Extinction threat for giant land snail from Solid Energy’s Stockton mine

The first recorded extinction of one of New Zealand’s distinctive giant land snails could occur in the next 12 months if the State Owned Enterprise (SOE) Solid Energy continues to mine the only known habitat of the snail.

The claim is made in a report by the Department of Conservation which has been released to the Royal Forest and Bird Protection Society under the Official Information Act.

“Continued mining of the ridgeline north of Mt Augustus at Solid Energy’s Stockton mine in Buller risks the extinction of the recently discovered Powelliphanta “Augustus”. The snail’s only known population is on a small 5 ha site on the ridgeline,” Forest and Bird field officer Eugenie Sage said.

“The Government must stop Solid Energy from mining the remaining habitat of this new species and instead transfer the area to the Department of Conservation.

“Mining has already destroyed most of the Powelliphanta “Augustus” population. The few snails that remain are in an area of sub-alpine forest and shrublands which the SOE plans to mine in the next 12 months or so,” she said.

The report by DoC scientist and land snail expert, Kath Walker says mining the site “would cause the first recorded extinction of one of New Zealand’s distinctive giant land snails since European settlement”.

“The Government cannot allow its coal mining company to cause a species extinction,” Ms Sage said. “To do so would make a mockery of its New Zealand Biodiversity Strategy and international conservation commitments.”

“Solid Energy recorded a net surplus after tax of $17.5 million for the six months ended 31 December 2004. It can well afford to surrender a small part of its 2,310 ha mining licence area to the Department of Conservation to protect the snail.”

“Solid Energy’s track record of broken promises and serious environmental harm means Forest and Bird has little faith in any “promises” by the SOE not to mine the area in the short term.

“In February 2005 Solid Energy promised Buller community groups that it would not mine the dramatic ridgeline between Mt Augustus and Granity, which is visible from Westport and the seal colony at Cape Foulwind. Less than a month later, part of the ridgeline was mined in breach of the promise. Once again, CEO Don Elder greenwashed the problem by apologising for the company’s environmental mistakes, “ Ms Sage said.

The DoC report concludes that “not mining the site is the only option which ensures that Powelliphanta “Augustus” does not go extinct.”

Moving the snails to another site is not a viable option according to the DoC report. The snails have very specific habitat requirements. Powelliphanta “Augustus” only occurs in forested, high altitude coal measures with very high rainfall. Other similar sites on the Stockton Denniston coal plateau are either being mined, or are occupied by another snail species.

Taking the species into captivity is unlikely to work either. Trials in captivity with other giant land snail species have been unable to sustain viable populations in the long term.

NOTES

Please contact Forest and Bird for a copy of DoC report “The fate of Powelliphanta “Augustus” – a discussion document” obtained under the Official Information Act.

Powelliphanta “Augustus” was first found by members of the Nelson Botanical Society north-east of Mt Augustus in 1996. It was assumed to be another species, Powelliphanta “patrikensis”. In 2003 the shells were critically examined and found not to be “patrickensis” but a new species.

The area where Powelliphanta “augustus” were first found has now been mined, with the loss of all its snail inhabitants. Despite searches by Department of Conservation staff and Solid Energy contractors, only one remaining population of the snail has been located. This is confined to a small area of subalpine forest and scrub on the northern ridge of Mt Augustus.

The remaining Mt Augustus snail habitat lies close to the boundary between Solid Energy’s mining licence area and conservation land. The area was recommended for protection in the 1998 Ngakawau Protected Natural Area report, before the new snail species was identified.

The Significance of Giant Land Snails

(Information adapted from expert evidence by Kath Walker for Department of Conservation in recent Environment Court case on Solid Energy’s proposed Cypress coal mine).

The giant Powelliphanta land snails of North Westland and North-West Nelson are internationally significant. They are of very ancient lineage and originated in the late Paleozoic or early Mesozoic on Gondwanaland, along with the ancestors of native frog and tuatara (Stevens et al 1995).

Like the moa and weta, Powelliphanta land snails developed gigantism, and large flightless invertebrates took the ecological niche small mammals occupy elsewhere in the world.

Today there are about 24 species of Powelliphanta. Most are naturally confined to small areas, probably through a combination of a long and complicated biogeographical history, the snails’ restricted mobility, and habitat specific adaptation.

Powelliphanta snails vary greatly between species, most have very glossy shells, delicately marked with numerous bands, in many shades of red, brown, yellow and black. Some species are large, like the fist-sized, golden shelled Powelliphanta superba prouseorum, which weighs as much as a tui.

Like other pre-historic species such as kiwi and tuatara, Powelliphanta are slow-growing, long-lived (averaging about 12-15 years), and have low productivity. They do not reach breeding age until their 5th or 6th year, and lay only 4-10 hard limy eggs annually, with the survival of hatchlings likely to be low. They have few defences against predators. The alpine Powelliphanta have fared better than lowland species as most of the new snail predators are scarce above the bushline. Their small, patchy and localized distribution make Powelliphanta very vulnerable to habitat loss. Many Powelliphanta are now highly threatened species.

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