This spring, I toured Norfolk Island, courtesy of The Adventure Traveller. This biodiverse island occupies 35 square kilometres and is situated 1,412 km due east of Evans Head (NSW, Australia). It is a heavily eroded former volcano, 2.3 to 3 million years old, surrounded by reefs, sitting atop the Norfolk Ridge which links New Caledonia and New Zealand. It is an isolated fragment of what was once the continent of Zealandia. The Norfolk Island fauna and flora have more in common with New Zealand than Australia. Just because this is a small, fairly well explored island doesn’t mean it lacks new botanical surprises, as we were to discover.
Norfolk Island has fertile, porous soil and a mild, oceanic subtropical climate with little seasonal variation. It has some of the rarest plants on Earth, which has earned it a place as one of the Australian Government’s top twenty priority places in its Threatened Species Action Plan.
Archaeological investigation suggests that in the 13th or 14th century the island was settled by Polynesian seafarers, and there’s evidence that possibly Melanesians might also have settled on or traded with the first Norfolk Islanders. The Polynesians brought food with them – bananas, taro and Polynesian rats – which still exist on the island.
In 1788, the vegetation comprised dense subtropical rainforest with 182 native species of which 25% are endemic (that is, occurring nowhere else on Earth). Much of the land was logged, cleared for farmland and invaded by introduced farm weeds.
One consequence of this was the extinction of many endemic birds. An estimated one million providence petrels nested on Norfolk Island and they were vital for the transport of nutrients from the ocean on to the island. This bird no longer exists on Norfolk Island.
Another consequence was the change in soil hydrology. Mature Norfolk Island pines are capable of combing moisture from passing low cloud, allowing this to percolate into the soil. Land clearing has helped Norfolk island’s landscapes become drier.
As we toured, I tried to show my fellow travellers as many of these plant communities as possible so they could gain an appreciation of this surprisingly diverse, remote island.
We saw moist palm gully forest, which occurs in deep valleys on the mountains Mt Pitt and Mt Bates within the Norfolk Island National Park. It has dense stands of endemic tree ferns and Rhopalostylis baueri, the fruit of the latter being a major food of the endangered endemic green parrot.
Moist upland hardwood forest, which is dense and diverse and also mostly within Norfolk Island National Park. It occurs on valley slopes between the moist palm gully forest and the mountain ridges. We spotted Ungeria floribunda and the ancient fern, Tmesipteris norfolkiana, and Thelychiton brachypus in bloom.
Pine-hardwood ridge forest is probably the most threatened plant community of all. There are many Norfolk Island pines, unlike the moist upland hardwood forest, and the pine seed is an important seasonal food for the green parrot.
When our boat tour of Phillip Island was cancelled due to rough seas, I organised for us to take the summit walking track between Mt Pitt and Mt Bates. We spotted two species of epiphytic orchid, Thelychiton macropus and Taeniophyllum norfolkianum, both in bloom.
We passed through a regenerating patch of viny hardwood forest when we visited Ria’s open garden (11.10.22). The Samson’s sinews, Callerya australis, was a stand out climber in that thick, moist, lowland rainforest under white oak, Celtis paniculata, trees.
On the same day we visited some plateau hardwood forest – revegetated patch of forest that had been logged and used for making charcoal. This plant community is drier and contains Norfolk Island hibiscus, Lagunaria patersonii, but the patch we saw was species poor and lacking in epiphytes.
We strolled through several plant communities on one walk through 100 Acres Wood on 12.10.22. First was a patch of revegetated lowland valley hardwood forest. Once widespread, there are many Lagunaria patersonii trees and also signs the birdcatcher tree, Pisonia brunoniana, and Cyathea brownii, are increasing in number.
As we headed towards the cliffs, we passed through coastal pine and white oak forest and then into white oak shrubland. The shrubland community once occurred along the entire coast around the island, and on Nepean Island. The understory of both communities is quite open and, being close to the cliffs, is frequently tunnelled by nesting birds.
At Emily Bay we saw a patch of sandy beach herbland with thick, low-growing perennials tolerant of salt water, including pig face, Carpobrotus glaucescens, Ipomoea pes-caprae, Vigna marina and salt couch, Sporobolus virginicus.
Towards the Captain Cook Memorial, we saw patches of coastal flax (Phormium tenax) community. This community is still speculative as little evidence remains of its original character and distribution. Although coastal flax was present by the time of the arrival of Cook in 1774, it is not certain that flax was present on Norfolk Island prior to the arrival of the first settlers in the 13th and 14th century. The first settlers may have introduced this useful plant.
We did not see moo-oo sedgeland (Cyperus lucidus). While common on Phillip Island, only remnants occur on Norfolk Island’s northern coast. We glimpsed a few areas of freshwater swamp from the coach on our travels without stopping. In many places, logging sloping land caused the loose soil to slump, filling swampland in gulleys, and more swampland was filled to make way for the airport.
In all, we managed to see half of the native plant species. Members of our group found new locations for existing threatened species, and possibly two new species as yet unrecorded by science.
What were the new botanical surprises? A new location for an orchid, and that orchid might also be a new species for this island.
Best of all was a plant discovery that might mean Norfolk Island may have a new genus. Since you can’t manage what you can’t measure (a Dr David Suzuki saying) this new species and the plants (and animals?) with which is cohabits will add further complexity to the National Recovery Plan for Norfolk Island.
My thanks to Devin Hunt of The Adventure Traveller for organising this busman’s holiday. I’ll wager he didn’t expect this trip would to push back the boundaries of science 🙂
2nd November 2022
Director, Seed Savers Network
Patron, National Toxics Network
Patron, Householder’s Options to Protect the Environment