Plague warning: Maps reveal extent of 'mega mast'

Official maps released today have revealed the vast swathe of New Zealand wilderness under threat from a plague-fuelling "mega mast" - but officials say response plans can't be scaled up.

Forest & Bird is warning a nationwide rat plague is only about to get worse, and has pleaded with the Government and councils to increase their 1080 rat control programmes, before a stoat plague comes next.

A mast event is when trees such as beech trees seed, littering forest floors with an abundance of food for pests. A mega-mast is one where this seeding is widespread across the country.

In this year's event - the largest in nearly half a century - Department of Conservation (DoC) scientists have already predicted local extinctions of native birds, with some unprotected populations of orange-fronted parakeet, long and short tailed bats, rock wren and mohua particularly at risk.

DoC was responding with its largest ever predator control programme, estimated to cost $38 million and covering about one million hectares - or 12 per cent of conservation land.

This map shows areas of the North Island that are being covered by predator control operations this year. Image / Supplied

The operation would see 1080 poison applied across nearly 900,000ha of land, along with ground control - mostly through trapping - across 66,000ha.

Backed by a Budget boost of $81m, the programme was a big step up from those carried out in previous mast years, such as in 2016, covering 840,000ha, and 2014 and 2017, covering 600,000ha.

Areas of the South Island that are being covered by predator control operations this year. Image / Supplied

But advocates say it still won't be enough to save countless native birds from being eaten this year.

This map shows the distribution of beech trees, measured by milligrams of seed per handful. Image / Supplied

Forest & Bird says the maps make it clear how little rat or stoat control there is across most of the nation's forest and tussock land, and that local native species could easily become extinct as a result.

This map shows the distribution of rimu trees across New Zealand, measured by the percentage of those that have tips with old fruit that can be eaten by pests. Image / Supplied

This map shows the distribution of flowering tussock - providing food for pests - per metre squared. Image / Supplied

Debs Martin, from the Pelorus Bat Recovery programme, and Gillian Wadams, from Ark in the Park in the Waitakere Ranges, presented official maps at the organisation's annual conference, comparing the massive country-wide scale of this year's mega-mast, and the comparative paucity of rat and stoat control available to deal with it.

"Even with a growing number of community trapping groups, and the biggest investment ever made in biodegradable 1080 rat control, only 12 per cent of conservation land, or less than 4 per cent of the entire country, is being treated with aerial 1080," Martin said.

"Despite running an intensive trapping protect over 250ha in the Pelorus Bridge Scenic Reserve, rats are pouring out of the 166,000ha Richmond Ranges, where there is no predator control at all."

This was happening all across the country, she said, and as breeding season got under way, native birds and bats would have slim chances of survival.

"New Zealand desperately needs to get behind aerial 1080 as our best way of controlling rats across large or rugged areas, so birds, bats and other natives can breed and raise their young successfully," Martin said.

"While we can protect backyards and even suburbs with comprehensive trapping programmes, most of our forests have nothing at all – not traps, nor toxins.

"Our forests are experiencing a rat plague, just like our towns and cities are.

"The difference is that there is no way to trap in dense, steep and vast forests, and DOC are running the country's largest ever predator control programme, but still only covering 12 per cent of conservation land, itself only 30 per cent New Zealand's total land mass."

Martin argued that DoC needed extra money now - and the country needed to be better prepared for the next big event.

"As this crisis becomes even more apparent, we urge the Government to invest more in extra aerial 1080 this year," she said.

"Otherwise across the country our rarer bird and animal may become locally extinct."

DoC's director of national operations, Hilary Aikman, said DoC prioritised predator control to shield the most at-risk populations of native species, threatened forests and areas of high ecological value on conservation land.

The operation aimed to protect specific populations of kiwi, kākā, kōkako, kea, whio/blue duck, mohua, orange-fronted parakeet, rock wren, long and short tailed bats, native frogs, giant land snails and reptiles.

"Unfortunately, DoC cannot undertake predator control in all conservation areas where native species will be at threat from increased numbers of rats and stoats due to this year's forest mast," Aikman said.

"The current programme over one million hectares is as much as DoC staff and contractors can deliver this year."

DoC had been planning its predator control programme for more than a year with consultation with iwi partners, neighbouring landowners and other groups, she said.

"While it's not feasible to increase the size of this year's programme, there is some flexibility to include additional proposed sites if operations at some priority sites don't proceed due to rodents not reaching predicted damaging levels.

"DoC closely monitors rodent levels to inform whether each predator control operation is necessary."

Species on the brink named after Avatar, Titanic

Meanwhile, two of New Zealand's most threatened - yet just discovered - species have had their plight highlighted by being named after James Cameron blockbusters.

The two species of macro moth were named Arctesthes titanica and Arctesthes avatar, after the US director and Wairarapa resident's movies Avatar and Titanic respectively.

A.titanica's wetland habitat is under pressure from over-sowing, grazing, stock trampling and vehicle damage. Image / Supplied

Each were thought to be restricted to just a few alpine and subalpine locations around the South Island - A.titanica being found in wetland areas of the Von Valley of the Otago Lakes district, and A. avatar in a few wetlands in northwest of Nelson.

Therefore, both were considered particularly vulnerable to extinction and need to be "considered of very high priority for conservation", researchers wrote in the journal Alpine Entomology.

Because of its relatively large size, A. titanica, was named in reference to the Titans, the elderly gods in Greek mythology and the ship Titanic, which became the subject of the famous 1997 American epic romance and disaster film of the same name.

The moth's small wetland habitat was located in an area under pressure from over-sowing, grazing, stock trampling and vehicle damage.

A. avatar, meanwhile, received its name after Forest & Bird ran a public competition where "the avatar moth" turned up as the winning entry.

Just like the indigenous characters in Avatar, the newly described moth was especially vulnerable to habitat change and destruction.

A. avatar received its name after Forest and Bird ran a public competition where "the avatar moth" turned up as the winning entry. Image / Supplied

The study's authors - Wildlands Consultants ecologist Dr Brian Patrick, Lincoln University ecologist Dr Hamish Patrick and Manaaki Whenua - Landcare Research invertebrate researcher Dr Robert Hoare - noted the original avatars came from Hindu mythology, where they are the incarnations of deities, including Vishnu, for example, who would transform into Varaha the boar.

They concluded that future studies to monitor and further understand the fauna of New Zealand were of crucial importance for its preservation.

"Quantitative studies as well as work on life histories and ecology are particularly needed," they wrote.

"Already one formerly common endemic geometrid species, Xanthorhoe bulbulata, has declined drastically and is feared possibly extinct: its life history and host-plant have never been discovered.

"Without further intensive study of the fauna of modified and threatened New Zealand environments, we will be unable to prevent other species slipping away."

It's not the first time scientists have named threatened species after well-known films and figures to raise awareness of them.

In 2017, Canadian scientist Vazrick Nazar named a moth species found in California and Mexico Neopalpa donaldtrumpi.

Known for its yellowish-white head scales being reminiscent of Donald Trump's hair, the moth was given its name because Nazari stated that he wanted "to bring wider public attention to the need to continue protecting fragile habitats in the US that still contain many undescribed species".