Whirinaki dispute flares up again; what happened in 120 AD?

Press, 20 September 1980, Page 15

Whirinaki dispute flares up again; what happened in 120 AD?

OLIVER RIDDELL

After 12 relatively quiet months, the battle between the Forest Service and villagers of Minganui, on the one hand, and conservationists on the other, over the selective logging of Whirinaki forest, southeast of Rotorua, is about to erupt again. This time the argument may be even more bitter because of a growing be--1 i e f among conservationists that the Forest Service has deliberately misled them.

That charge may prove impossible to justify. What is now becoming clear, however, is that the Forest Service has acted more quickly than it indicated it might, and that the premise under ■ which it justified logging in Whinnaki cannot be sustained scientifically.

The dispute was calmed 12 months ago when the Forest Service indicated it was conducting scientific trials on regeneration of lowland native softwoods in Whirinaki. If these proved successful, then it would go ahead with its milling programme. The Forest Service is now 7 pressing ahead, but a growing body of opinion within the public service and among the general

public is beginning to question whether 12 months of study constitutes a scientific trial. These critics now believe that the Forest Service never intended to conduct a proper scientific trial, and simply used the trial as an excuse to diffuse opposition while it carried on logging. Damaging to the Forest Service proposals to manage and selectively log in Whirinaki is a paper by Mr Kevin Hackwell, of the D.S.I.R. Ecology Division, which challenges the _ historic concept of Whirinaki on which the Forest Service has based its policy. And the matter, incredibly, goes back in history for 1860 years — in fact to 120 A.D. In a nutshell, the Forest Service believes that the dense lowland native softwood forests at Whirinaki are a “first rotation” crop and that this “dying forest” is not capable of

maintaining itself as a dense stand. It believes the trend is from dense softwood to medium-dense softwood and eventually to low-density softwood, with some hardwood. Because of this inevitable succession the aim of selection logging is to maintain these forests as “dense softwood stands in the very long term.” This is to be achieved by taking out the occasional tree, minimising disturb-

ance, and artifically planting softwood seedlings in the openings in the forest canopy created by the weeding out. This. programme was based on the theories of Dr P. J. McKelvey, who in the 1950 s and 1960 s studied the successional history and ecology of the West Taupo and Urewera

forests. Dr McKelvey saw as crucial to the history of these larger forests, which include Whirinaki. the impact of the last Taupo eruption in 120 AD. His theories are central to the question of whether logging is being conducted in Whirinaki to provide logs for the nearby Minganui village and sawmill, or for the benefit of the forest itself. He believed that areas which at present support . dense

lowland native softwood forests stayed free of tall forest for some 1200 years after the Taupo eruption. The 120 A.D. Taupo eruption ' was stupendous. When Mount St Helens erupted earlier this year it blasted out about four cubic kilometres of existing mountainside, but as this was mostly, dust the

eruption was not in fact energetic. The biggest eruption of modern times, Krakatoa off Java late last century, also released four cubic kilometres of material but as it was almost all magma (crude pasty mixture of mineral or organic matter) it was “quite energetic.”

These two eruptions place the 120 A.D. Taupo eruption in context. When Taupo erupted a minimum of 67 cubic kilometres of material from some 14 cubic kilometres of magma was released from the single vent on the present day Horomotangi reef in Lake Taupo. Ash from the eruption has been found as far away as the Chatham Islands. It was the biggest geological event science has so far been able to identify. Most of this material was spread in a radiaj pattern to about 80-85 kilometres in all direc-

tions. It laid down deposits from Rotorua to Taihape, and from Taumarunui nearly to Napier, in places up to 100 metres deep. The air flow from the blast created hurricaneforce winds. In front of the flow would have been a turbulent wall in which the vast majority of forests would have been vaporised. This wall would have had a high concentration of oxygen. Trees which somehow entered the flow in front of this wall, where there was almost no oxygen, were turned into charcoal and preserved. Dr McKelvey assumed from this interpretation that a vast area in the centre of the North Island became a wasteland for several centuries and then had no cover other than lichens and mosses for 1000 years. The dense forest now standing at Whirinaki, and elsewhere, he believed to be the first

tall forest that grew there after the 120 A.D. eruption. Mr Hackwell challenges that view. He outlines evidence that considerable patches of forest, and even wildlife, survived within that 85 kilometre radius. Tree size and age are not correlated. “There is little evidence to support the hypothesis that the dense softwood forests of the central North Island are evenaged or are a first crop,” he says. “A more realistic interpretation of the forest history following the Taupo eruption is that numerous remnants of forest survived (even quite close to the lake) behind topographic features which shielded them from the full effects of the flow. From these remnants forest regeneration would have occurred rapidly.” The theory of Mr Hackwell challenges the belief of the Forest Service that Whirinaki is a “dying” forest not capable of maintaining itself. If it is capable of maintaining itself, then neither selective logging nor articial replanting is needed to maintain it.

This new study must stoke up the fires of those onoosed to milling in Whirinaki.