Wallabies have chewed away most of the undergrowth, and imported pine trees dominate Kawau's forest. A small population of kiwi survive, and weka are plentiful, but the many dogs, cats, rats and wallabies on the island mean it is not the Eden that Grey envisaged.
Therefore the conservation strategy on the island is selective. The frugal Department of Conservation, which owns a tenth of Kawau's land, focuses mostly on historical conservation, not species conservation.
DoC oversees the historic reserve at the southern end of the island and the structures within this area, in particular Grey's 19th-century mansion and a 157-year-old engine house from the defunct copper mine.
There is tension between the residents and the department over the gradual decay of these two tourism attractions. The mansion at the head of Mansion House Bay has become shabby, its roof weather-beaten, and parts of the copper mine pumphouse have begun falling into the sea.
The editor of the island's Kookaburra magazine, Michael Marris, said homeowners were concerned that the Government had given up on the island's architectural heritage.
"It seems some people in Wellington felt that getting rid of every bit of our colonial history would not be a bad idea."
That history is probably the richest of any of the Hauraki Gulf islands. Before copper ore miners and Governor Grey inhabited Kawau, Maori raiding parties used the 2000ha island as a base. Their occupation ended when tribes from the mainland attacked, killed and ate some of them.
As a result, an ancient grove of puriri at Bostaquet Bay is known as the "cannibal feasting hall".
In the 1860s, Grey spent his fortune on Kawau. His eccentric vision for the place included a zebra-drawn cart and plants shipped from Europe and the Americas. His taste for exotic flora and fauna remains in the Brazilian palms at Mansion House Bay, and the peacocks which stalk the grounds.
This summer DoC responded to residents' badgering with moves to ensure the island's architectural history is kept intact.
The mine's pumphouse, a slim, sandstone structure on the island's south-western end, has been battered by 160 years of waves and wind.
One of the first industrial buildings in New Zealand, it is a relic of early industry and the fierce competition for lucrative minerals. One of the main reasons for its closure in 1855 was flooding caused by a rival mining company which tried to dig into the original mine from the high-tide mark.
At a cost of $229,000, the sea-facing wall is being bolstered and another wall will be built near the high-tide mark to take the force out of the waves.
The proposed mansion clean-up should be easier. DoC ranger Shane McInnes said that in March the sprawling two-storey colonial building would have its roof repaired and most of the exterior would get a new coat of paint.
Tension between islanders and mainland decision-makers is likely to remain after DoC's clean-up efforts, because the residents crave independence from bureaucracy, but depend on government bodies to keep the infrastructure from decay. Without DoC's tourist attractions the island would probably not have a ferry service.
Mr Marris portrays the Kawau life as a romantic one where residents relish the lack of roads and lawnmowers, where affluent homeowners relate well to "the more feral islanders" and morning conversations take place over dinghies, not fences.
He also admits that despite his community's desire for a Republic of Kawau, their worries are small.
"When you look at the global picture - all the problems - our worst complaints are about wallabies. So that's not too bad."
GULF PARADISE
Today: Kawau Island
Tomorrow: Motuihe Island
Wednesday: Motutapu Island
Thursday: Little Barrier Island and Burgess Island
Friday: Motiti Island.
