A Rich & Pleasing Diversity: The Norfolk Island Rainforest

“In the patches of brush that bound the line of road which stretches from N. to south across the Island, I recognized among many plants quite new to me, several species indigenous also to New Zealand, and everywhere the golden fruits of the Lemon trees and Guava … exhibtd a rich and pleasing diversity when contrasted with the extremely beautiful dark hue of the prevailing Laurel-like foliage of the plants around them.” – Government Botanist Allan Cunningham, 1830

Around three to two million years ago a giant volcano pushed up from the ocean depths, rose above the surface and created the original Norfolk Island. This newly created, barren outcrop of rock in the middle of the western Pacific Ocean could have been ten times as large as the island is today, depending on sea level at the time. Over the following millennia the rock broke down through weathering processes, rich soils developed and the forces of nature sculptured the landscape. Plants found their way to Norfolk Island in a number of ways and, very slowly, the green mantle of vegetation began to spread across the land.

Seabirds arrived first, finding a place to rest and nest in the midst of the vast ocean. Birds can transport plant seeds amongst their feathers, stuck to their legs in mud and carried afar in their stomach to be deposited on arrival. Plants also arrived by means of the ocean currents that can carry parts of plants capable of growing great distances; this includes floating seeds, root masses and whole plants washed into the sea by floods. Weather fronts, predominantly arriving from the west in the direction of Australia and Lord Howe Island, brought tiny fern spores that found suitable niches on the moist slopes of the mountains, established themselves and spread. As the plants arrived and either flourished or perished, a succession of land birds followed, blown in front of storms from afar or losing their way from their migratory paths. Some survived and thrived on the island and can still be seen today. Occasionally reptiles arrived, clinging to floating trees; two of these eventually became established on the island. Invertebrates of all kinds came on the wind or were transported by floating debris. This process of long distance dispersal continues today, particularly of birds and insects, and occasionally a new plant arrives, unaided by humans, to become established on the island.

Many species must have arrived on the island over its long history but did not survive to the present day. Chance played a large part in which species arrived on the island, the adaptability of the species and, no doubt, luck determined which ones survived and became established and which ones died out. Imagine the probability of a rainforest tree seed from eastern Australia being transported over 1,500 kilometres of ocean to the island and then growing and reproducing to establish a sustainable population. Over such a long time period, some of the species that arrived, particularly the early arrivals, evolved into new and distinct species or forms, quite different from the original plants that found their way to the island. These are the endemic plants, plants that are restricted to Norfolk Island and therefore found nowhere else in the world.

The Norfolk Island rainforest is unique. Neither the endemic species nor the combination of plant and animal species found on the island occur anywhere else in the world. The isolation of the island in the middle of a large ocean, the latitude and the geographic location between Australia, New Zealand and the tropical islands to the north such as New Caledonia, were paramount in determining the characteristics of the rainforest that was to evolve on Norfolk Island, and that we see today. Like many islands, endemism is high; the endemic plants account for about 24 percent of the total indigenous flora.

Not surprisingly, the native plants on the island are a reflection of the floras of the closest land masses: 51 percent is shared with Australia, 33 percent with New Zealand, 21 percent with New Caledonia and 6 percent with Fiji. About 39 precent is shared with Lord Howe Island, the closest land mass, about 900kms to the southwest. The higher percentages for Australia and Lord Howe Island can be explained by the fact that the weather systems approach from the west, so that the likelihood of transport is higher from that direction.

The rainforest of Norfolk Island exhibits many of the characteristics of a subtropical rainforest. Palms are prominent, vines and creepers, including some large lianas, are common, there are fleshy-fruited species aplenty, some trees have buttressed trunks, and several species have large leaves. Epiphytes (plants that grow on trees and rocks) are common and ferns make up a large proportion of the island flora.

“we found ye Woods so very thick & so much underwood which was rendered still worse by a large kind of supple jack which formed an impenetrable net work thro’ which we had to cut our way…” – Philip Gidley King, 1788

Even the most casual observer cannot fail to notice some of the more prominent plants of the rainforest. The lofty Norfolk Island Pines are ubiquitous across the island, growing to over 50 metres on the ridges running from the mountains and towering well above the rainforest canopy. The view from the Mount Pitt lookout reveals patches of the Norfolk Island Palm and the Norfolk Island Tree Fern, reputed to be the tallest fern in the world. The variety of the plants, from small ferns and orchids to large trees, can be appreciated by a walk along one of the tracks in the National Park or the Botanic Garden.

Because of its small size and isolation, the diversity of plants (number of species) is lower than on larger land masses or on islands closer to other land. Nonetheless, there is great variety in the types of plants to be discovered. The flowers and fruits of many of the rainforest plants are small and easily over-looked, but others have quite spectacular flowers or fruits. In late summer, the large bunches of berries produced by the palm provide splashes of red against the green rainforest canopy. A relative of the Pandanas, a common sight on subtropical and tropical shores, known as Mountain Rush or Freycinettia baueriana, produces large clusters of red fruit encircled by red bracts. A most spectacular plant, it climbs high into trees using aerial roots that attach to tree trunks. Some of the vines are no less impressive. A large vine known as ‘Devil’s Guts’ clambers across the tree canopy, producing large white flowers and purple, tennis ball sized fruit. The long, rampant stems bear prickles, hence the alternative common name of ‘wait-a-while’. The large creamy-pink flower sprays of another robust vine, Callerya australis, are followed by long beans containing large orange-red seeds.

“I now come to its vegetable productions of which none are more remarkable than its Noble Pine and Fern tree, and as these are lofty plants and are naturally group’d togr. In small bodies on every part of the Island, hey form a most decided feature of the landscape.” – Allan Cunningham, 1830

Some of the plants in the rainforest are very rare, and because they only occur naturally on Norfolk Island, their conservation is a high priority. Among these plants are the Kurrajong or Wikstroemia australis, a rarely seen small tree inhabiting the ridges in the National Park, and several species of small fern. Visitors are lucky to be able to see many of the rare species that have been planted along the tracks in the National Park.

For those who wish to take a closer look at the plants, there is a tree called Bloodwood that bleeds red ‘blood’ when the bark is damaged, a tree in the stinging nettle family that does not sting, a shrub related to the plant used in the tropics for the making of the drink Kava, a wild passionfruit that produces beautiful red flowers, and a tree with the most unlikely name of Sharkwood, because of the smell of the timber.

If you do go walking in the rainforest, you will see dense thickets of small trees, usually several metres back from the walking tracks. These are Strawberry Guava and African Olive, two woody weeds and, in some ways, the worst plants introduced to Norfolk Island. The redeeming feature of the guava is that an abundance of tasty fruits are available during summer. In a campaign that will take many decades, the National Park is removing these woody weeds and allowing the native rainforest to expand. Evidence of their progress can be seen along the walking tracks, including cleared areas where few natives remain after the removal of the weed trees. You will also see rat bait stations along the tracks in the park. Rats are not native to the island and a major problem for rainforest because they eat seeds and seedlings, consume a great quantity of native invertebrates and raid bird nests.

Realising the precarious nature of some of the plant species, the local islanders have protected, propagated and planted these rare plants in various places across the island. Many of the rarer plants can be seen along the tracks through the National Park and the Botanic Garden.

The Norfolk Island rainforest, and the plants and animals it contains, is a most important and unique environmental resource, for its scientific significance and the contribution it makes to the scenic beauty of the island. Visiting the rainforest on Norfolk Island is easy and access is available for all capabilities. Short and long, well sign-posted walking tracks are provided in the National Park, and the Botanic Garden has a well-made boardwalk. When you do visit the rainforest, take a moment or two to ponder its origins and its evolution over past millennia. Today it faces its greatest threat; its future is now in our hands. Further information can be obtained from the Visitor Centre at the Botanic Garden, and excursions can be arranged through the tour companies in Burnt Pine.

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Image Credit: Robin Nisbet
www.robinnisbet.com

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Article content disclaimer: Article first published in 2899 Magazine V2 Iss2, 2010. Please note that details of specific travel, accommodation and touring options may be outdated. References to people, places and businesses, including operating days and times may be have changed. References to Government structure and Government businesses/entities may no longer be applicable. Please check directly with businesses and/or Government websites directly rather than relying on any information contained in this article before you make travel arrangements.