Mining area native life treasure chest

Denniston Plateau is a unique landscape and is home to rare life-forms such as <i>Powelliphanta...
Denniston Plateau is a unique landscape and is home to rare life-forms such as <i>Powelliphanta patrickensis</i>. Photo by Craig Potton.
<i>Powelliphanta patrickensis</i>. Photo by Forest and Bird.
<i>Powelliphanta patrickensis</i>. Photo by Forest and Bird.

Sir Alan Mark and Rod Morris say opencast mining on the Denniston Plateau would devastate an extensive area of unique conservation land.

We have been dismayed that, just two days after the general election, Minister of Conservation Kate Wilkinson, and then acting Energy Resources Minister Hekia Parata, jointly approved the proposal of the Australian mining company, Bathurst Resources, to establish a major opencast coal mine on public conservation land on North Westland's Denniston Plateau. Not only did this approval constitute a broken promise (it was contrary to a pre-election promise by both ministers last July that "significant applications to mine on public conservation land should be publicly notified") but it also clearly flies in the face of worldwide concern for continued global warming associated with the burning of a wide range of carbon compounds.

New Zealand should be seriously addressing its global responsibilities in curbing greenhouse-gas production rather than apparently ignoring this, apart from its promotion of aforestation. These are critical times for addressing global warming, recent international conferences in Copenhagen and Cancun having been unable to reach agreement on a successor to the Kyoto Protocol which expires in a year's time, and now Durban which seems to have made some progress.

The public must demand a say on this proposal since it will devastate an extensive area of unique conservation land, unlike anything else in New Zealand apart from the nearby Stockton Plateau to the north, where Solid Energy operates a similar massive opencast mine, which is now off-limits to the public but highly visible from the air or on Google Earth. The Denniston proposal clearly constitutes a "significant mining application" and justifies full public consultation.

The planned more than 160ha opencast mine and associated works, including a large coal-processing plant, pipelines and power lines, would destroy most of the unique heritage landscape and biological features of the Denniston Plateau. Although the plateau has had several small underground mines in the past, it has so far been spared the massive destruction of opencast mining.

However, this would change dramatically if Bathurst Resources were allowed to proceed with its proposal to mine up to 80 million tonnes of coal from the relatively pristine Denniston Plateau. This area has already been recognised by a Forest Service scientific committee in the 1980s (of which Prof Mark was a member), as well as a Government Protected Natural Areas Survey in the late 1990s, as unique and so important as to justify formal protection.

The boulder fields of acidic rock are known from only two locations, within the Denniston's Deep Stream catchment and on the upper slopes of nearby Mt Rochfort, while the more extensive sandstone pavements likewise occur at only one other location in New Zealand. The 1200ha Mt Rochfort Conservation Area was one of the protected areas resulting from these assessments. Formed 40 million years ago, this area is a treasure trove of 18 mostly dwarfed plant communities, bonsai gardens with an abundance of the world's smallest conifer, the pygmy pine, dwarfed southern rata and manuka, plus a wide range of cushion plants and stunted grasses occupying the dissected and patterned sandstone pavements.

These grade down into gullies filled with taller forests of mountain beech, pink pine, rata and mountain cedar. Several rare and threatened plants are present including the threatened local snow tussock Chionochloa juncea and red mistletoe.

Although the Denniston was identified as a place of outstanding ecological interest as far back as the early 1980s, much of the richness recognised was botanical. In the intervening years, we've begun to gain a sense of a truly fascinating invertebrate fauna endemic to the plateau as well.

Among these so-called "smaller animals" are several cryptic, and poorly known "giant" invertebrates such as the endemic land snail Powelliphanta patrickensis, several species of giant leaf-veined slugs, a mysterious giant "cream" ground weta (described by one observer as "looking like an ordinary weta on steroids").

There is also an egg-laying peripatus and a large, brightly coloured giant flatworm - so rare it has only ever been sighted once. Many of these animals are new and undescribed, several are among the largest known of their kind, and a remarkable number are earthworm predators. The abundance of earthworm predators may in turn reflect the hidden "biological wealth", at present poorly understood, but now being revealed as living in these so-called "poor" coal measure soils.

We are discovering there may be a great variety of native earthworm species living there. An earthworm scientist employed by Solid Energy identified more than 20 native earthworm species to date, in the topsoil and surface litter on the Stockton/Denniston Plateau - more than previously known for the entire West Coast. No doubt further new earthworm species will come to light once subsoil species are also sampled.

There is evidence of further unidentified earthworm species' being found in genetic material taken from the gut of the land snails; perhaps revealing the snails themselves know more about the plateau's earthworms (and their whereabouts) than the scientists! The plateau is both a fascination and a frustration to biologists. Even seemingly obvious species are tucked away out of sight. Native birds such as the South Island fernbird, South Island robin, Western weka and South Island kaka all live on the plateau, but not out in the tussock and heath areas. Instead they live tucked away in the many small forested stream gullies and river gorges which form unexpected oases and barriers, in hidden corners and unexpected features right across the plateau.

While these forest birds are regarded as vulnerable to introduced mammalian predators at other South Island lowland sites, strangely this does not seem the case on the Denniston. It's possible the extreme environment of the plateau deters many introduced mammalian predators. Features of this unique environment that seem on the one hand to protect the hidden endemics, yet prove unattractive to recently introduced animals such as rats, possums and mustelids, may include saturated acidic soils (the plateau functions rather like a wetland), cold desiccating winds year round, coupled with long-lying blankets of snow in winter and hot baking sun in summer. In effect, the plateau may be functioning as a large mainland island, protecting its native inhabitants from many of the changes that have swept through other lowland sites since humans arrived.

Two other native species stand out as significant on the plateau. The West Coast green gecko is the most divergent of the green geckos found in the northern South Island. It is poorly known throughout much of its range, because it is difficult to detect. Sporting the sort of camouflage a soldier would be proud of, the complex and intricate patterns of this "mossy" gecko are highly effective among the fern, moss and lichen-strewn rocks of its range throughout northern Westland. On windy days on the Denniston Plateau the species basks virtually undetected on stunted manuka or in sheltered hollows on the mossy ground, invisible to all, just so long as it doesn't move.

The other native to stand out up here is a kiwi. A dark, West Coast form of the great spotted kiwi lives in the wet forest on the western side of the main divide.

Found through Northwest Nelson, the Paparoa Range and near Arthur's Pass, the Denniston Plateau birds are distinctive. Because of introduced predator numbers in other lowland areas, great spotted kiwi today are mostly found at higher altitudes. Their favourite habitats are tussock grassland, scrub and forest, all of which occur on the Denniston Plateau. With introduced predator numbers low on the Denniston, great spotted kiwi appear remarkably to be holding their own - and at a lowland site! Mining would undoubtedly change all that.

Disturbance of soils and vegetation would encourage the spread of weedy species, and the inevitable invasion of predators.

Despite changes to mining legislation back in the 1990s, mining activity still enjoys privileged status over other land uses in this country. Mineral access agreements on public land (including conservation land) are, it seems, still to be negotiated in secret without public process, and without open assessment of the environmental effects. Or to put it more simply, an Australian mining company (or any other for that matter) apparently has more rights and privileges than our own endangered great spotted kiwi, even in areas already formally recognised for their special heritage values. Should we accept that?

Is that really what we want? What would future generations think of us, permitting this in the 21st century?

 - Alan Mark FRSNZ, KNZM, is an emeritus professor in the botany department, University of Otago, while Rod Morris is a local conservationist and natural history photographer.


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