Three of our botanists recently spent a week on Norfolk Island collecting ferns with colleagues from the Royal Botanic Gardens Victoria. Our fern findings will be detailed in a future blog post but here we discuss interesting flowering plants that we saw – some of which were very familiar to us as New Zealanders but others were completely new!
Norfolk Island is around 625 km northwest of New Zealand, about halfway between New Zealand and New Caledonia. It is a small island measuring only about 8 km by 5km.
Along with two even smaller nearby islands, Phillip and Nepean, it forms the Territory of Norfolk Island.
Norfolk Island is the remains of an old volcano that started erupting around 3 million years ago but has been dormant for the last 2 million years.
Some things exist in isolation
The isolated position of these islands means that the approximately 180 native vascular plant species arrived by dispersal. Consequently, the plants have affinities to the floras of surrounding land masses, particularly New Zealand, New Caledonia, and Australia. But there has been sufficient time for new species to evolve: 46 plant species are endemic to Norfolk Island (found nowhere else).
Much of Norfolk Island has been cleared for agriculture with only around 15% of the land protected in reserves. Norfolk Island National Park is the largest reserve and it encompasses the higher elevation parts of the island, including Mount Bates, the highest point at 319 m. The National Park also has the most intact indigenous forest and was where we spent most of our time.
The Territory of Norfolk Island has many threatened plant species. In 2003, 11 species were known from fewer than 50 mature plants! Propagation has since increased the numbers of these plants but 46 plant species, including 31 endemics, remain threatened. This is approximately 40% of the native plants on the islands.
Known by any other name
Over the course of our week-long fieldtrip, we saw many of Norfolk Island’s plant species. A number of species are shared with New Zealand, although some of the Norfolk Island plants have been classified as different subspecies.
A number of plants on Norfolk Island have similar-looking relatives in New Zealand but belong to different species. For many of these, we could determine the genus because they looked so similar to New Zealand species with which we are familiar.
The very different
Several other species that we saw looked quite different to any native New Zealand species.
Introduced weeds are a major threat to the native flora of Norfolk Island. There are almost twice as many introduced species as indigenous species!
Other common and widespread weeds were African olive (Olea europaea), lantana (Lantana camara) and Brazilian pepper (Schinus terebinthifolius). All three are also on the list of the world’s 100 worst invasive species.
We’re not innocent
There are also several weeds from New Zealand. For example, Kermadec pōhutukawa (Metrosideros kermadecensis) has been planted as shelter belts but has escaped cultivation. We saw it established at several areas around the coast. It is also a weed in Hawaii.
Harakeke (Phormium tenax) is another New Zealand species that occurs on Norfolk Island, where it is known as flax. The origins of this species, as well as its influence on early European settlement of the island, will be covered in another blog post.