Unsung Heroes Save Plant From Imminent Extinction
Coastal peppercress (Lepidium banksii Kirk: Brassicaceae) is perhaps the most threatened of New Zealand’s 11 indigenous species. Kirk described the species from material collected by French explorers during the Dumont d’Urville survey of the coastline of what is now the Abel Tasman National Park. He also recorded its presence in the Marlborough Sounds.Following Kirk’s publication the species remained known only from the original type gatherings until 1961 when it was collected by botanist Alan Esler near Totaranui. Evidently Esler did not know his specimens were L. banksii – he called them L. oleraceum - and their exact identity remained unchallenged until the indigenous and naturalised New Zealand lepidia were being revised by Phil Garnock-Jones for his treatment of the genus for Flora 4. A quick survey rediscovered plants along the coastline north of Totaranui, and at about the same time the species was found by Shannel Courtney during a survey of the vegetation and fauna of the Waimea Estuary near Nelson.
The conservation of the species has been particularly frustrating, for this plant perhaps more than any other of currently accepted 11 indigenous lepidia, seems to want to go extinct. Plants fall victim to a wide range of introduced plant pests and pathogens, are extremely difficult to maintain in cultivation (best treated as an annual) and have proved well nigh impossible to plant out successfully in the wild.
The plight of the species was so bad that by 1990 only 26 plants were known from the wild. In 1994 Simon Walls was delighted to find a large natural population (450 plants) growing on sand dunes at remote Mutton Cove. Sadly so were – of all things – the local wild pigs, and within months of the find none were left at this site. The battle to save the plant continued, various low lying islets, rock stacks and islands were commandeered across Tasman Bay, with plants optimistically planted out each year. All died, some within weeks, all within a year.
By 2000 it was agreed that the strategy of growing plants up and planting these out was doing little for the species. A new tactic was trialled, Simon Walls armed with a grubber, a bag of seed and lots of optimism, sallied forth along the Abel Tasman coastline looking for sites where seals, shags, penguins, terns or gulls congregated. Often forced to construct mini walls from the hard granite rock on otherwise improbably steep cliff faces, he grubbed out weeds, scratched the ground to gather enough of the coarse soil, and scattered handfuls of seed. Within weeks his efforts produced seedlings and miraculously at most sites these grew. By 2005 there were 183 plants in the wild. Oddly Walls found that during drought years the species did the best, wet summers appear to favour rank weed growth and disease. Walls is modest of his work “Its only gardening but in what a landscape!”. What is clear is that gardening or not, without this dedication the species would now be extinct. There are no naturally occurring wild plants left, all that are known are the product of Walls, Courtney’s and other Motueka based Department of Conservation staff efforts.
The funny thing about this story is that almost no one in New Zealand knows anything about it. Yet the coastal peppercress, despite its non-assuming character is every bit as important to global diversity as many other high profile animals whose conservation is backed to the hilt by sponsors and conservation resources. Funny how two men, a grubber, and lots of dedication has so far prevented yet another unsung plant’s extinction.
Posted: 12/07/2006