Experiments in Island Hopping

Paddy Woodworth

 

Tiritiri Matangi

Maritime island, near Auckland.

http://www.tiritirimatangi.org.nz/

Introduced predator history: cleared of rabbits 1920, and of kiore (the rat introduced by Maori) in the 1980s.1 No other mammals. Forest cleared from intensive cover to fragments, restored to 60% cover by the 1990s.

Issues: Tiritiri Matangi was a pioneer for new generations of island sanctuaries. The government designated it as a reserve in 1971, but it was assumed that spontaneous regeneration would restore indigenous forest to an island almost entirely cleared by centuries of occupation and farming. A dense carpet of grass, however, prevented trees from propagating beyond remnant native patches. A very active citizen conservation group, Supporters of Tiritiri Matangi (SoTM), sprang up in response to this apparent failure. It campaigned for active regeneration of vegetation, for the reintroduction of rare native birds, and, most controversially, for the active encouragement of visitors from nearby Auckland. The conservation assumption at the time was that humans were always a threat to reintroduced birds and many scientists strongly opposed this initiative. John Craig of the University of Auckland was a prominent exception, and he backed SoTM’s argument that offering citizens controlled opportunities to interact with rare species was a marvellous way of building public support for conservation. Tiritiri Matangi’s location, less than an hour from Auckland, made it an ideal visitor site. Volunteer restorationists planted 25,000 trees a year for 10 years, incentivised by close contact with birds which could be seen nowhere else in the wild at the time. Volunteers continue to collaborate with DOC as guides for the 35,000-plus annual visitors, in a co-operative management agreement with DOC. Twelve bird species and the tuatara have been reintroduced, and most populations are increasing well. They are valuable ‘insurance’ against disease or disaster elsewhere, and sources for further reintroductions on other islands and, more and more, on the mainland. The island continues to provide excellent research material, not least on how the volunteer and visitor experiences are changing people’s perceptions of, and attitudes to, biodiversity.2

Observations: It was certainly a treat to enjoy the presence in the wild of substantial numbers of native forest birds, including bellbird, tui, whitehead and saddleback. However, the occasional feeding station does echo the ‘zoo effect.’ That might otherwise be minimal here, given that (with the exception of the takahe), all birds are flighted, with complete freedom of movement.3 The zoo effect was again amplified by the almost absurdly trusting behaviour of a pair of takahe, which of course are flightless. They allowed me to approach closer than any self-respecting farmyard hen would have allowed, though they emitted heart-rending cries of apparent anguish if I walked between them. Others have found them less friendly, with a penchant for tasting trouser bottoms, according to one visitor, who remarked that it was the first time he had been “nipped by an endangered species.”4

 

Mana Island

Maritime island, near Wellington

www.manaisland.org.nz/

Introduced predator history: Only the mouse. Population exploded to 15 million after farming was abandoned in 1980s, almost eradicating key communities of threatened wetas, skinks and geckos, which have recovered after mouse eradication was completed in 1990.

Issues: Colin Miskelly’s thoughtful 1999 ecological restoration plan for the island5 (under revision at the time of writing) boldly confronted a number of difficult questions. Many arose from the long experience of conservation on nearby Kapiti Island (see below):
Should animals that were never native to Mana, but are urgently in need of mammal-free environments, be part of the restoration? His answer was often affirmative, as in the case of the takahe, which now has a relatively large population on the island. But it was carefully calibrated to avoid mistakes made on Kapiti. Such animals should pose no risks to species indigenous to the island, nor should they be at risk themselves, through hybridisation, competition or predation. But even when species would naturally share a site, numerous problems can arise during the restoration process. Miskelly noted the complex budget of restoration costs and benefits represented by large and rapidly increasing numbers of the pukeko (purple gallinule). Their voracious grazing was undermining an ambitious programme to revegetate the island with native plants.6 They were potentially helpful as cross-fosterers of the eggs of the closely-related takahe. But the density of their population also presented a disease risk to takahe, and—their appetites again—they were plundering takahe feeding stations. Finally, they represented a potential predation threat against the eggs of brown teal, a rare endemic struggling to establish itself on Mana. His solution: while the developing forest area will of itself reduce the pukeko, some control—culling—will be necessary.7

Observations: Stormy weather made for a heart-breakingly brief visit, under Miskelly’s guidance. We found shore plovers, a rare endemic released here from a captive breeding program, on the pebble strand as we landed. Culling of (native) black-backed gulls has contributed to the plovers’ short-term survival on Mana. Triage, triage. However, their natural instinct to fly to mainland estuaries in search of food leaves them heavily exposed to predators, and reintroduction success is still an open question. Islands may keep alien predators out, but they cannot keep native species in, if they can fly or swim.

Miskelly took us to one of the island’s seabird colonies, where we checked a slowly fledging sooty shearwater chick, and also a pair of diving petrels, surprisingly roosting in their underground burrows during the day. Two things made a big impression on me here.

Firstly, the technology involved in restoring a seabird colony was yet another reminder that we often need to do glaringly ‘unnatural’ things in wild places in order to bring nature back to (something like) itself. The cliffs on Mana are stippled with solar panels to power louderspeakers; they broadcast electronic reproductions of cries that attract pelagic birds to breed there. Pre-fab burrows, constructed with ribbed plastic tubing, are available to new residents. Sophisticated heat detectors (with built-in USB keys for quick data downloads) record roosting patterns.

At the other end of the nature/technology spectrum, I learned for the first time the rather obvious fact—once you think about it—that seabirds are ‘foundation species’ for island ecosystems. They often contribute the first major nutrients (droppings, regurgitations, their own dead flesh) on bare rock, which enable new plant communities to establish. Invertebrates and reptiles flourish through co-habiting in their burrows. While NZ restoration may often favour species over ecosystems, the restoration of seabird colonies constitutes the rebuilding of the system from, quite literally, ground level. This is the ecological basis for the translocation of hundreds of fairy prion (Pachyptila turtur) fledglings to Mana, in the hope that they will re-establish the huge colonies they once had here, and on many parts of the mainland.8

 

Zealandia

Mainland island, fenced

www.visitzealandia.com/

Introduced predator history: no less than 13 species, including domestic cats, eradicated; however, a mouse population, albeit greatly reduced, remains a problem.9

Issues: this sanctuary, confusingly also known as Karori, is remarkable in several ways, but especially for its location —a 10-minute drive from parliament buildings in downtown Wellington. As such it has huge potential for public education. It also has a string of conservation ‘firsts,’ including first fenced mainland island, first reintroduction of little spotted kiwi to the mainland in 100 years (now breeding very successfully), and first breeding tuatara on the mainland in 200 years. The project wisely highlights the 500-year timeframe it has set itself to achieve its ambitious goal: restoring the area ‘as close as possible to its original state,’ by which it means ‘the day before humans arrived.’ A clearer statement of the old aspiration to restore to a pre-settlement past could hardly be made. Great swathes of alien vegetation remain to be removed, alien predators still occasionally penetrate the fence. Two endemic reintroductions, the bellbird and the hihi, especially the former, are often lured across the fence by the attractions of surrounding gardens, where exotic plants offer tempting food supplies ‘out of season.’ And there, of course, they are predated by cats.
In a very interesting twist, alien Australian Banksia species have been introduced to Zealandia, in the hope that their flowers and fruits may help to keep these species on site. The reasoning here is complex, and not without irony. But to bring in a new alien, which can become invasive in NZ, as a restoration aid to a site that is still being cleared of other alien plants, is obviously a balancing act that requires very careful assessment.

The biggest issue is whether it is feasible, or even desirable, to reintroduce the complete suite of native species once present in the area—there are formidable targets for reptiles, insects, plants and fish as well as birds—in a such a small and vulnerable space. The driver for reintroductions so far has been what we might call the charismatic species imperative: “We had to get the birds people want to see in first,” says conservation manager Raewyn Empson, who struck me as both remarkably visionary and remarkably pragmatic. “The reintroductions have not been necessarily in the order we would have chosen from a strictly ecological perspective.”10 She acknowledges that genetic impacts of inbreeding will have to be watched very carefully also.

Observations: There is a refreshingly stark honesty about the entrance exhibits. At what other conservation project would masses of national and international tourists be greeted by in-your-face examples of a poison bait station for stoats and a humane kill trap for cats? Or by a lawn, used for weddings and other ceremonies, where the buried remains of 3000 eradicated possums are fertilising the grass? Inevitably, in such a small fenced space (225 ha or a little less than one square mile) the zoo issue raises its head again and again. Visitors crowd around feeders11 often festooned with incongruously large concentrations of very rare indigenous birds, like hihi, saddle-backs, and kaka. And it also arises in conjunction with the size-related question of how native species, predators and prey, can co-exist in small spaces with fixed boundaries. The nationally threatened North Island subspecies of weka (Gallirallus australis greyi) was among the first species to be reintroduced. All well and good, but this aggressive rail has had to be segregated, by internal gates and fences, from the also endangered tuatara. The weka poses a threat, too, to the survival of other indigenous ground-nesting birds, reptiles and insects in such a restricted area. And the reintroduction of tomtits has failed entirely, despite some initital breeding, due to hostile competitive behaviour from New Zealand robins. Driven beyond the fence, they were presumably predated. Clearly, very few mainland islands, if any, are going to be large enough to be able to accommodate a full suite of the species appropriate to their habitats.

 

Pukaha Mount Bruce

Mainland Island, unfenced.

www.pukaha.org.nz/

Introduced predator history: all significant mammal threats present, but controlled by poison and trapping

Issues: This is an historic captive breeding centre12 that doubles as a small zoo of native wildlife. Over the last 10 years it has set up a mainland island in its hinterland, a 940 ha remnant of the ‘70 mile bush’ once famous for its biological treasures, and mostly torn down and burned in an intense burst of clearances in the 1870s and 1880s.

In an interesting sideswipe at other island sanctuary models (like Mount Bruce, administered or supported by DOC!), its website declares rather combatively: “We made a conscious decision not to hide the birds on islands or barricade them behind predator-proof fences,” and then adds: “But this means we have to stay on top of the predators with an aggressive pest control programme.”

A 2010 review13 of its restoration program stressed the benefits derived here from being surrounded by a 3000 ha of agricultural buffer zone, where mammals, especially possums, are also controlled by poison bait stations. This is part of a nationwide campaign to eradicate bovine tuberculosis, carried by possums, which provides a strong basis for consensus between farmers and conservationists on eradication. However, the author also notes concerns about poison residues in livestock, as well as urging the staff to tighten up their monitoring regimes.

Observations: Actual zoo and unfenced forest make an interesting contrast here. I had eyeball-to-eyeball views of a kokako, a very rare endemic bird the size of a small crow. Its plumage is ash-grey, and it sports a black Zorro mask and a shocking blue wattle. But it was behind wire-netting, and it approached me so closely because, I suspect, visitors often ignore the no-feeding sign. Kokako bred at Mount Bruce have been released into the sanctuary forest, but a walk there revealed no native birds at all, except occasional tui and New Zealand pigeon (kereru), both relatively easy to see outside reserves. Disappointing as that might seem, it was really only right and proper. It was a damp overcast day, which makes unlikely weather for finding forest birds, and in any case, a dozen kokako in a vast forest canopy should be hard to find. There are no feeders in these woods. But of course, apparently birdless forests will not attract as many visitors as Zealandia, where ‘wild’ birds sometimes seem to hang off every branch. It’s a familiar dilemma of conservation. How do you reconcile the need to attract the public—and public money pays for most reserves—with restoration of even a semi-natural environment? As a compromise, the staff organise a spectacular feeding display daily at the forest’s edge, which draws up to a score of extrovert kaka into the open.

Mount Bruce also runs a powerful education programme. The kiwi house, for example, offers opportunities to see the bird in a simulated nocturnal setting. It also provides dramatic and accessible data on the North Island brown kiwi, which continues to decline at a rate of 2% per annum due to mammal predation. Only more poison, the posters here argue, can save New Zealand’s iconic bird. There are also sinister exhibits on some of the villains in this drama—including ferrets, cats, possums and, oh yes, Homo sapiens, all straight out of Madame Tussauds. Not for nothing is this Centre one of the sponsors of the Whack-a-Rat campaign.

 

Kapiti Island

Maritime island, ‘island mainland’

http://www.doc.govt.nz/parks-and-recreation/places-to-visit/wellington-kapiti/kapiti/kapiti-island-nature-reserve/

Introduced predator history: Most threats were present when Kapiti (1965 ha) was declared as one of New Zealand’s first nature reserves in 1897; most of its forest had also been cleared. Goats were eradicated in 1928, followed by cats, deer, sheep, cattle, pigs, and dogs. The first total clearance of possums from an island was completed there in 1986. The last remaining alien mammals, Norway rats and the Maori-introduced kiore, were exterminated by Brodifacoum in 1996.

Issues: The history of conservation on Kapiti encapsulates changing attitudes to restoration over more than a century. The focus on mammal eradication has been constant, and advanced with technical/chemical developments. But the early conservationists wanted to squeeze as much as possible onto this particular ark. They introduced numerous birds that had never been native to the island, and an early caretaker brought in thousands of plants, aiming to create “an interesting botanical museum, where plants from all over New Zealand can be seen.”14

In the early 1980s, this “menagerie-building style” was initially replaced by a plan to simply conserve everything that already existed on the island at that point. Then that too was superseded by a vision of restoration based on a much broader ecosystem approach, greatly facilitated by the removal of rats. The consequences of indiscriminate introductions, even of native species, to an island context, have been instructive. Some plants have become weeds15—that is, they have become aggressively invasive— and are now being eradicated. Hybridisation of both kiwi and weka species and subspecies is widespread. This means that, as things stand, the island cannot now be used to host new populations of these species, because the incoming birds would also hybridise, diluting still further the genetic banks of rare or scarce endemics. For the same reason, Kapiti kiwi and weka cannot themselves be used as a bank to launch new populations on other sites cleared of mammals.

Colin Miskelly, in a thought-provoking essay, points out that no weka species had ever existed naturally on the island.16 Their presence today impedes the introduction of a whole range of species that do have a long history there, from skinks, weta and tuatara to burrow-nesting seabirds and snipe. However, he cautions against adopting, in this unique historical context, “a purist approach to ecological restoration.” Eliminating hybrid kiwi and weka would be most unpopular in the general conservation constituency, and probably very confusing to the general public. So he argues for a compromise: “We need to work with the legacy of our conservation forbears to create a viable, robust ecosystem that will continue to be treasured by current and future generations.”17

And, in a nice piece of lateral thinking, he argues that Kapiti should be considered as “a chunk of the mainland conveniently positioned far enough offshore to avoid the worst of the alien invaders that…are destroying New Zealand’s biodiversity.”18 This vision of an “island mainland” would make Kapiti an appropriate site for a few further introductions of species native to the forests of the Tararua Ranges across the water from it: among the birds, probably just the rifleman and the fernbird.

In Miskelly’s eyes, while Mana was a “blank canvas,” Kapiti should be treated as “an unfinished masterpiece,” where we are “constrained by the vision of the earlier artists.”19 We should respect the legacy of the early conservationists as far as possible, mindful that future generations will certainly see flaws in our concept of restoration that are currently invisible to us. He points out that there are other canvasses available where we can start restoration from scratch, but this is one place where we should work with the given history, ecological and human, and not against it. In many ways, the concept of an island mainland is a fitting emblem for New Zealand’s remarkable restoration ecology, one that has learned to be humble and confident at the same time.