NZ native plants face threat of extinction

Brightly coloured kaka beak is dwindling in the wild - putting it at risk of becoming more common in British gardens than it is in its natural home.

It is one of 180 native plants on an endangered list compiled by the Department of Conservation, which found that urban expansion, farm conversion to dairy and a growing number of vineyards were pushing increasing numbers of native plants towards extinction.

The number of threatened plant species has risen from 122 five years ago to 180 - about 7.6 per cent of New Zealand's native plants.

Only one wild specimen was found of Clianthus puniceus, the smaller of two kaka beak shrub species, in New Zealand.

The plant is named for its scarlet flowers shaped like the beak of New Zealand's native parrot.

The other, Clianthus maximus, has dwindled from 2000 known wild plants in 1990 to just over 150, as goats and hares munched the plants faster than people could grow them.

DoC botanist Peter de Lange said the larger kaka beaks, which were found in the wild mostly on the East Cape, had suffered after a boom in rounding up wild goats for farming in 1980s ended and many goats escaped into the wild.

DoC surveillance cameras also caught a hare devouring a 1m kaka beak in about five minutes - "sucking it up like spaghetti", said Mr de Lange.

Kaka beaks do have some human helpers. Mr de Lange said the efforts of East Cape school children had been the single biggest factor saving kaka beak from extinction.

Children from schools between Tolaga Bay and Hicks Bay, led by DoC ranger Graeme Atkins, "more than anything else" had saved wild kaka beak by planting the bright red blooms along SH35.

But most wild kaka beaks were on private land and so it were out of DoC's control, he said.

The DoC survey placed many plants on the endangered list. New Zealand broom (Carmichaelia carmichaeliae) is in the critical category in Marlborough, and Bartletts rata (Metrosideros bartlettii) is in danger in Northland.

Although kaka beak is popular in gardens, genetic diversity would be lost without plants.

The smaller kaka beak species has fallen out of favour with New Zealand gardeners, and it is now mostly the larger species that is grown.

Mr de Lange said the smaller kaka beak was more often grown by gardeners in Britain than in New Zealand.

Part of the increase in the number of endangered plants could be attributed to the discovery of new species of plants with naturally small populations, he said, but most threatened plants had declined after changes in their environment.

Scientists had discovered a new species of tree or shrub every year since 2000 - sometimes too late to save the species from extinction.

One new shrub was down to seven plants when it was discovered, and all the surviving plants were female.

"That's it - it's gone," said Mr de Lange.

Some newly discovered plants - such as a new species of pepper tree or horopito found in a Northland backyard - contained rare compounds that can be used by medical researchers.

Mr de Lange said there was no one reason plants were struggling. It was a symptom of a wider problem - that changing land use was not being managed in a way that preserved the natural environment.