A speck in the ocean
On the ocean floor a volcanic vent erupted, red-hot liquid basalt boiling the water above and solidifying. Repeatedly liquid rock poured out of the vent, building a mound which eventually reached the ocean’s surface. An island was born. The volcanic activity continued with sporadic eruptions. Erosion between the eruptions wore parts away, only to be replaced by new material. The island grew. About two million years ago, volcanic activity ended. This island, Norfolk Island, was not alone — ten others had been created nearby in similar fashion, just one of which (Phillip Island) remains above sea level. These two surviving islands have each lost roughly two-thirds of their original size to erosion.
These islands are perched atop a much older volcanic plateau which rises to about 75 metres below the present sea level. Since the islands were created, at about 100,000-year intervals, global ice ages bound water in ice, lowering sea level by as much as 140 metres. Each time, our two present islands and the other nine volcanoes became part of a single, much larger, island. This large island of the ice ages was about one hundred times the size of the two little islands we can visit now. That last applied about 13,000 years ago.
Plants, especially those growing from spores such as mosses and ferns, began colonising the new land surfaces whenever they were cool enough, between eruptions. Subsequent eruptions destroyed all or most of them. When the eruptions ended, development of permanent vegetation began. We cannot know what grew there before written records began but we can be sure many species established and later died out.
Increasing an island’s size by a factor of ten roughly doubles the number of species it can accommodate. So when the island was one hundred times its present size it could accommodate four times as many species. Then three-quarters of the species would become extinct there each time the sea rose to the present level between ice ages.
The loss of plant and animal species would have been greatest when ice ages were ending and the rising ocean shrank the islands, but new arrivals would displace some species already present. Many species vanished from the islands without trace.
With the most recent return of sea level — about 6,000 years ago — to what we know (and wrongly consider normal) the islands reached their present size and geography. Arrival of plants and fauna continued, some replacing others to develop the complement of species which is known and documented. A substantial proportion of the species evolved on Norfolk to become new, endemic, species. For example, 45 of the 182 native plant species occur nowhere else.
Humans first arrived here about 800 years ago. These were Polynesian migrants who possibly came and left several times during the next 200 years. Archaeological investigations have shown the migrants probably came from eastern Polynesia but also had links to New Zealand. They established a small settlement similar to equivalent structures of eastern Polynesia at that time. Polynesians brought obsidian, or volcanic glass, valuable for making tools, from the Kermadec Islands 1400 km east of Norfolk. The Polynesians had a substantial impact on the flora and fauna of Norfolk Island, some of which is revealed by fossils. Birds, particularly seabirds, were important food for these people. Significantly the Polynesians brought Pacific rats (Rattus exulans) and some useful plants.
The rats are vigorous predators and probably caused extinction of several species of small birds, and also seabirds and snipe known from fossils here but not known to have survived beyond the Polynesian period. Pacific rats probably also killed out the two lizard species and a large centipede which still occur on Phillip Island, which does not have rats. The rats also probably eliminated some plant species known from Phillip Island but not on Norfolk Island.
By about 600 years ago, the Polynesians had left but their rats remained. Apparently no-one visited the island again until 1774 when renowned navigator and explorer James Cook and his ship, the Resolution, chanced to find the island, naming it “Norfolk”. A small group spent several hours ashore, enabling the first documentation of the island’s flora and fauna. The visitors were impressed with the New Zealand Flax (Phormium tenax) and the Norfolk Island Pines (Araucaria heterophylla) which appeared valuable for ships’ masts. The palms (Rhopalostylis baueri) and numerous birds provided the ship’s crew with very welcome fresh food.
Cook’s favourable report led the British government to establish a small settlement on Norfolk Island in March 1788, six weeks after colonising Australia. Soon the Pacific rats were seriously damaging the settlers’ vital vegetable gardens, causing great disappointment. A month later, plantain or bananas were found, evidence of earlier Polynesian presence on the island.
Soon after the first twenty-three colonists including fifteen convicts arrived, the food value of the wild birds and plants of Norfolk Island was recorded in an official document. Within a year of settlement the slaughter of birds for food had already had substantial impact. The colony on Norfolk Island developed quickly, with periodic groups of new arrivals, mostly convicts, shipped from Sydney. By 1794 about half the area of the island was allocated to individuals. But before reaching that point the infant colony nearly failed catastrophically.
In 1790 HMS Sirius, flag ship of the fleet which brought the British to Australia and Norfolk Island, foundered on Norfolk Island’s reef. The loss of the Sirius left the colonies with only one tiny ship when importing food from India or South Africa was necessary to feed the people. The situation on Norfolk Island was critical.
The stranded crew of the Sirius and new arrivals had trebled the population to more than 500. The island’s food production was grossly inadequate. With no external contact, very strict rationing was imposed. Despite fishing whenever possible, the food supply fell far short of the minimum needed.
Then flocks of a seabird species (Pterodroma solandri) returned to the island to breed. These birds became critical to survival of the colonists. Nightly expeditions, using flaming torches, visited Mount Pitt where the birds could be caught and eggs collected. A tally of birds killed showed nightly numbers were often in the thousands, sometimes more than 5000, amounting to about 200,000 birds and countless eggs. The birds’ value in sustaining the beleaguered population earned them the name Birds of Providence. In addition, the desperate people harvested other birds while the palms were also harvested intensively until almost wiped out.
The natural foods of the island were exhausted and remaining rations sufficient for only a few days more when at last two ships arrived, ending five months of isolation and constant hunger and desperation.
Within ten years, the Birds of Providence were gone and they were believed extinct. The endemic Norfolk Island Ground Dove, also easy to catch and good to eat, was last recorded in 1800. A large endemic parrot soon followed these to extinction.
In 1793 pigs were released on Phillip Island to provide a fresh food resource for the people on Norfolk Island. The pigs thrived and their numbers rapidly grew.
The colony on Norfolk Island was abandoned in 1814, with some livestock left to fend for themselves. By then much of the forest had been cleared. On Phillip Island the pigs fed and bred unchecked.
A new settlement began in 1825, but this outpost was a harsh penal colony, described as the severest form of punishment short of death. Some convicts suffered so badly they preferred death rather than life on Norfolk. Sometimes convicts committed crimes on Norfolk hoping to induce their own execution, to end an intolerable life.
Goats and rabbits were released on Phillip Island early in this settlement. Together with the pigs they had a devastating impact on the island, destroying the vegetation, leading to severe erosion. The island would become a spectacular example of the damage which feral animals could cause.
After the famous mutiny on the Bounty, the lead mutineer Fletcher Christian and eight of his comrades chose Pitcairn Island for their refuge from the authorities. A few other men later joined the Pitcairn community. By 1855 the population there exceeded the island’s capacity for food production and many were starving, prompting the British government to move the islanders to Norfolk. The penal colony had recently been abandoned.
The Norfolk Island community is still largely made up of the descendants of the people from Pitcairn. The names of some of the mutineers and the later additions to the Pitcairn community dominate the Norfolk Island telephone directory which, to avoid confusion, lists many islanders by their nicknames.
A national park was established in 1984, encompassing the Mount Pitt Reserve and Phillip Island. The two components were dramatically different. The area on Norfolk Island, despite being severely weed-infested, contained most of the remaining good-quality native vegetation with some beautiful subtropical rainforest and the main or only habitat of many of the threatened plant and animal species. In contrast, Phillip Island was spectacularly degraded after a century of severe erosion. The landscape lacked vegetation and soil, revealing the underlying geological structure.
Eradication of the last grazers, European rabbits, on Phillip Island began in 1978. The extremely rugged terrain, with cliffs up to 250 metres high, made rabbit eradication difficult and hazardous but by 1986 the island was free from grazing. Even before the rabbits were completely eliminated, plant species not seen there before, or not recorded there for more than 150 years, began appearing. A single individual of a previously unknown shrubby tree species was found. That sole specimen produced seed from which all known representatives of the species are derived. No living person had seen another plant, Abutilon julianae, before. It had been considered extinct for seventy years and not recorded on Phillip Island since 1804. With revegetation of Phillip Island the diversity of birds there increased. Twice as many species were recorded in 2005 as in a similar survey before rabbit eradication began.
Since exclusion of cattle from the former Mount Pitt Reserve, regeneration of native plants has been successful. But the island still has some of the world’s rarest plants. The Phillip Island Glory Pea (Streblorrhiza speciosa) has long been extinct, an early victim of the feral animals. The Phillip Island Hibiscus (Hibiscus insularis), which occurs naturally only on that island, has just a single wild individual, which appears to be several plants due to suckering. Eleven Norfolk Island plant species had fewer than fifty mature individuals in 2003 while another nineteen had less than 200.
Sadly Norfolk Island’s birds have fared even worse. Seven endemic bird species or sub-species have become extinct since 1788. Others, known only from fossils, are extinct or at least extinct here.
The Norfolk Island owl, Ninox novaeseelandiae undulata, declined to just a single female bird in 1986. In a desperate attempt to preserve her genes, two closely related New Zealand male owls were released on the island. A clutch of young resulted. With careful management the young hybrid owls survived and produced further young. Now the nocturnal call of owls can be heard anywhere on Norfolk Island.
Another Norfolk Island species which became one of the world’s rarest birds, with only three to five breeding pairs in the 1970s, is the endemic Green Parrot Cyanoramphus cookii. Intensive effort has increased the population substantially. For both the owl and the green parrot, control of introduced parrots (which compete for nest sites), rats and feral cats was supplemented by provision of nest boxes designed to prevent predation.
Plants and animals continue to arrive naturally. During the last forty years several plant species have arrived and established, mainly those with tiny, windblown, seeds or spores but also species with seeds carried by birds. In that period several species of land birds have also arrived and established, as have some seabird species. A five-year survey of moths on Norfolk Island revealed that a large number of the recorded species were not resident but had travelled long distances, mainly from Australia, 1400 km away. That so many species have arrived on this isolated island in a short period suggests that the flora and fauna must have changed immensely during the two million years since volcanic islandbuilding ended. The islands’ complement of species is always changing.
People, too, have brought plants and animals to the island with substantial impact on the native species. Polynesians brought the Pacific Rat about 800 years ago but the even more damaging Black Rat (Rattus rattus) arrived during the Second World War. Rats have serious impacts on fauna and some plant species. People have introduced numerous aggressive weed species, greatly changing the island’s vegetation.
During the last half century, nature conservation efforts at Norfolk Island have greatly improved the environmental outlook. Many threatened plants have been propagated and planted widely, including in private gardens. Establishment of the National Park enabled management for conservation. Environmental awareness on the island has improved greatly. The environmental future of Norfolk Island and its tiny neighbour Phillip Island now looks promising.
