298 mature individuals
Restricted to Little Mangere Island for over 80 years, the deteriorating condition of the small area of forest available to the birds and their resulting population decline saw the seven remaining birds transferred to a larger patch of bush on adjacent Mangere Island in 1976-77. After reaching a low of just 5 birds in 1980, intensive and innovative management combined with the extraordinary efforts of 'Old Blue', the only breeding female, saw the population increase to around 80 birds in 1989 with robins also having been established on Rangatira Island in 1983. At that time intensive management stopped, but intensive monitoring continued to monitor the growth of the population up until 1999, by which time the population had reached around 200 mature individuals. Seemingly secure on the pest-free island homes, monitoring was scaled back to allow work on other species.
Ngaio (Myoporum laetum) is an important rongoa and taonga for many iwi. As many a tramper will appreciate an infusion made from crushed leaves is an excellent way to soothe and treat grazes and infected wounds, while I can personally vouch that burning sprigs of fresh foliage does indeed, as old time Maori advised, repel even the most determined mosquitoes and sandflies! Also in Maori mythology it is a gnarled old ngaio tree that is said to have accompanied Rona on her involuntary trip to the moon. There can be little doubt that the humble ngaio has a special place in many peoples hearts, not only because of its medicinal properties and role in Maori myths but also because it is a hardy, fast growing, drought tolerant tree that provides excellent shelter in coastal areas from strong winds. Ngaio is also popular with gardeners because it produces a profusion of purple-spotted white flowers almost throughout the year, and these are followed by equally attractive quantities of purple or pink fruits. However, despite all these charms and uses it should be noted that all parts of the plant and especially the foliage are also extremely toxic (Connor 1977).
While our knowledge of New Zealand lichens is rapidly growing we are still unclear of what is present over large parts of the New Zealand Botanical Region. One key area of lichen ignorance is the Chatham Islands. The current lichen flora (Galloway 2007) records just 48 species for the islands. Yet despite that, the Chathams are the type locality for three species, and one of these, Caloplaca maculata, is endemic to the islands (see Galloway 2007; Johnson 2008; de Lange 2009).
In 1996 two of us, Peter de Lange & Gillian Crowcroft, visited the islands for their first time during which they collected a few lichens from the southern part of Rekohu (Chatham Island). Since then, but most especially in 2007 and 2008, Peter de Lange (mostly aided by Peter Heenan), has made a special effort to collect lichens to improve our knowledge of their diversity on the island. As a result of these gatherings, Peter de Lange and David Galloway (the author of the New Zealand Lichen flora series (Galloway 1985, 2007)) are working with the other key Chatham Islands lichen collectors Peter Johnson and Allison Knight, and lichenologist Dan Blanchon to prepare a checklist of the lichen flora for that island group (Galloway et al. in prep.). As part of that project they have been systematically working through all known collections from the island group held in New Zealand herbaria. In the process some rather interesting and at times unexpected finds are being made.
A common woodland lichen of eastern Australia that has been recorded only twice from New Zealand in 1934 and 1976, and then only from the far north of the North Island has turned up on the Chatham Islands. The lichen, Heterodea muelleri is a leafy species that in Australia grows in moderately open woodland habitats. In New Zealand, until it was recognised from the Chatham Islands it had only ever been recorded from dune slacks somewhere on the Ninety Mile Beach and from damp sandstone ridges in light scrub near Puheke, Karikari Peninsula.
The Chatham gatherings came from the north-western end of Ocean Bay, Chatham Island and from the top of Hakepa Hill (Walkemup), Pitt Island. At Ocean Bay the lichen grew on sandy peat and clay above schist on the margin of salt and wind blasted vegetation. In this habitat it was associated with the lichens Cladia aggregata and C. retipora, and sedge Lepidosperma australe. On Hakepa Hill specimens were gathered from amongst the dense drifts of Cladonia lichens that grow between the low, windswept fernland that covers most of that trachyte peaks summit.
The Chatham Islands Sow-thistle or Embergeria grandifoliais one of two endemic plant genera known only from the Chatham Islands. For most of the last fifty years the sow-thistle has been in decline throughout the Chatham Islands such that at one time it was ranked by the International Union for the Conservation of Nature (IUCN) as "Endangered" meaning that if the decline wasn't halted it would soon go extinct.
Since the late 1990s the Department of Conservation in cooperation with Chatham Islanders has been working to save this peculiar plant from extinction. While Chatham Island sow-thistle is probably not the most attractive looking of plants it is undoubtedly of world wide interest. Superficially resembling the introduced puwha/sow-thistles (Sonchus spp.), the Chatham Islands Sow-thistle is a much larger plant with flowering specimens sometimes reaching up to 1.8 m in height. The yellow-green leaves are very leathery and can be up to 1 m long, while the dense clusters of daisy-like flowers are produced in profusion and multi-coloured in shades of yellow, apricot and purple.
In 2005 whilst at the Allan Herbarium (CHR), Lincoln I happened to ask Dr David Glenny if anyone had examined the liverwort flora of the Chatham Islands? David told me that a few people had collected liverworts from there, including him in 1997, and so far found "nothing special". Intrigued, I then asked if David would like me to collect hornworts and liverworts while doing vascular plant work over there, and he agreed that this would be a good idea. David also kindly gave me a checklist of the hornworts and liverworts known to be on the island, and further, he agreed to identify what I got from there.
A major paper (Heenan et al. 2010) examining the origin of the Chatham Islands native flora has just been published in the June 2010 issue of the New Zealand Journal of Botany. The paper written jointly by staff of Landcare Research, Department of Conservation, and Universities of Auckland, Lincoln and Otago explores the origin and diversification of 31 endemic land plants (ferns and flowering plants) of the Chatham Islands archipelago using DNA sequences pooled from a variety of independent unpublished studies.
Hooker's spleenwort (Asplenium hookerianum) is not a particularly common fern on the Chatham Islands. By far the largest population the Department of Conservation knows about is one that was discovered in November 2008 along the banks of the Waipaua Stream, Pitt Island.
Hooker's spleenwort looks superficially like a smaller version of Hen & Chickens fern or pikopiko (Asplenium bulbiferum and the allied A. gracillimum), which is abundant on both Chatham and Pitt Islands. Aside from its size Hooker's spleenwort differs by the absence of "chickens" - small plantlets that develop on the frond, and which if dislodged are capable of growing, stalked pinnules - and depending on which form of Hooker's spleenwort you have, fronds with fewer, less-divided pinnules or fronds with more finely divided pinnules. Both forms have been called different species at one time - Aspleniumhookerianum for the less divided frond race and A. colensoi for the more finely divided type - but nowadays many botanists prefer to treat them as varieties or even as the one species A. hookerianum. As in New Zealand proper, on the Chathams both forms occur and usually grow side by side.
Until the close of the last century very little was known and next to nothing published about the mosses of the Chatham Islands. Although the first moss gatherings were made by Henry Travers in the 1860's it was not until 1997 that Landcare Research staff visited the islands to specifically study mosses and liverworts. Since then, partly to assist with the preparation of upcoming New Zealand Flora treatments on bryophytes, mosses and liverworts have also been gathered from Chatham Islands by scientists from of the National Institute of Atmospheric Research and Department of Conservation. From these aggregated collections we now have a reasonable idea of the Chatham Island moss flora.
Currently c.199 different mosses have been recorded from the Chatham Islands. Only one, Macromitrium ramsayae is endemic. A small number, perhaps six species, are naturalised and the remainder are indigenous to New Zealand, Australasia or the wider Pacific. Of these mosses the majority are widespread species found throughout the main islands of New Zealand.
However, a small number follow a pattern already evident with the islands flowering plants and ferns, which is that some mosses previously only known from northern and southern New Zealand, are now known to occur on the Chatham Islands.
Lichens are by definition any fungus and alga (or a cyanobacterium - oft known as blue green alga) living in symbiotic association. This overly simplistic description serves to explain away a vast amount of New Zealand's biodiversity. There is an estimated 2000 different kinds of lichen in New Zealand of which formal descriptions exist for no less than 1706! As a rule most people ignore lichens, often mistakenly confusing them with the very different mosses and liverworts "as just lichens". This is unfortunate, and increasingly we are beginning to appreciate that we do this at our peril. Lichens are proving to be the botanical equivalent of the canary in the cage, often providing the first warning signs of deteriorating air quality, pollution and temperature changes. Lichens too are proving useful in dating geological phenomena such as landslides and earthquakes, and lichens are major nitrogen fixers, contributing for example, 10 kg N per ha per year in the average New Zealand temperate rainforest ecosystem.
The south-west of Chatham Island encompasses dramatic coastal scenery, a fertile farming belt and forested catchments rising to a moorish tableland containing lakes and low peaks. The south-west supports the most extensive forest on Chatham Island, expanses of upland bamboo rush & Chatham aster and important populations of threatened plants and animals. It is the only breeding sites in the world for taiko and the Chatham Island mudfish. The largest protected area occurs here with the Tuku Nature Reserve and adjoining South Chatham covenant at about 2,500 hectares.
The tableland is highly distinctive. The flat to undulating topography belies the fact it is the highest region of Chatham Island at 250-280m altitude. The island's tallest peaks occur on the tableland's northern edge.