1226th Ordinary General Meeting

"Australia's most spectacular environmental rehabilitation project: Phillip Island, Pacific Ocean"

Dr Peter Coyn

Date: Wednesday, 1 October 2014

Perched atop a submerged seamount, in turn atop a submarine ridge, Phillip Island and its close neighbour Norfolk Island are tiny specks, the only land in a vast expanse (2.5 million square kilometres) of the southwest Pacific Ocean. Both islands were created by volcanic activity between 2.8 and 2.2 million years ago. The plateau top of the seamount, 100 x 35 kilometres, is between 30 and 75 metres below present sea level. Sequential ice ages during the last 2 million years exposed the entire plateau, an area about 100 times the size of the present islands. Such an area could have accommodated about four times as many species as the present islands. During the last ice age the entire plateau was exposed for 24,000 years until 13,000 years ago. Sea level 25 metres higher, reached 10,000 years ago, still exposed an island about 35 km long, large enough to accommodate more than double the species count of the present islands and joining these islands with dry land. An island at least this large was exposed for 60,000 years during the last ice age, before the sea reached its present level just 6,000 years ago. The generally much larger size of the islands and the ecological stress caused by their declining area, and the consequent loss of three-quarters of their species, between 13,000 and 6,000 years ago, could help explain the great biological value of the islands and Phillip Island specifically.

Phillip Island was densely vegetated when pigs were released there in 1793, followed by goats and rabbits by 1830. The feral grazers quickly destroyed the vegetation and by 1860 the island was mostly bare. Photographs dated 1906, when only rabbits remained, show landscapes almost identical to those of 1980 — almost no vegetation was present. In 1979 Dr Coyne began a three-year experimental program to investigate the effects of the rabbits and potential for vegetation re-establishment. The work was physically difficult and often hazardous. The first year's results were enough to persuade decision-makers the rabbits should be eradicated. That work began in 1981 and by 1986 the rabbits had been destroyed by a combination of an artificial strain of myxoma virus, poisoning, shooting, trapping and fumigating. The eradication program required swimming to habitat accessible only from the sea, archery to distribute the myxoma vector (rabbit fleas) to other inaccessible areas of habitat, and a lot of rock climbing on cliffs to 250 metres high. Since then the island has been transformed by new vegetation, most arising spontaneously. Some of the world's rarest plant species have been discovered, rediscovered or have increased in numbers. One has only a single genotype, two have fewer than fifty individuals and another has fewer than 250 individuals. A genus and species endemic to Phillip Island sadly was not rediscovered and at least two Phillip Island plants are extinct. Fauna have also benefitted from the revegetation, and being free of rats and cats the island has potential as a refuge for threatened fauna endemic to Norfolk Island.

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