The Current Status of Predators on New Zealand Offshore Islands

Posted by Zach Carter

New Zealand is committed to preserving its uniquely rich biological heritage with Predator-Free New Zealand (PFNZ). This audacious programme is focused on ridding the country of the three most biologically and economically harmful mammalian taxa by the year 2050 (Innes, Kelly, Overton, & Gillies, 2010). Pests targeted for eradication include rodents (Rattus rattus, R. norvegicus, R. exulans), mustelids (Mustela furo, M. ermine, M. nivalis) and the common brushtail possum (Trichosurus vulpecula). These mammals predate upon native biota and threaten to undermine New Zealand’s most lucrative industries, including tourism and the primary industries. There is unilateral support for PFNZ, but how close are we to actually achieving this goal on New Zealand’s offshore islands?

If we exclude large islands that are source to substantial pest populations, including Stewart Island (Rakiura) and Great Barrier Island (Aotea), and islands that cannot support mammalian life for extended periods (islands < 5 hectares, ha), 85 offshore islands (islands ≤ 50 kilometres from the mainland) currently host PFNZ mammal pests. Insofar, 87 offshore islands have been eradicated of mammals since New Zealand began systematic removals in 1980 (Figure 1). This means that over half (50.5%) of the islands with a historical pest presence have been eradicated!

Figure 1: PFNZ mammal eradications that have occurred on New Zealand offshore islands from 1980 through present.

If we investigate the total amount of island area eradicated in this dataset, we paint a slightly different picture; 84,300 ha of island area currently host mammal pests, and 24,200 ha have been eradicated. This means that only 22.3% of island area historically hosting mammals have been eradicated. Note, this dataset includes only cases of confirmed pest presence (islands with an unknown status were excluded) and excludes incursions as being considered confirmation of pest presence. Moreover, these numbers do not coincide with other eradication estimates that use different geographical boundaries or different pest species (e.g.(Towns, West, & Broome, 2013).

Admittedly, there is much work left to accomplish. This does not mean that PFNZ is impossible, though, only that it will be an uphill battle. In order to keep with the designated timeline, multiple government agencies and private groups have come together seeking creation of new (or “future”) control technologies that can address issues of ethical and technical concern. Transformative genetic control tools (including virus-vectored immunocontraception, RNA interference, and transgenic ‘Trojan’ approaches), and novel takes on current-day technology (including automated self-resetting traps, remote monitoring, and highly attractive lures) are being designed to target specific species in a manner that is cost-effective, environmentally benign, and exceeds the public conception of humaneness (Campbell et al., 2015). Such tools will be essential to the success of PFNZ. If they can be implemented in a timely manner, New Zealand will be well on its way to being the first nationwide endemic sanctuary.

Zach Carter is a PhD student at the University of Auckland in the School of Biological Sciences. He works with Dr. James Russell prioritising eradications of mammal pest species throughout New Zealand.


Campbell, K. J., Beek, J., Eason, C. T., Glen, A. S., Godwin, J., Gould, F., . . . Ponder, J. B. (2015). The next generation of rodent eradications: innovative technologies and tools to improve species specificity and increase their feasibility on islands. Biological Conservation, 185, 47-58.

Campbell, K. J., Beek, J., Eason, C. T., Glen, A. S., Godwin, J., Gould, F., . . . Ponder, J. B. (2015). The next generation of rodent eradications: innovative technologies and tools to improve species specificity and increase their feasibility on islands. Biological Conservation, 185, 47-58.

Innes, J., Kelly, D., Overton, J. M., & Gillies, C. (2010). Predation and other factors currently limiting New Zealand forest birds. New Zealand Journal of Ecology, 34(1), 86.

Towns, D. R., West, C., & Broome, K. (2013). Purposes, outcomes and challenges of eradicating invasive mammals from New Zealand islands: an historical perspective. Wildlife Research, 40(2), 94. 10.1071/wr12064

Community conservation: ‘HIMBY’ not ‘NIMBY’

Posted by Margaret Stanley @mc_stanley1

I recently participated in a community conservation forum, when a community engagement colleague coined the acronym ‘HIMBY’. I was exasperated by what I perceived as the community not being able to see the ‘big picture’ of evidence-based strategy around pest management and restoration.

 “It’s the opposite of NIMBY [Not In My BackYard]” she said. “It HAS to be In My BackYard – HIMBY”. And she’s dead right. This particular scenario is increasingly raising its head as community groups voraciously compete for conservation funding and action.

Of course we desperately need highly activated communities to be engaged in conservation and restoration. We can enhance biodiversity over a larger area with limited resources when community groups and volunteers give their time and energy for free. It’s also important to have place-based conservation – this allows a sense of ownership and community buy-in that allows sustainability of people and groups over time. Ecologists have long since recognised that ecological science alone won’t solve conservation problems, and social science and community partnership is a critical cog in the conservation wheel.

However, we also need to remind our communities about the risks of ‘HIMBY’ and community-based conservation. One of the major risks of a national emphasis on community-based conservation is that funding could be diverted away from areas that don’t have people – then we could end up in a situation where much of our conservation action is not taking place on land that is representative of different ecosystem types/biodiversity. In fact, we know that community conservation is biased towards coastal forest ecosystems, where people are concentrated.

At a local level, where funding and resources are prioritised and allocated within regions or cities, ‘HIMBY’ is alive and well. Community groups within cities/regions are understandably vying for resources. However, prioritisation of pest management must incorporate more than community activation. Firstly, it must be cost-effective and have preventative outcomes, rather than the ambulance at the bottom of the cliff. We should prioritise prevention. The Treasure Islands programme which funds pathway biosecurity to prevent pest invasion on Hauraki Gulf Islands both 1) protects assets with previous large investment in removing pests (e.g. Rangitoto-Motutapu Islands) and 2) prevents new invasions, thereby saving money in the long term. We know how cost-effective it is in medicine to vaccinate rather than belatedly treat the disease.

Given the impacts of Aotearoa-New Zealand’s invasion debt, we have to continue to ‘treat the disease’ and reduce pests and restore habitat. But the ‘where’ should be decided strategically. Yes, the degree to which a community is activated is a key factor in prioritisation along with other cultural and societal factors, but ecological factors (beyond our backyards), such as level of pest infestation, the value of the conservation assets within sites, and habitat connectivity, should be key factors in deciding where conservation actions should take place to achieve the best outcomes for biodiversity across the city or region.

Invasion Curve Animation  – explains the principles of prioritization for pest management based on cost-effectiveness (You Tube: ‘ Invasion Curve Animation Biosecurity Council of WA’).

Although we’re primed as humans to be highly attached to ‘our backyard’ and want the best outcomes for it, we need to see the wood for the trees. This is why larger-scale conservation visions, such as the North-West Wildlink and Cape to City are becoming increasingly important. If we can all buy into the larger landscape scale conservation vision, then we will be willing to see that the priorities for action/$$ spent might not be in our backyard, but over the fence, in someone else’s backyard. We’ll also understand that by taking action in the neighbour’s backyard, we will benefit from the biodiversity spilling over into our backyard.

Time to look up from our backyards and take on the larger vision.

Dedicated to the champion work of conservation staff within agencies engaging with communities, and also to those champion activators within our communities, rallying people to conservation action!

Margaret Stanley

Dr Margaret Stanley is an Associate Professor in Ecology, School of Biological Sciences, University of Auckland. Most of her research is applied ecology, working to improve outcomes for biodiversity.