Kawau plays key role in global study

Dr James Russell with a grey-faced petrel chick, which could return to Kawau Island following pest eradication.

A major global study has found that Kawau Island could play a pivotal role in helping to save some of the world’s most endangered species.

A team of international researchers found that if predatory mammals could be eradicated from 107 islands around the planet, it would protect 80 threatened species and help reach a United Nations Environmental Programme goal to halt biodiversity loss.

Five of the islands are in New Zealand. They are Kawau, Great Barrier, Motukawanui, Slipper and Auckland Island.

The study said predatory mammals that would need to be eliminated on Kawau to protect threatened species included cats, mice, stoats, rats and possums.

Threatened species already living on the island that would be protected by the elimination of predators include kiwis.

However, University of Auckland conservation biologist Dr James Russell, who contributed to the study, says a predator-free Kawau could become a haven for many other threatened species that don’t currently live on the island, but could be located there should they prove difficult or impossible to protect elsewhere.    

Examples from around the Hauraki Gulf include birds such as saddleback, kokako, whitehead, kakariki, robin and numerous seabird species such as burrowing petrels. Reptiles such as skinks, geckos and tuatara could also be protected on Kawau.  

“The list could go on,” Dr Russell says.

He says Kawau is a good choice for eradication efforts because of its size and New Zealand’s success in eradicating predators on other islands.

Because the study focused on eradicating predatory mammals, it did not mention wallabies, which were introduced to Kawau by former Governor of New Zealand Sir George Grey around 1870.

Although not predatory, wallabies have been blamed for destroying native bush and associated birdlife – though some islanders value them as part of the island’s history and as an attraction for visitors.

Dr Russell says if there is to be a “holistic ecological restoration” of Kawau, then a discussion needs to be had over the management of wallabies, which considers both biodiversity and the cultural values of the island.

He also advocates for wider community discussion on eradication initiatives, including the merits of different approaches, such as whether poison or traps are used, and the social side effects of eradication, such as the effect of increasing bird numbers.     

Dr Russell acknowledges that being an inhabited island, Kawau presents challenges since predators could be introduced on boats docking at the island, though he believes this problem is not insurmountable

“Other islands, for example Islington Bay and Great Mercury, are maintained rat-free with dozens of boats visiting a day,” he says.

Pet cats should not be a problem if they are desexed and not roaming outside properties. Dr Russell says it’s unlikely everyone will get onside with an eradication programme, but this has not stopped vaccination programmes or water fluoridation programmes.

“I think eradication could happen quite quickly, and it would benefit not just wildlife, but also humans – no more rodents spreading disease or invading houses when owners are away.”      

Elimination of predators on Kawau is already part of Auckland Council’s Regional Pest Management Plan 2019-2029. Council aims to eliminate rats, stoats, possums and wallabies from the island over the next 10 years through various methods, including extermination, monitoring and landowner education. 

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