Page From the Past – Ruahine Ranges Erosion is Natural

by Tony Orman

In 1989 Dr. Patrick J Grant a hydrologist and botanist from Hawkes Bay, published a paper entitled “A Hydrologist’s Contribution to the Debate on Wildlife Management”.
In it he recalled back in 1955 with advice from Peter Logan of the NZ Forest Service, Patrick Grant had prepared a report for the Hawkes Bay Catchment Bard on wild animal control in the upper Tukituki Basin of the Ruahine Range. 
“At that time I accepted the conventional philosophy that at the head of the Tukituki River is not natural erosion – it is very definitely accelerated erosion or induced.”
He then concluded that “firstly we must gain the necessary control of the (wild) animal populations.”
The same philosophy had appeared on official brochures of the NZ Forest Service and the Soil Conservation and Rivers Control Council.
But historical events made him wonder about the validity of conveniently blaming wild animals for erosion
Bishop Colenso
Ten years later in 1965, Patrick Grant produced a brief historical study of the Tukituki River and in it quoted observations from the diary of missionary/explorer William Colenso who in the 1840s crossed the Ruahine Ranges – almost half  century before red deer were liberated.
“Colenso’s vivid descriptions of severe, active erosion in 1845, made inescapable the conclusion that much of the scarring we see today on the Ruahine Range had its origin before the time of extensive European settlement and the introduction of wild animals,” wrote Patrick Grant.
By 1969 he was convinced that “exotic feral animals did not cause land instability”.
So he researched it delving back in history finding that the Ruahines and elsewhere (e.g. Ureweras had been subjected to four severe periods of erosion since the 13th century.
“My ideas crystallised in 1983 by the results of a systematic study in the upper Waipawa Basin (of the Ruahines),” he related.
By 1985 Patrick Grant was able to show there had been at least seven other periods of accelerated erosion since 180AD.
“These were long before even Polynesians and their animals had arrived in New Zealand.”
Climate cycles had been the cause of erosion.
Patrick Grant identified severe drought periods such as 1909 to 1915 when there were several dry/drought years culminating in the 1914-15 mega-drought that “affected high-altitude forests more abruptly and more severely than the impact of browsing animals.”
Within a few years, stressed giant forest trees succumbed to the effects of the prolonged drought. 
The Forest Service, Catchment Board and Forest and Bird Society blamed the dead giant tree spars on wild deer and possums. It wasn’t – it was natural climate cycles involving drought.
“The present period of increased erosion and alluviation is primarily the consequence of atmospheric warming and the bigger rainstorms and floods it brings. Browsing animals have not contributed significantly,” said Dr Patrick Grant in his paper’s summary.

© Red deer – not the cause of natural erosion in the Ruahine Ranges

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6 Responses to Page From the Past – Ruahine Ranges Erosion is Natural

  1. Andi Cockroft says:

    Arguing with people who have already made up their minds is a waste of time and energy.
    I well remember appearing before a subcommittee regarding erosion of sand dunes being caused by the lack of grass and insisting it had to be replanted – as it happens with non-native Ammophila Arenaria (Marram Grass). Indeed the “expert” witness called to give evidence was none other than a retired police sergeant with no ecological credentials whatsoever. Nonetheless, the subcommittee willingly accepted this unqualified “evidence” and ignored highly-qualified trained specialists simply because it met their desires.
    Our own experts argued that sand dunes in the area are naturally living bodies with dunes constantly moving driven by the prevailing winds. As sand is removed, it is replenished by windblown sand from further afield.
    Understanding the motives of the subcommittee it became clear. Houses that had been recently built by bulldozing the dunes were being inundated by windblown sand whipped up from the dunes. Planting an exotic grass slowed the sand progression and stopped the problem for those homeowners who had bought houses built in inappropriate places.
    Those dunes now planted, 20 years on, are a shadow of their former self, having lost much of their height.

  2. Dave Richardson says:

    Tikokino was my home village and so the Ruahines were on our back door and although deer were spotted early on they did not cause any erosion. The tales of the erosion were told in many publications and by old shooters and explorers of the time.

  3. "Amateur Botanist" says:

    I hunted an area in the late 1950s in the Southern Ruahines. Deer were numerous but bush was in fine fettle. Regeneration was strong with unpalatable species like horopito (pepper wood) taking over from palatable. So with a reduction in palatable species was Nature’s way to “control” deer numbers. The same thing would have happened with moa. Nature knows what she is doing. DOC doesn’t.

  4. Lewis Hore says:

    Try to convince DoC and Forest and Bird of these findings.

  5. "Amateur Ecologist" says:

    “Amateur Botanist” is right on the button. The more Man interferes the more disruption to the food chain. For instance 1080 knocks out 80% plus or minus of rats. So Nature in her wisdom says rats are down, food is abundant – less mouths to compete with for 20% survivors – lets step up breeding to compensate. So breeding accelerates and a population explosion occurs. The momentum carries the explosion past the original rat population and up and up. So 3-4 years later, there are at least three times the original number of rats. DOC knows the research is there to show what happens post-1080 aerial drops. It does not end there. Stoats whose principal prey is rats, have more food (rats) so they breed like crazy. A stoat plague follows the rat plague. Ecological mayhem, thanks to DOC’s stupidity or is it deviousness to keep the 1080 gravy train, with vote money, jobs and empires, going?

  6. Rex Gibson says:

    Sadly it does not fit DoC’s funding agenda. They are the Department Of Chemicals and will tell whatever lies are necessary to continue to be funded as such.
    Tim Neville

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