Aotearoa New Zealand, and New Zealanders, are extraordinarily good at what we do. A recent example: look at our record-setting gold medal haul at the Commonwealth Games. Hard work, painstaking attention to detail, rigorous training and learning from failures were all part and parcel of competing in Birmingham, and it all paid off.

Exactly the same is true of our conservation successes, yet people are much less familiar with our exemplary record in this area. So it’s great to see this paper published, because it puts our national efforts in a global context when it comes to eradicating invasive pests from islands. The paper, from an international team of authors including some based in Aotearoa, uses information from a global database of island invasive species eradications.

The team looked at successful eradications (defined as complete removal) of invasive mammals and birds, and even an invasive lizard. Importantly, they also included eradication ‘failures’ – for example, where a pest re-establishes after a removal attempt. Invasive species in the database include birds, rabbits and hares, rodents, mustelids, pigs, feral cats, lizards, dogs and foxes, and many more.

Eradications of invasive species from islands is quite a specialist area of conservation, yet critically important globally. This is because islands are often hotspots of unique biodiversity. Aotearoa – both our larger islands and our numerous smaller ones – is no exception. Many of our native plants and animals are found nowhere else in the world. The authors show that Aotearoa’s contribution to reversing the depressing trend of extinctions of endemic biodiversity on islands is globally significant and deserves to be celebrated.

Not only have we done much to protect our unique biota, but we can also hold our heads up high when it comes to achieving international targets that we have signed up to (for example the Convention on Biological Diversity’s Aichi targets). The paper shows that particularly in the last half-century or so, Aotearoa contributed to nearly a quarter of all successful eradications of invasive species on islands globally.

The authors highlight some interesting trends. For example, while the total number of successful eradications has levelled off in the last decade, the total island area eradicated continues to increase. This means that eradications are successful on fewer, larger islands. Often these islands are inhabited by people, which points to the ever-increasing complexity of island eradications and the need to build relationships on inhabited islands early to ensure that people feel as if they are part of the solution.

The authors also highlight the need for ‘niche’ technological innovations – new tools in the toolbox such as species-specific toxicants or new methods to rapidly detect and respond to invaders. Many of the insights will be valuable for us here in Aotearoa as we tackle ever-larger islands such as Rakiura and Aotea as part of our efforts to become predator free. The findings help us understand community concerns on the one hand, but also motivations and enthusiasm for persevering with eradications (e.g. tourism opportunities) on the other.

Finally, this study demonstrates the value of a database such as the global database of island invasive species eradications maintained by the IUCN’s invasive species specialist group and supported by organisations from several countries including Aotearoa. The insights gleaned from an analysis like this can help inform eradication attempts on many other invasive species (e.g. fire ants or plant pathogens) and also help us learn what doesn’t work (thereby minimising expenditure on wasted attempts). Without that database, such a study would not have been possible.

This is a great review of the history of island pest eradications, and highlights Aotearoa's leading role in the development and implementation of these conservation success stories. Aotearoa has led this field both because of the innovation culture in conservation we have, but also out of necessity due to the ongoing decline of many of our taonga species. 

The study also shows the pace of island eradications is slowing both internationally and within Aotearoa. This is because we have largely completed eradications on the 'easy' islands. Now we need to move to larger islands with permanent populations, and the challenges of scaling up to these require significant investments in research, and in fostering true partnerships with communities.

The next obvious and exciting steps are islands like Rakiura, Aotea, and Pitt, and while the challenges of achieving pest free status on these islands are daunting, the benefits for threatened species will be huge, and the lessons learned in such programs will bring us closer to mainland landscape level control and eradication.

This global synthesis analyses data from over 1,500 eradication attempts to understand global trends in island eradications. It’s exciting to see these trends and patterns in island eradications at such a large scale, and they represent an enormous effort by the authors to pull together an impressive amount of gnarly data.

The results are also heartening, demonstrating that 88% of eradications have been successful. While the eradication success rate only increased a small amount through time, the study shows that the vast majority of eradications attempts are successful.

In addition, we are successfully tackling eradications on larger and more complex islands. This bodes well for future eradication attempts on larger islands such as Rakiura or Aotea, although it must be noted that the scale of these eradications is entirely unprecedented. Inhabited islands like Rakiura or Aotea bring their own challenges to island eradications, but this paper shows an encouraging trend in achieving eradications on larger inhabited areas through time.

Although the authors point out that eradications on inhabited islands are more complicated, they also make the excellent point that eradications that happen where people live can have cascading social benefits as well as biodiversity benefits.

There have been several recent studies of contributions of island pest eradications by country, and NZ has consistently been near the top in terms of the number of successes. Most (but not all) of the islands have been uninhabited. Predator Free 2050 will require eradications in inhabited areas, and this is being investigated on some large inhabited islands here (e.g. Rakiura/Stewart). Complex social issues may be involved at such locations and the methods that are socially acceptable may make rat eradications particularly challenging.

Some methods such as the aerial spread of baits have become increasingly effective. They may also be controversial, but there are examples recently where well informed local communities have been willing for such methods to be applied even when there has been historic opposition. So the key to social acceptability is good communication, early involvement in planning, and thorough examination of the options available. Of course, everyone also needs to agree on the goal.

This paper is the first summary of eradication attempts on invasive vertebrates on islands worldwide and is an excellent and timely summary. It shows that eradications can be effective and are a vitally important conservation tool.

New Zealanders should be very proud of the role that the New Zealand Wildlife Service (that became part of DOC) played in pioneering these techniques.

This work highlights however the worrying issue that eradication attempts have declined in recent years.

What is not mentioned is that this some of this decline may be because the number of small easily accessible islands with invasive species have declined. The really tricky ones remain, like the inhabited islands such as Norfolk and Great Barrier Island and the inaccessible and huge islands, for example Isla Guafo in Chile and New Zealand's own Auckland Islands. A failed eradication attempt was made at one of the most geographically isolated places on Earth – Henderson Island in the central Pacific.

Another issue only tangentially mentioned is that concerns over the poisons used in these eradications has made it more difficult to get support for funding eradications, highlighting the need for more research into environmentally sustainable techniques. An issue in the 'too hard basket' is the eradication of invasive rats on islands with native rat species and other small mammals, for example islands off the coast of Chile.

The paper provides the first quantitative documentation of eradications of invasive species from islands at a global level. It is possibly the most comprehensive global documentation of any conservation initiative. The basic trends documented as well known to people working in New Zealand conservation, i.e. that there has been an acceleration of island eradications since the 1960s, and since the 2000s this has been facilitated by scaling up operations to progressively bigger areas. It was this progressive scaling up that led to the Predator Free 2050 programme.

The most important thing is not that invasive species continue to be eradicated but that this leads to huge biodiversity gains in the areas treated, helping to counter the ongoing loss of global biodiversity.

Breakthroughs in rodent eradications on islands have occurred in three waves. In the 1980s New Zealanders fine-tuned ground-based rodent eradication methodology, in the 1990s we pioneered the use of helicopters to treat much larger islands, and in the 2000s we gained the confidence to detect and remove rats reinvading islands. The next breakthrough will be the ability to work on the largest islands which also have human inhabitants. Throughout this time New Zealanders have always been exporting globally this knowledge, capability and technology.

New Zealand has reached the halfway mark for mammal eradications, over the past century having cleared invasive mammals from half the islands on which they exist. We have to continue, indeed even accelerate, this commitment to remove invasive mammals from the remaining islands, and achieve our Predator Free goal by 2050.