Case study: Saving one extremely rare native plant illustrates the work ahead
Efforts to save one critically endangered plant illustrate how much needs to be done if a draft threatened species strategy released last week will succeed. Will Harvie reports.
The patchwork effort to preserve New Zealand's most threatened plants is illustrated by an extremely rare daisy that grows naturally only in Canterbury and has been raised and studied in Wellington.
The critically endangered "dry plains shrub daisy" (Olearia adenocarpa) is failing to regenerate in the wild, says primary researcher Dr Debra Wotton. There are fewer than 700 adult plants left and it is ranked among the 50 most threatened New Zealand plants.
The daisy is one of 150 animals and plants that will get "enhanced" protection under the Draft Threatened Species Strategy that Minister of Conservation Maggie Barry released last week.
Working from Wellington's Otari Native Botanic Garden and Wilton's Bush Reserve – the only public botanic garden dedicated solely to native plants – Wotton germinated the daisy and Otari staff raised the plants over the last 18 months.
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Simultaneously, Wotton was conducting field trials to determine how best to return the plant to the wild in Canterbury.
The daisy only occurs naturally in the Waimakariri and Rakaia river flood plains in Canterbury, where it occupies stony, sandy areas in former river channels, Wotton says. It likely colonised these sites after floods deposited fresh sediments.
But flood protection works have reduced flooding and stopped creation of the daisy's preferred habitat.
Meanwhile, historical burning and grazing by stock have replaced native shrub lands with non-native grasslands. The daisy cannot compete with non-native grasses.
In short, almost all of the ecosystem needed by the daisy is missing.
Efforts to preserve the daisy in the wild have included fencing – especially to stop browsing by hares and rabbits – and spraying herbicide on non-native grasses. But these programmes are expensive, intensive and cover relatively small areas.
Wotton's work has two aspects. First, she has germinated the dry plains shrub daisy at Otari, a successful effort that will see 70 sub-adult individuals sent to Christchurch City Council. The plan is for Department of Corrections crews to plant them out later this year. (Otari will keep about a half dozen daisies for its own collection and as insurance in case the species fails in Canterbury.)
Incidentally, germinating natives is not necessarily straightforward. Efforts at Otari to raise other rare natives have sometimes failed, says Rewi Elliot, acting manager of Wellington Gardens. In one case, the plants were dead within weeks of planting in the ground.
A second aspect of Wotton's research is getting the daisy to thrive in wild conditions in Canterbury. Simply plonking the plants into suitable ground isn't worthwhile because they can't compete. An answer is habitat restoration, a much more ambitious project.
Working with Environment Canterbury and the University of Canterbury, Wotton is conducting field trials testing whether shade and shelter, including from other native shrubs but also constructed wooden shelters with shade cloth, can help the daisy survive in the wild.
Wotton and colleagues are also testing "natural disturbance regimes" by adding gravels to growing sites. These replicate in some measure the daisy's preferred habitat.
Wotton said germinating the daisy and the habitat research were initially separate projects. But having raised the plants, it would have been a waste to not send them to Canterbury.
Otari was keen and she worked her connections in the southern city to bring the various agencies, and the Department of Corrections, together.
"For a lot of species, we don't know why they are declining or how to reverse that decline," says Wotton. "My research help us a get a handle on that and helps us reverse the decline."
Wotton got her PhD in Ecology from University of Canterbury, worked as a scientist at Department of Conservation and Landcare Research. In 2013, she founded Moa's Ark Research, a consultancy firm providing ecological services on native biodiversity. She also a research associate at the University of Canterbury and works from Otari.
Her daisy research is funded by science grants, plus assistance from Otari, ECan, city council, Canterbury University and doses of her volunteer time.
The draft Threatened Species Strategy released last week will – if it survives public consultation intact – "manage 500 [NZ] species for protection by 2025 ... and 600 species for protection by 2030".
In addition, it identifies 150 species for enhanced protection, "ensuring that the long-term health of 150 threatened and at-risk species will be improved". The top 50 of these are "notable to New Zealanders and currently receiving management".
Think kiwi, kakapo, maui dolphins, tuatara and the like. Just five plants make the top 50, including Bartlett's rata.
The next 100 contains 34 plants, including the dry plains shrub daisy.
It's not clear from the draft document what "enhanced protection" means for the daisy or Wotton's research.
The daisy research programme illustrates – depending on point of view – how many organisations and individuals are already working together to preserve rare plants and shows exactly where the draft strategy can help.
Alternatively, it shows how patchwork current efforts are. Otari, for example, is funded entirely by Wellington City Council but assists with rare plants and trees from around the country, including Northland, Whanganui, Otago and Canterbury.
The daisy research is driven by a private consultant volunteering some of her time and working connections with, among others, the Department of Corrections. They could use some help.