Delicate ecosystems - and a unique mixture of natural and human history - need intelligent management and support from everyone
The lovely islands of the Hauraki Gulf are so familiar to most of us that it is a surprise to learn so much from the closer look we have taken at some of them this week. How many knew, for example, that Kawau is suffering so much from the predations of wallabies introduced by Governor Grey? Or that weka are causing such tensions between residents who suspect their neighbours are transferring the birds to their gardens?
Who knew how rats are tracked and killed on Motuihe, and how successful that effort has been despite the numbers of boats, campers and day-trippers the island attracts?
Who knew a stoat could swim at all, let alone the 3km it must have swum to reach Motutapu after a successful eradication programme?
Just about everyone surely does know about the native birdlife that has been restored to Tiritiri Matangi by a determined pest eradication.
But not many knew that tieke (saddleback) are now surviving on Motutapu too, and that four takahe have been released there.
Islands have a special place in the human imagination and offer the best prospects of reviving the birdlife that once flourished in New Zealand. It would be a pity if islands had to be closed to human life, like Little Barrier. If we treat all the Gulf islands extra carefully when we set foot on them, we might all enjoy the birdsong that ought to be everywhere.
Taking extra care probably means leaving the pets at home. Roaming dogs do not give flightless birds a chance. One dog could decimate the 40 kiwi on Motuihe, said John Laurence, chairman of the Motuihe trust, and the island ranger John Mills added that kiwi have a particular attraction. "They exude something that drives dogs crazy."
Despite warnings on VHF radio and signs on the island, he said, boat owners often brought their dogs ashore. Mr Mills used to give offenders another warning. Now he spot-fines them $400. And if their dog is found on the island again it is impounded. Possibly it requires poison to be laid before some people will be persuaded to keep their pets away.
No matter how much care people take, they may be accompanied by unwanted scavengers. Considering the number of boats at anchor and the camping permitted by the Department of Conservation, it is remarkable that only one rat has been seen on Motuihe in the past five years. They can do more damage than dogs, climbing trees to attack birds and consume nests of eggs.
The department needs to strike a difficult balance between the interests of endangered species and human access to the islands. In some places, such as Kawau, it needs to conserve a human heritage as well as nature. Residents have been rightly critical of the maintenance of Grey's mansion and an old copper mine pumphouse.
An "Eden" of introduced wallabies and peacocks, like mineral extraction, might not be approved uses of an island today but activities such as those hold an abiding interest for visitors. The department is meeting that need by repairing the mansion roof and building a wall to protect the mine pumphouse from further wave damage.
On other islands, where the natural heritage can be protected, all who visit them should exercise care and help keep them open sanctuaries, safe for native species and our pleasure.