracking, as numbers rise with more food available.

Hackwell says while it won’t be known till late autumn how big the mast is going to be, a cool summer can alter its trajectory. But all other things being equal, he says, “it does look really bad”.

“We won’t be able to treat, this year, all the forests that are masting.” – Graeme Elliott

Clues to the big mast first appeared in March, so DOC has had plenty of time to plan.

Elliott: “We have a committee that makes a decision about prioritising sites. When you have a big mast year on then you’ll devote most of your effort to places that have mast-sensitive species – that’s species that are particularly sensitive to rats and stoats.”

Those species include mohua, orange-fronted parakeets, rock wrens and short- and long-tailed bats. Or as Elliott puts it, “stuff that might go extinct”. “They can take a real pasting from rats and stoats – and not only kill their babies but they can kill the adults as well.”

Below the top priorities are species like kiwis, kea, kākā, and whio, whose nests might be lost – to stoats, mainly – and a few adults might be killed, but it won’t be catastrophic.

(Beyond birds, Elliott says big land snails, powelliphanta, “take an absolute pasting” but are unlikely to go locally extinct.)

But DOC’s planning for poison drops isn’t easy. There are capacity issues with the number of available helicopters, 1080 bait factory production, and finding enough people experienced in running such operations. Some forests are more expensive than others, depending on whether they can drive a truck to the operation area.

“We won’t be able to treat, this year, all the forests that are masting,” Elliott says. “So there’s a prioritisation exercise. We’re still planning and budgeting.”

DOC prioritises well, Hackwell says. And Forest & Bird was pleased to see extra money for pest control in the Budget. But in a mega mast, a million hectares doesn’t cut it, he says. “The reality is that we actually do need more.”

Hackwell reckons between five and six million hectares of forest might need of pest control in a mast year. Add to that climate change is likely to increase the frequency of rat and stoat plagues, he says more money will be needed to handle them.

“We’re talking to the Government and to DOC about our concerns.”

Colourful beech trees in the Rees Valley, Otago, in November. Photo: Richard Hursthouse

In a narrative-interrupting diversion, a mast year isn’t all bad. It’s expected to be a boon for one of the country’s beloved parrots, the kākāpō.

Codfish Island/Whenua Hou, about three kilometres north-west of Stewart Island/Rakiura, and Anchor Island/Puke Nui, in Fiordland’s Dusky Sound, are home to New Zealand’s main populations of kākāpō. (The third is Te Hauturu-o-Toi/Little Barrier Island, in the Hauraki Gulf.)

Kākāpō and takahē expert Andrew Digby, a DOC scientist, says both islands have really high amounts of rimu fruit. “It’s the biggest rimu mast that we’ve ever recorded. So we’re expecting the biggest kākāpō breeding season that we’ve had on record in recent years.”

DOC counts fruit on rimu trees. If more than about eight percent of the tips of the rimu have new fruit developing then normally the kākāpō breed. In March, the count on Whenua Hou was 47 percent. That has dropped to 40 percent – but that’s still above the previous record of 38 percent.

“What it means is pretty much every female kākāpō will breed on those islands – every female of breeding age,” Digby says.

That’ll be a much needed boost.

There are 148 kākāpō and the population is slowly increasing. But the likeable parrots face lots of problems. The biggest is infertility. “Only about half of the eggs hatch,” Digby says. “And only about a third of the eggs that are laid turn into chicks that fledge.”

Last year, for example, there were 122 eggs laid but only 34 chicks fledged. That’s a lot of lost potential, Digby grumbles. (The cause of infertility is unknown, he says – “but we strongly suspect, and there’s some evidence, that it’s genetic. So inbreeding is responsible for that.”)

That makes mast years like next year of huge importance. Digby: “It’s going to be a big one for us.”

1080 ‘essential’

Aerial 1080 drops have reasonably broad political support. (Coalition partner NZ First is an exception, with leader Winston Peters saying before last year’s election that it wanted to stop 1080 being used – although there’s little sign of that promise being kept.)

In May’s Budget, the Government announced an extra $81 million for predator control over four years. The idea was that instead of making DOC ask the Government for emergency funding in a mast year, that money would be part of DOC’s baseline budget. Before May’s announcement, DOC had just $6.4 million in its budget for pest control operations.

Conservation Minister Sage says: “Landscape scale aerial predator control using 1080 is essential to protecting threatened species at priority sites.”

While the National Party was in power, DOC invested tens of millions of dollars in increased predator control, over a vast area, under the ‘Battle for our Birds’ banner. Naitonal’s conservation spokeswoman Sarah Dowie says: “National welcomes DOC’s plans to build on our ‘Battle for our Birds’ record. We invested significantly in helping protect our bird species from devastation due to increased predator population in mast years.” (Dowie then parrots a line about strong growth in endangered bird numbers, that appears, word-for-word, in this story.)

Yet 1080 continues to be controversial, as shown by a series of recent public protests, and a heated court challenge to a proposed drop in Auckland’s Hunua Ranges.

Threats, some criminal, have been made against DOC staff. There’s even an academic battle on the sidelines, with Victoria University of Wellington’s Wayne Linklater basically accusing some scientists of abandoning facts in favour of values-based moralising.

Bill Wallace, of Golden Bay, a mussel-farming pioneer, former teacher and helicopter pilot, founded the Ban 1080 Party in 2014. In an interview with Newsroom, Wallace, who has an ecology degree, launches into a blistering offensive against DOC’s data, the interpretation of it, scientist’s research methods, the justification for poison drops and the claimed benefits.

“The more you read the more you realise this whole thing is an absolute crock of shite,” he says. “They manipulate, and they falsify, and it is pure propaganda.”

DOC doesn’t know what it’s doing, he maintains. “I believe they’re in an institutionalised state of atychiphobia, which is the fear of being wrong.”

An expert disagrees

Elliott, who has a PhD in zoology and has been working on conservation science for more than 30 years, says there might sensible arguments to be had about the morality of spreading poison in forests or whether it’s acceptable to kill deer. But he has no doubts about the science.

He says there’s incontrovertible evidence that mast years cause plagues of predators, and that those plagues threaten, and often kill, large numbers of species that DOC is trying to protect, particularly while they’re nesting. There’s also firm evidence to say that, with careful use, and in spite of the death of some native birds, like kea, 1080 is better for our birds, overall.

That view has high-powered backing from the 2011 report by then Parliamentary Commissioner for the Environment Jan Wright. She said: “While I respect the sincerity of those who oppose the use of 1080, without it our ability to protect many of our native plants and animals would be lost.”

(Also, DOC’s chaotic management of some bird species, its lackadaisical follow-up to some predator control operations, and its managers’ apparent adamantine aversion to “bad news” should not be confused with bad science.)

Elliott wrote his doctoral thesis on mohua/yellowhead in the Eglinton Valley, near Te Anau, in the 1980s. At the time, Elliott says, it was thought New Zealand plants and animals had declined to a point where they’d reached a new equilibrium; that everything was going to be fine. But his work, and that of others on species like kōkako and whio, found the opposite – that “they’re all about to disappear”.

Elliott spent about three or four years in the Eglinton. “And then we had one shit year when there was a big rat and stoat plague and they just got decimated. These were all my kind of pet birds and half of them got munched.”

He urges opponents of 1080 to think how many South Island kōkako, bush wren, mohua, saddlebacks and short-tailed bats were in Kahurangi National Park before it was poisoned for the first time. “There’s a whole lot of species that aren’t there. And I just don’t know why somebody – I suspect they really don’t know their birds – would say it’s good [before widespread pest control]. All this stuff is gone.

“We’re barely hanging onto what’s left and, in fact, I think there’s good evidence that things like whio and kiwi and kākā almost disappeared from places like Kahurangi and they’re just making a little bit of a comeback at the moment because it’s had reasonable pest control for the last few years.”

One wonders what would have happened to Canterbury’s kākāriki without intensive pest control.

Over the past 10 years, an area of about 30,000ha of kākāriki habitat has been regularly dosed with 1080. Next year, there’s an aerial operation over close to 100,000ha, primarily to protect kiwi. DOC ranger Slater says: “And our Poulter site falls bang within the middle of that.”

The bird’s sensitive to almost everything. The wild population is so low it’s now facing competition from other native birds. The captive birds are striking a genetic bottleneck.

Slater: “We’ve hit pretty much every roadblock and we’ve also been throwing virtually every [pest control] tool at the birds that we can.”

In years like the last couple there has been relatively good population growth, he says. Without more 1080, he worries those gains could be quickly erased – or push the wild kākāriki population to the brink. “You hit a mast year like we’re about to strike and you just take those massive hits.”

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