As progress toward the preparation of the first flora of the Chatham Islands since 1864 Department of Conservation and Landcare Research scientists have published a new checklist of the plants of the Chatham Islands group (de Lange et al. 2011). The checklist not only provides the first full vouchered listing of the endemic, indigenous and naturalised flora of the islands to ever be published but also a brief history of the discovery of the Chatham Islands flora by European and later New Zealand scientists covering the period between 1840 and 2011. The checklist also describes the origins of the Chatham Island flora, and provides the first detailed discussion and assessment of the indigenous and naturalised plants to be published since the early 1900s.
The checklist accepts 875 formally described vascular plants for the island. Vascular plants are a ‘catch-all’ covering a diverse grouping of plants that includes clubmosses, ferns, conifers and flowering plants. The publication also notes that a further 27 plants found on the islands are new and still require formal taxonomic description. At this stage 41 formally described plants are considered endemic to the islands, a figure which includes two endemic genera, the spectacular, world famous Chatham Islands forget-me-not (Myosotidium) and Chatham Islands sow-thistle (Embergeria). There are also 400 indigenous plants and 434 that are regarded as naturalised to the islands. Of the 27 as undescribed plants, 13 are believed endemic to the islands, the remaining 11 are known also from New Zealand. A peculiar pattern that warrants further study is that many indigenous plants are known from five or less sites on the islands, and there is some evidence to suggest that the islands are still being naturally colonised by plants from New Zealand.
It is also abundantly clear that for its size the Chatham Islands has a very remarkable flora with the highest levels of endemism yet known from any of the outer islands of the New Zealand archipelago (and this includes Stewart Island!).
However, the authors caution that the flora is at risk, especially from a steadily increasing influx of weeds. They note that while many past weeds have arrived in machinery and as accidental contaminants in grass seed and other agricultural supplies, a significant number of recent establishments are derived from garden material bought from New Zealand. These weeds include such environmentally damaged pests as Chilean rhubarb (Gunnera tinctoria) and lady fern (Dryopteris affinis). In the checklist a table outlining which weed families have yet to establish on the islands is given, the listing noting that this table includes 28 families whose members, if they become established on the islands, will prove a major headache not only for conservation workers but also farmers, fisherman, hunters and indeed landowners as a whole. It is especially concerning that some of these major weed families are already present in private gardens, e.g., oxygen weed (Egeriadensa and Elodea canadensis). It is only to be hoped that through this publication islanders will be better informed about what plants they don’t want establishing on their island, or the current nightmares of ragwort (Jacobaea vulgaris), gorse (Ulex europaeus) cranberry (Ugni molinae) and blackberry (Rubus fruiticosus) they face will pale into insignificance as waterways and favoured eeling grounds become choked with pests like oxygen weed and royal fern.
The next phase of preparing the Chatham Island flora is now underway, at this stage a three volume hard back series is envisaged, the first volume of which will document the clubmosses, ferns and conifers of the islands.
The new checklist is available free as a download from the New Zealand Department of Conservation website www.doc.govt.nz
- de Lange, P.J.; Heenan, P.B.; Rolfe, J.R. 2011: Checklist of vascular plants recorded from the Chatham Island Islands. Department of Conservation, Wellington. 57pp.