A highlight of my recent South Island fieldwork was helping to survey the last remaining New Zealand population of the liverwort Petalophyllum preissii. It’s a distinctive looking plant, a bit like a little lettuce, and about the size of a fingernail.
Seeing it was special because I likely won’t have the opportunity again. You’ll probably never have the chance to see it alive in New Zealand either, unless there is a radical change in its fortunes.
Led by Landcare Research’s liverwort expert, David Glenny, we found only 36 plants, at a site near Kaikoura. That’s the entire New Zealand population. Numbers have nearly halved since it was last surveyed several years ago.
Populations of Petalophyllum preisii elsewhere in New Zealand have completely disappeared. The reasons for their decline are unclear. At Kaikoura, David Glenny thinks it is being shaded out by introduced grasses, particularly Festuca rubra.
Other than the cutting of some surrounding scrub, Petalophyllum preissii does not seem to be receiving any assistance. It does occur in Australia and, although uncommon there too, perhaps that’s the reason New Zealand’s plants are being allowed to drift to extinction.
Is this case unusual?
While the continued existence of Petalophyllum preissii in New Zealand is especially precarious, lots of other native plants are faring poorly too. 235 different kinds of our native vascular plants (seed plants, ferns, & lycophytes) are formally Threatened; that’s 10%. A further 683 are At Risk (28%). These native plants species (or subspecies or varieties) have declined since humans arrived in New Zealand or are naturally rare. Either way, there is now real concern that we and our introduced menagerie might eliminate them, without care and intervention.
Is it getting better? The latest assessment for vascular plants (link below) referenced just 2 species that “experienced an actual improvement in their status through management”. The 235 kinds of vascular plants regarded as Threatened was up from 180 in the assessment four years previous.
It is arguable whether ‘clean and green’ New Zealand is living up to its reputation when it comes to looking after its indigenous vascular plants.
If this is the treatment of our ‘big’ plants, what attention might we afford our ‘little’ plants like Petalophyllum preissii and its liverwort brethren? Being small, they are easily overlooked as part of our natural heritage.
Who cares and who is responsible? Maybe the philanthropic Endangered Species Foundation will ride to the rescue.
Website of the Endangered Species Foundation.
What do you think? Should New Zealand try to save its population of Petalophyllum preissii?
Do we need New Zealand’s indigenous species? Te Papa blog post.
How many plants are in New Zealand? Te Papa blog post.
Plant collecting in south Canterbury and Marlborough. Te Papa blog post summarising the other aspects of our trip where we saw Petalophyllum priessii. For the record, we didn’t collect a specimen of it; it’s too rare for that.
Conservation status of New Zealand hornworts and liverworts, 2014. Department of Conservation report (pdf).
Conservation status of New Zealand indigenous vascular plants, 2012. Department of Conservation report (pdf).
Environment Aotearoa 2015, report by Ministry for the Environment (pdf). See figure 41 on page 109 which indicates the number of species assessed as Threatened is increasing.