Chatham Island linen flax

New Plant Threat Listing Includes Chatham’s Species

The May 2012 threat assessment of the New Zealand Indigenous Vascular Plant flora is now published (see de Lange et al. 2013). The list which covers the entire indigenous vascular plant flora, including that of the Chatham Islands and 166 informally recognised, ‘tag name’ entities is now available at http://www.doc.govt.nz/upload/documents/science-and-technical/nztcs3entire.pdf  as a free downloadable PDF.

Hebe barkeri
Hebe barkeri – the world’s tallest species of Hebe remains seriously threatened. Initially this Chatham Islands endemic appeared to be recovering in those parts of the islands where possums were being controlled. However recent field surveys indicate that it remains a very uncommon plant, and in many places, particularly on Pitt Island it is actively declining. This image of a Chatham Island plant held in cultivation at Te One. Image: Peter de Lange

The listing was undertaken by a panel of experts appointed by the New Zealand Department of Conservation and New Zealand Botanical Society. The panel has a wide representation of experts from Crown Research Institutes (NIWA, Landcare Research), museums, universities and the Department of Conservation.

In a departure from previous threat assessments, which have been published through the peer-reviewed scientific periodical ‘the New Zealand Journal of Botany’, the 2012 listing has been published in a new series set up by the Department of Conservation, the ‘New Zealand Threat Classification Series’. These publications are also peer-reviewed. The series was set up as a deliberate measure to ensure that any person, anywhere in New Zealand or the world was able to obtain free of charge the threat listings for all of New Zealand’s biota.

The current plant listing, which is the 10th to be published for the New Zealand flora continues a process pioneered by the late David Given in 1976. Given was arguably the first New Zealander to draw to world attention the plight of our native flora.

Since Given’s first listing eight native plants have now been listed as extinct, a figure which includes plants like Logania depressa that was seemingly simultaneously discovered, and wiped out by missionary botanist William Colenso in the early 1840s. The most recent addition to that list is the newly described scurvy grass (Lepidium amissum) which actually went extinct in 1917 but was only recognised as a distinct species in 2013.

Hebe barkeri on Pitt Island
Flower colour in Hebe barkeri varies from island to island, and this suggests that there may be significant genetic variation. Here is a highly coloured form of Hebe barkeri – this flower colour is typical of Pitt Island, where pink-flowered races are also known, whereas those on Chatham Island are fairly uniform in their colour. Image: Peter de Lange

While the current list of extinct flowering plants involve taxa whose loss happened prior to, or around 1954, it’s clear that we are potentially facing a new wave of plant extinctions. These will be extinctions that can no longer be swept away using the excuse of historical ignorance as our justification. Indeed it may surprise New Zealander’s to learn that even such iconic taonga as the red-flowered kakabeak are still facing imminent extinction. Of the two species, one, the eastern North Island C. maximus now exists with a national population of c. 120 individuals, whilst the other, the Northland endemic C. puniceus is still only known from just the one wild plant.

Indeed since the last listing was prepared in 2008 there has been an increase of 46 plants in the category ‘Threatened’, bringing the total number of plants facing a high risk of extinction to 289 (12% of our known flora). This is an alarming trend which reflects a wide range of threats to our native plants which include not only the familiar ‘loss of habitat’, ‘predation from introduced animals’, ‘competition from weeds’, and ‘changing land use practises’, but also the spread of plant diseases, including exotic viruses, which are increasingly being found in our indigenous flora. In the case of viruses it’s not yet clear whether this is a new trend, or simply that we are seeing part of a process that has been going on for a long time, but which we are only now just beginning to research, and so detect.

Spider orchid
Corybas aff. sulcatum – this unnamed spider orchid was once thought to be endemic to the Chatham Islands, though it was believed to be closely allied to a species endemic to Macquarie Island. However, an on-going investigation by Te Papa Museum of New Zealand Orchidologist Dr Carlos Lehnebach has confirmed that the Chatham’s plant is actually the same as an unnamed species found in the South Island. Situations such as these are becoming more common as more detailed biosystematic work is undertaken on the New Zealand flora, and in this case a lessened threat status now applies for what had been regarded as a Chatham Island endemic. Image: Peter de Lange

However, a big factor in the increase of threatened plants has also been, ironically, better science. It is estimated that 20% of our vascular flora still requires formal description. As those scientists concerned with the naming of our native plants and animals review our biota, many new species are being discovered, or often as not ‘rediscovered’, and not surprisingly many of these are threatened, or if not extremely uncommon. For plants a prime example is the June 2013 publication in the international journal PhytoKeys of a revision of Cook’s scurvy grass (Lepidium oleraceum), where 10 new species were segregated from Cook’s scurvy grass. All of these species are seriously threatened. For New Zealand, this situation is not that unusual, and indeed more threat listings (and possibly a few extinctions) are anticipated when on-going revisions on Craspedia, Cardamine and Euphrasia, two of which are due for completion in 2014 are published. Nevertheless while it increases the proportion of threatened plants in our flora, the process is encouraging in that it shows that the full extent of our indigenous biodiversity is finally beginning to be recognised. This is critical if we, as a nation are to make sensible decisions about managing our flora and fauna.

Threat listing is a critical pathway toward ensuring we have a better understanding of our countries conservation issues. The routine listings are used by many different walks of life, such as researchers, students and organisations to help determine conservation priorities and to establish more effective networks toward preventing further erosion of New Zealand’s biodiversity. It is salutary lesson that with the publication of each plant threat listing there has been corresponding increases in the numbers of people empowered by that process, and who want to help, and who go out there and look. This is to be applauded, particularly as threat listing is only as good as the data that flows in to support it.

Spider orchid flower
The flower of Corybas aff. sulcatum – an unnamed spider orchid. Image: Peter Heenan

Reference

de Lange, P.J.; Rolfe, J.R.; Champion, P.D.; Courtney, S.P.; Heenan, P.B..; Barkla, J.W.; Cameron, E.K.; Norton, D.A.; Hitchmough, R.A. 2013c: Conservation status of New Zealand indigenous vascular plants, 2012. New Zealand Threat Classification Series 3. New Zealand Department of Conservation, Wellington, New Zealand. http://www.doc.govt.nz/publications/science-and-technical/products/series/new-zealand-threat-classification-series/