Kapiti Island – an environmental history “microcosm” – Part 2

In 1870, Kapiti was identified by naturalists as a possible site for a bird sanctuary. But it was over a quarter of a century before the Kapiti Island Public Reserve Act (1897) was passed, and the island became a reserve.

Remnant forest, scrubland and previously farmed land was left to regenerate (except for one remaining farm at Waiorua, which continued to be farmed until the 1950s). However, nothing was done to eradicate the introduced species – cattle, goats, sheep, and possums (which had been introduced in 1893 – only four years before Kapiti became a reserve), and these animals kept regeneration of the forest in check through their constant browsing.

In 1907, botanist Dr Leonard Cockayne (1855 – 1934) was commissioned by the government to do a botanical survey. Cockayne also set out what would need to be done in order for the island to function as a sanctuary for birds and plants. Among his recommendations were that all introduced animals should be destroyed, including possums – despite there being little evidence at the time that they caused any damage to vegetation. The government accepted his recommendations and from that point on, the island’s caretakers were encouraged to shoot wild cattle, sheep, cats, goats and other exotic species. Given Kapiti’s rugged topography – including potentially treacherous ridges and cliffs – this was by no means an easy task, particularly in the case of the skilled climber, the goat. But J.L. Bennett, who was a caretaker during the 1910s and up to his death in 1924, was undaunted by the challenging task of eradicating goats, and even took to his dinghy, shooting them from the sea.

Bennett was also instrumental in alerting the government to the damage that possums caused to indigenous vegetation – an effect virtually unknown at that time. He made detailed accounts of his careful observations of the possum and its impacts and submitted these to the Lands and Survey Department. On the basis of these reports, the government changed its policy to refuse applications to liberate possums around the country, something considered acceptable practice until that time.

Bennett’s successor, Stan Wilkinson, was equally passionate about his work. In 1930, all goats, sheep and wild cattle had been eradicated, and he set about planting trees.  Throughout the 1930s, thousands of trees (not all of them native to the island) were planted each year by Wilkinson, along with his friends and plant enthusiasts from around the country.

Possums had not yet been eradicated however, and it has been estimated that the island’s marsupial population was chewing through 14 tonnes of plant material each night. This was not only inhibiting the regeneration of many species (and therefore affecting the reproduction of birds that feed on them), it was causing the virtual extermination of some species, such as the fuchsia.  Between 1982 and 1986, a small but determined group of trappers eliminated every last possum from Kapiti.

Finally, in 1996, rats (both kiore and Norway rats), which had also inhibited regeneration by their browsing of flowers, fruits and seeds, were eradicated using aerial application of brodifacoum, leaving the island completely free of introduced mammals.

The island is now one of New Zealand’s most important sites for bird recovery. Stitchbird, kokako, takahe, brown teal, and saddleback have all been transferred to Kapiti since the 1980s. The little spotted kiwi thrives on Kapiti Island but is now extinct on the mainland. Species such as kakariki (red-crowned parakeet), robin, bellbird and saddleback, have all increased since the eradication of rats.

See also Part 1 of the Kapiti Island envirohistory

Photo: a North Island kokako, one of the endangered bird species on Kapiti Island. (Photo by Matt Binns).

To hear a recording of the haunting song of the kokako, click here and start the player on the right-hand side of the page.

[Sources: Department of Conservation, Kapiti (1999), by Chris Maclean.]

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