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New Zealand Conservation: The Absence and Presence of Terrestrial Mammals

Written by Adam Dillon, 2015-2016 Sustainability Leadership Fellow and PhD Candidate in the Department of Fish, Wildlife and Conservation Biology.

Arriving in New Zealand for the first time, I was captivated by the beauty and uniqueness of the country. The diversity of landscapes in a country the size of Colorado was stunning, from coastal mangrove forests and secluded white sandy beaches to powerfully active volcanoes and dramatic fiords. Not only were the landscapes spectacular but the plants and animals were incredibly unique, with approximately 70% of its birds, 80% of its plants, and 100% of its reptiles and amphibians being found nowhere else on Earth. Although many people are aware of New Zealand’s iconic kiwi bird, fewer people realize that its home to the heaviest insect in the world (giant weta), the only true alpine parrot (kea), and a reptile that is older than most dinosaurs (tuatara). At one time New Zealand was home to the tallest bird that ever lived, the giant moa, and the largest bird of prey that’s ever existed, the Haast Eagle. But unfortunately they, like many other endemic species, have gone extinct.

 

As for any new traveler to New Zealand’s wilderness, I started to ask myself two ecological questions. What is it about New Zealand that makes it home to such unique species? And why have so many of these species gone extinct in recent time? The answer to both of these questions can be summarized in a single word: mammals. The absence of terrestrial mammals aided the creation of such unique species but the introduction of such mammals is now responsible for their recent extinction.

Approximately 80 million years ago, prior to the Age of Mammals, the land that became New Zealand broke apart from the supercontinent Gondwana. This means the animals that evolved in New Zealand did so in the absence of terrestrial mammals for at least 15 million years, possibly much longer! Their absence allowed birds, reptiles, and insects to evolve into niches often held by mammals (i.e. giant moa functioned much like grazing mammals). But New Zealand’s greatest blessing is also its greatest curse. Because its flora and fauna didn’t evolve alongside mammals, these unlikely creatures have no defense against predators they’ve never seen before.

The first of all terrestrial mammals to arrive in New Zealand was man, Polynesians to be exact. Upon their arrival in the 13th century, 32 bird species went extinct, and another 9 species followed after the arrival of Europeans in the late 18th century. Many species were driven to extinction from overharvesting, while others were driven there by predation from introduced predators. New Zealand currently harbors 28 species of said mammals including herbivores like deer and elk, omnivores like rats and possums, and predators like stoats and cats. But there’s a silver lining, of sorts: knowing the problem can lead to possible solutions. New Zealand is a country that comprises 2 main islands and well over 100 smaller offshore islands. Over the past couple of decades, the New Zealand Department of Conservation (DOC) has made non-native mammal eradication and native restoration on these offshore islands a main priority. The first step is the removal of all non-native mammals usually through trapping and poison. Once an island is free of pests, rare endemics can be reintroduced. This approach has been extremely successful, with currently more than 100 “pest-free” islands and many populations of rare birds returning, including the takahe, saddleback, and kiwi.

Although offshore island restoration has been successful, the number of available islands is becoming smaller and smaller, plus it does nothing for the mainland populations. For these reasons and others, additional conservation measures are being implemented through “mainland islands”. One type of “mainland island” is a plot of native bush surrounded by a predator-proof fence, within which invasive mammals are eradicated. However, these areas are relatively small and extremely expensive to maintain. The second type of “mainland island” is a large area of native bush that’s intensively trapped in order to control nonnative mammals. Rare species can then be released to recover. Although some mainland island trapping programs are conducted by DOC, hundreds more are maintained by passionate local communities with great success.

For the past 6 years I’ve been fortunate enough to travel to New Zealand once a year, as an instructor with an environmental education program called Wildlands Studies. About a dozen of my students and I volunteer with organizations conducting conservation field work. We have worked on a mainland island project with an organization called Friends of Flora (FoF) in the diverse, low altitude mountains of Kahurangi National Park ever since the class began 6 years ago. Through the years we laid out and maintained trapping lines and also witnessed populations of rare kiwis and blue ducks recovering. This past year we also volunteered in the beautifully lush rainforests of Fiordlands National Park with junior-high and high-school aged kids from the Kids Restore the Kepler program. The Kids Restore the Kepler program is a joint project between the Fiordlands Conservation Trust and DOC that has both conservation and education goals. The project aims to restore native birds to the area and help Fiordland’s next generation of citizens, from pre-school through high-school, develop knowledge, values and skills so they can be confident, connected, and actively involved in caring for their environment.

Despite New Zealand’s native flora and fauna facing a major threat from invasive mammals, and despite the many difficult challenges that lay ahead for New Zealand conservation, it has been inspiring and uplifting to bear witness to passionate community-run conservation organizations tackling the tough challenges of native species decline, and providing solutions and hope for the future of New Zealand’s wildlife.

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