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Tuesday, 8 March 2016

Dunedin Climate Could Be Key To Survival Of Nelson's Endangered Coastal Peppercress

Dunedin’s notorious weather may hold the key to the survival of Nelson’s coastal peppercress (Lepidium banksii). Seedlings of this critically endangered species are being grown in a cooler climate at Dunedin Botanic Garden’s new propagation facility, in an innovative approach to safeguard the species from extinction.
Dunedin ecologist, Dr Mike Thorsen, organised the conservation programme on behalf of the recently launched Endangered Species Foundation of New Zealand (ESFNZ), and is also growing some of the plants. He believes the species should grow well in the absence of the pests and diseases that ravage its remaining natural populations.

A wild coastal peppercress plant on the Nelson coast (Photo: Department of Conservation).
“Coastal peppercress is a hardy plant adapted to the tough north-west Nelson coastal environment. But it has proved vulnerable to a large number of exotic pests and diseases: diamond back moth, pigs, several species of weeds, white rust, white cabbage butterfly, grey aphids, rabbits, hares, rats, mice, possums, snails, slugs, white fly and turnip mosaic virus”, said Dr Thorsen. “There was even an instance of a deer falling over a cliff onto a ledge inhabited by coastal peppercress and it ate everything it could reach”, he added.

Dr Thorsen said that the species would probably be extinct if not for the hard and persistent efforts of three Department of Conservation (DOC) workers.

Shannel Courtney of DOC, who has been protecting coastal peppercress for nearly twenty years, says the work is daunting, and for every sign of progress there would then come a set-back, “be it disease, a storm, or an unusually high tide dumping tonnes of driftwood on plants”. He and co-workers, Simon Walls and Roger Gaskell, together with other helpers over the years, attempted to establish populations at new sites as well as bolstering the last of the wild populations. “Unfortunately, our efforts have not been successful in increasing the number of coastal peppercress, and it is time to try fresh approaches”, said Mr Courtney.

Alice Lloyd-Fitt, Dunedin Botanic Garden’s Propagation Services Officer oversees apprentice Lucy Parsons sowing coastal peppercress seed in the new cultivation facility at the Dunedin Botanic Garden (Photo: Mike Thorsen)
It is thought that the cooler climate of Dunedin may mean that there are fewer pests and diseases present which would allow coastal peppercress plants to thrive. The Dunedin Botanic Garden Manager, Alan Matchett, says the role of the Botanic Garden is changing, and they are becoming more  involved in conservation programmes by providing their expertise in growing “difficult” plant species and using their state-of-the-art propagation facility which opened last year.

“We are intrigued by the challenges posed in growing coastal peppercress, and our involvement means that we not just answer the question ‘do we need to grow coastal peppercress in cooler environments?’, but we can also harvest seed from the plants grown here and these can be used to bolster the populations back in Nelson”, says Mr Matchett.

Seedlings of critically endangered coastal peppercress growing at Dunedin Botanic Garden (Photo: Liz Sherwood)
The coastal peppercress seeds were sown in December and germinated through January and February, with an approximate 60% rate of germination success. Dunedin Botanic Garden Propagation Services Officer Alice Lloyd-Fitt says they are now growing 89 healthy seedlings. 
The Endangered Species Foundation is pleased to be supporting this work. The Foundation was launched in October last year with the publication of its list of NZ’s ten most endangered species, of which coastal peppercress is number eight. Foundation chairperson, Kerry Prendergast, says “We want to help those who are working so hard to protect our rarest species. We also want to help facilitate innovative conservation efforts, such as this”.

The group has already raised over $1.5 million of its $30 million target.

Dr Thorsen said, “We’ve already lost two species of peppercress, and the remaining 18 endemic species are all close to becoming extinct for many of the same reasons as those threatening Nelson’s coastal peppercress. It would be a huge blow to lose plants that were once an important diet of Maori and were gathered by the ‘boatload’ by Captain Cook to ward off scurvy in his sailors. “What we learn with the coastal peppercress could be used to help these other species”, he said.

Volunteers are needed in Nelson to care for the remaining wild plants. Volunteers should contact DOC’s Takaka Office.

For more information on coastal peppercress please visit:
New Zealand Plant Conservation Network website search ‘Lepidium banksii’ (coastal peppercress)

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