We often forget the role that healthy native forest plays in the health and diversity of our native birds, reptiles and insects. All are dependent on the plants, either as their primary food source, such as nectar (tui, hihi) or foliage (kokako, kakapo) or as a secondary food source, where they feed on creatures such as insects that feed on the plants (fantails, bats) or as carnivores eating bird or reptile species (morepork). The streams and fish life also benefit from a healthy forest system that provides shade and food sources, filters the water and slows the run-off.
On Hauturu we have a prime example of a healthy forest ecosystem with around two-thirds of the island evolving undisturbed from ancient primeval forest and the remaining third naturally regenerating now for 120 years. There are 428 known species of native vascular plants on Hauturu. The island also has a wealth of mosses, lichens, liverworts and fungi. Due to the ruggedness and inaccessibility of the island, it is possible that there are yet undiscovered species present. The range and variety of plant species means there is always something in fruit or flower. I was there once in mid-winter doing kiwi monitoring and didn’t think there was much for the birds to eat so I started taking photos of each species that had either fruit or flowers present. When I got to 50 different species I decided there was enough!
The island rises from sea level to 722-metres going from almost sub-tropical forest, containing northern coastal species such as parapara (bird-catcher) and pohutukawa, to sub-alpine cloud forest featuring plants more commonly found in cooler southern latitudes, such as southern rata and mistletoe. The vegetation on Hauturu is surprisingly different from neighbouring Great Barrier Island, Aotea. Hauturu has only small numbers of podocarps, such as kahikatea, no ordinary cabbage trees, very few kowhai or kumarahou.
There is, however, a wonderful kauri/hard beech forest. Another unusual feature is many epiphytes normally found up in the trees are often seen growing on the ground as well, probably due to the lack of browsing animals. The understory is rich in ferns, grasses creepers and seedlings.
Hauturu is lucky to have few of the invasive plant species that encroach on mainland forests, the main threats come from pampas grass and climbing asparagus. Over the years, through the generosity of funding organisations such as Foundation North, Chisholm Whitney Family Trust and DOC’s Community Conservation Fund, the Hauturu Supporters Trust has been able to provide sufficient funds for helicopter spraying and abseilers to deal with weeds on cliffs and slip faces, as well as funds towards weed team workers. The aim of the Trust is to assist DOC and iwi partners to protect and preserve the rich native habitat of this jewel into the future.
The black petrel team has been on the island putting out sound recorders and checking burrows. The NZ storm petrel team has also been on the island checking numbers and this year’s breeding activity of these tiny birds. The Little Barrier Island/Hauturu Supporters Trust has been working with NHNZ, formerly Natural History NZ, on producing a short video on the rich diversity of the island. We hope this will be publicly available at no cost after the launch next month.