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.
New Zealand has about 10% of the worlds lichen flora, 23% of which are treated as endemic (i.e., found nowhere else but New Zealand). For our size this is an impressive figure, Australia which is many times larger has for example an estimated 35% of its lichen flora endemic. While our knowledge of New Zealand lichens is rapidly growing we are still unclear of what is present over large parts of the subcontinent. 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, one of which, Caloplaca maculata is endemic to the islands.1
Despite some initial gatherings of lichens made from the islands by Henry Travers in 1864, followed over the last 100 or so years by a few other botanists, much of our present knowledge of the Chatham Islands lichens has come from the pioneering work of former Conservation Board Chair Dr Peter Johnson. Peter has made a concerted effort to collect lichens from the islands, most especially the outer islands and also from lichen groups others tend to ignore. Indeed it was Peter's efforts that resulted in the discovery of Caloplaca maculata. However, despite his hard work it is clear that our knowledge of the Chatham Island lichen flora is still very rudimentary and that more collection effort is needed to obtain a better idea of what is out on the islands.
To that end, and despite their reputation for being difficult to identify Department of Conservation staff have been working closely with Landcare Research to try and better sample the islands ecosystems to see what lichens are present on the island. This has meant the painstaking sampling of a range of ecosystems and habitats, and the careful curation of the gatherings back in New Zealand. One particular lichen, Sticta fuliginosa even had the authorities back in New Zealand very excited. This species reeks of fish as it dries, so the innocuous little plant caused some consternation for botanists at both Christchurch and Auckland airports when its presence attracted the attention of a paua dog last May! Its smell lead to some involved explanations as to why a series of boxes labelled "Lichens" smelt like paua, and that "No we were not paua smugglers".
Results based on the September 2007 and May 2008 major lichen collecting efforts are still coming in. Indeed some gatherings have had to be sent to the United States and Europe to be identified, while others will probably remain in their collection bags awaiting the day when some future researcher will take an interest in a particular genus or group of lichens.
Nevertheless, and despite these inevitable delays in identification, we now have better collections spanning the main islands of the Chathams group, and the key ecosystems on offer. Currently, 239 types of lichen are known from the islands, that's a 398% increase on what we knew in 2007!
Again, as has been demonstrated by other studies of Chatham Island liverworts and mosses, the Chatham Lichen flora shows the same intriguing mix of tropical and northern New Zealand species with southern New Zealand and subantarctic species. Indeed some associations you are very unlikely to see anywhere else in the New Zealand subcontinent, for example on Pitt Island one can see the tropical lichen Ramalina luciae growing with the subantarctic R. inflata, both reaching their respective world southern and northern limits on the island. While a drive to the Awatotara will reveal masses of the normally alpine Usnea acromelana festooning the roadside banks at a mere 100 m above sea level. On Pitt parts of the summit crest of Hakepa (Walkemup) are covered in the worm-like Thamnolia vermicularis - a species that is more commonly seen high up in the Southern Alps of the South Island! While coastal and swamp forest trees on both Chatham and Pitt are often festooned in Usnea angulata and Pseudocyphellaria aurata, two lichens more commonly seen on mangroves in northern New Zealand. Also there are some genera that have an unusually high representation on the islands. For example 13 of the New Zealand's 28 species of old man's beard (Usnea), and 35 of New Zealand's 38 species of Pseudocyphellaria are known from the islands. The island also supports thriving populations of species that are becoming scarce in New Zealand or even globally. For example, the brilliant orange air pollution sensitive Teloschistes flavicans and the peat bog dwelling Icmadophila splachnirima are locally common on the Chatham Islands.
As with liverworts and mosses the dearth of endemics on the islands flies in the face of the flowering plant and fern flora which contributes an estimated 50 to the Chatham flora. There are still no endemic liverworts known from the islands and only one moss, the doubtfully distinct Macromitirum ramsayae is considered endemic. The sole Chatham endemic lichen, Caloplaca maculata also remains on the uncertain list. Although it is a distinctive species until better collecting of this genus is undertaken elsewhere in the New Zealand subcontinent we just can't be sure if it is truly endemic. Irrespective of that, it possibly also qualifies as one of the Chatham Islands most threatened lichens. Currently it is known from just one coastal rock platform, where it grows on a hard exposure of basaltic tuff just above the spray zone. The little plants cover an area of c.2 × 3 m, and while several hundred individuals exist at this site, that population's eventual loss from coastal erosion is inevitable.
1. Caloplaca maculata is no longer recognised as endemic - see: http://www.chathams.co.nz/index.php/naturalheritage/138-lichen-no-longer-endemic