I gave a talk on “Understanding and valuing our plants” at the recent open day of Otari-Wilton’s Bush in Wellington. I’m very interested in why New Zealand’s native species might be valued. I am hoping you can help me think about that – I welcome your input; look out for an upcoming blog post. But before that, some background on the numbers of plants in New Zealand.
The numbers of plants in New Zealand
Some 8500 different kinds of plants are indigenous to New Zealand. “Indigenous” indicates they are present in New Zealand without the intervention of humans. This total is made up of 2030 seed plants, 201 ferns and lycophytes, 480 mosses, 610 liverworts, 1800 lichens, and over 3000 (unicellular and multicellular) algae. These figures principally come from the recently published New Zealand Inventory of Biodiversity.
Many of these indigenous plants are endemic to New Zealand; that is, only found here. For example, c. 80% of the indigenous seed plants are endemic, and c. 45% of the ferns and liverworts.
Humans have greatly impacted New Zealand’s plants. The effects are best understood among the vascular plants (seed plants plus ferns and lycophytes).
According to the latest assessment, 42% of vascular plants are of some conservation concern. That seems alarmingly high, but it does include species with naturally small populations. 10% are formally Threatened. Comparing conservation rankings for vascular plants over time, it appears the trend is steady, if not worsening. Certainly, the collective conservation status of our vascular plants is not substantively improving; “clean green” New Zealand is not yet in full-blown remediation.
Uncertainty reins among other the plant groups; 54% of New Zealand’s lichens (975 ‘species’) are so poorly known that they cannot be assigned a conservation ranking. Many of New Zealand’s seaweeds have been recorded only a handful of times. Third rate understanding cannot enable first class environmental management.
Habitat loss and introduced browsers, pests, and competitors have all taken their toll on New Zealand’s indigenous plants.
Our indigenous plant species are now outnumbered by plants, mostly seed plants, introduced from elsewhere in the world. A few of the introductions are productive, some are pretty, but many would appear to have few redeeming features, at least in the New Zealand context. Among seed plants, there are now more weedy species than natives, and a very-roughly estimated 25 000 species of seed plants are cultivated in New Zealand.
New Zealand evidently has a lot of indigenous plants. Are they valuable to you? Why?
More information on the New Zealand Inventory of Biodiversity (Volume 3), which includes the plants.
Conservation status of New Zealand lichens, abstract.