Summer Science: The battle for our islands

A general view over the Antipodes Islands - recently declared pest-free. Photo / Finlay Cox

Science reporter Jamie Morton talks to Auckland University conservation ecologist Dr James Russell about the ongoing battle to sweep our islands clear of pest predators.

In 1964, conservation pioneer Don Merton and others declared Maria Island in the Hauraki Gulf predator-free. What was the significance of this and what has happened since in New Zealand island conservation?

The significance of this conservation action only became clear in retrospect many decades later.

From reading the historical reports, even the practitioners involved treated it with a level of doubt, that they could actually have permanently removed rats from a 1 ha island.

Even in 1976 scientists were still arguing over whether anything larger than 1 ha was possible.

It wasn't until a few pioneering scientists from DSIR and Wildlife Service started being experimental about it in the 1980s that we realised we could consistently repeat eradications.

From that work, they also learnt what the "recipe" was, and we have been applying it since to over 100 islands around the coast of New Zealand.

Most importantly, this has created predator-free habitat for so many of our native species, which we now associate only with island refuges.

Why is island conservation so important for preserving New Zealand's threatened species and where would they be without them? What species might we have lost?

Species are going extinct around the world and the first step in their conservation is identifying the most prominent threats.

A helicopter view of the Antipodes Islands. Photo / Finlay Cox

These are not always obvious.

Islands around the world are unique places because predatory land mammals never evolved on them, but apart from a few forerunners, it took some time for scientists and conservationists in New Zealand to recognise the role that mammal predation played in New Zealand species extinctions.

This has also been the case throughout islands on the rest of the world.

"Island conservation" thus encapsulates both identifying or creating predator-free island habitat, and then reintroducing species at threat from predation to those islands.

Without the great reservoir of offshore islands many native species of birds, reptiles and invertebrates would be left clinging to existence, or extinct, on the mainland - our two biggest islands - where we can't currently achieve permanent eradication.

This includes species such as kakapo, takahe, tieke, tuatara, Hauraki skink, Duvaucel's gecko, and wetapunga.

Do you think most Kiwis would be aware of this work?

New Zealand has some amazing conservation stories, such as rediscovering the takahe and New Zealand storm petrel, and saving the black robin and kakapo.

A helicopter joins an anti-pest operation on the subantarctic Antipodes Islands. Photo / Finlay Cox

Our children are raised on these stories and today they have become a part of our national identity - part of what being a Kiwi means.

This means we have a globally unprecedented level of support for conservation action in New Zealand.

But there remain many more untold stories such as the conservation of our native reptiles which number over 100, or the fact that New Zealand has the highest number of endemic seabirds in the world, also nearly 100.

New Zealand has also saved plants from extinction, such as the Three Kings Vine, from a last single individual known on an island. It's now found in gardens throughout Auckland.

What are the big challenges that face conservationists in trying to eradicate predators from islands? And how easy can they be re-invaded?

Eradication of introduced mammalian predators on islands in New Zealand is now shifting focus to islands with are partly or wholly privately owned - most of the Department of Conservation-owned islands are now predator-free.

Navigating the windswept hills of the Antipodes Islands. Photo / Finlay Cox

This requires coming to an agreement with the island community about what their conservation priorities are, and what the most appropriate method for eradicating the predators.

Another big challenge is keeping up with ourselves and preventing predators we have eradicated previously from returning to islands, by either swimming or stowing away.

We have evidence now that on a good day mustelids such as stoats can swim up to five kilometres, and rodents such as Norway rats up to two kilometres.

With mammalian predators removed we are also able to shift our focus to other pest species we might want to eradicate, such as Argentine ants or moth plant.

These new frontiers of eradication are both challenging and exciting.

Eradicating ants requires finding every last nest, while eradicating plants requires exhausting the seedbank in the soil.

What would you say has been our most significant victory in clearing islands and why?

It's really hard to identify a single eradication.

A view over Great Mercury Island. Photo / James Russell

As the first one Maria Island (Ruapuke) is always important, but so was the largest one when we eradicated rats from 11,300 ha Campbell Island in 2001, still our biggest today, with New Zealander's also running the large operation on nearby 12,875 ha Australian Macquarie Island in 2011.

Closer to home, the eradication of eight mammal species simultaneously from Rangitoto and Motutapu Islands with a combined area of 3,842 ha, and then preventing them being reinvaded despite a number of biosecurity incursions from both swimmers and stowaways, really drives home that this kind of conservation can be done in our own backyards where everyone can access it.

There are over 100,000 visitors a year to Rangitoto and Motutapu, and more and more threatened native species being reintroduced every year.

This year Argentine ants were also declared eradicated from Tiritiri Matangi Island after many years work.

What work have you been leading most recently and what has that involved?

This year I was pleased to see the Million Dollar Mouse project to eradicate mice on Antipodes Island go ahead.

I visited Antipodes Island in 2011 and 2013 to undertake studies on the population biology of the mice, and what impacts eradication would have on other species, with other researchers from NIWA and DOC.

This was a fantastic project as it leveraged philanthropy to undertake one of the most logistically and technically challenging eradications to date.

A native parakeet on the Antipodes Islands. Photo / James Russell

It will be really exciting to confirm this eradication was successful in the next few years.

I've also been working in the office developing software tools which can help eradication managers, such as Rapid Eradication Assessment, which we've been trialling this year for events such as the first incursion of a rat on to Ahuahu (Great Mercury Island) after cat and rat eradication was completed in 2014.

We're currently trialling some of the new devices on the market on small islands to see if we can achieve rat eradication using alternative tools, such as self-resetting traps.

I've also just taken over leadership of the National Science Challenge for Biological Heritage project in high tech solutions for invasive mammal pests, which will start in 2017 to hopefully provide the kind of "blue sky" science required for a Predator Free New Zealand.

I'm still reeling from the Government announcement for Predator Free New Zealand 2050.

I've also been fortunate to be advising projects in French Polynesia and Brazil about invasive species management, which has involved some very enjoyable but at the same time challenging field expeditions.

A view over the Antipodes Islands. Photo / James Russell

What has the rest of the world learned from our efforts here in New Zealand?

Invasive species are really exploding on the global scene, for the first time countries around the world now want to manage the risks and threats they cause.

New Zealand has a long and proud history of both agricultural and biodiversity biosecurity dating back over 100 years, and we've been able to go to international meetings this year, such as the IUCN congress in Hawaii and the UN biodiversity conference COP13 in Cancun and lead the world by committing to PFNZ2050.

The rest of the world is able to look to New Zealand and see that we are putting our money where our mouths are - we are both committing to bold targets but have a demonstrated track record of being able to achieve them.

By showing that it's not just talk but action in New Zealand, I think this has been a really good news story for what had been a pretty crazy year in other spheres.

How will this work benefit the recently-announced goal to make the country predator-free by 2050? Will they serve as a template?

The many attempts to eradicate predators, and other pests, from around New Zealand provide a rich dataset of experiments.

Some of these eradication experiments have failed, but this has still helped as to learn more and develop better tools and techniques to be successful elsewhere.

A modern eradication is an exercise in project management, and only a small amount is actually fieldwork or science.

A lot of time is also spent talking to communities and obtaining consents.

Our experience managing these types of projects across New Zealand means we will be well placed to scale-up to larger and larger zero suppression projects such as zero Cape to City (26,000 ha) and Project Maunga (34,000 ha), or simply linking together all the small community projects across New Zealand in to a giant network.

Still, how will taking the fight to the mainland be much different from what we've achieved on islands and what kind of new technology will we have to draw on?

The mainland of New Zealand is still only two very big islands, but it has many more species interacting with one another.

We can no longer just focus on one or a few pest species at a time, we will have to manage more of them all at the same time, or eradicate them all at once.

This requires better biological science expertise.

We also have to talk to all elements of the community, both supporters and detractors, to understand where there is disagreement and work towards shared solutions.

This requires better social science expertise.

The Antipodes Islands are home to some colourful seabird species. Photo / James Russell

Both of these require investment in the underlying scholarly knowledge, but we will also need to develop new technology, such as in the National Science Challenge high tech solutions to invasive mammal pests project or through R and D by Zero Invasive Predators.

Some of the new technologies will leverage the major advances made in molecular biology and genomics over the past few years, potentially even gene-editing tools, but other opportunities will come from developing new chemical lures and toxins, to engineering new devices such as traps and bait stations, to using advanced technologies such as drones and automatic identification.

Back to island conservation, where would you see these offshore fortresses sitting in our conservation efforts say, 50 years from now?

Small islands always have a wonderful sense of nostalgia and escapism - it's what always draws me back to them.

I visited Slipper Island resort recently and was exactly struck by that powerful combination; an operational farm with biodiversity restoration and conservation.

I think people will always be drawn to islands for this Robinson Crusoe effect, but even once we remove the predators of Predator Free New Zealand from the country, I think islands will always continue to serve as the next experimental laboratories for ecological and conservation research.

There is always another pest species just around the corner, and on islands we can practice and hone our abilities to eradicate these species before committing to larger more expensive projects on the mainland.