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Paper Shows Flaws In Beech Scheme Model Software

Press release - 10 February 2000

For immediate use


Beech forest growth model software used by the Minister of Forestry to judge that the beech scheme was unsustainable has been assessed by a University of Canterbury Academic, and a peer-reviewed scientific journal paper describing the results of the assessment has been accepted for publication. The paper shows that the model software is severely flawed, and misrepresents the processes at work in the forest following low-impact harvesting.

The paper was written by Dr Euan Mason, a Senior Lecturer in Forestry at the New Zealand School of Forestry, University of Canterbury, and a skilled modeller. It was reviewed by a New Zealand forest modelling expert, a forest modelling expert from overseas, and a New Zealand-based forest ecologist. It was also vetted by a number of highly qualified academics at the University of Canterbury. All agreed that the reasoning was sound, and that the paper should be accepted for publication in a scientific journal with only minor modifications. Peer-reviewing is an essential part of the scientific process that involves academics critically reviewing the contents of papers before they are accepted for publication in scientific journals. If a paper is found to be lacking in logic, poorly based on current knowledge, to have flaws of procedure or to be of no consequence, reviewers have the power to recommend that it be rejected. For the paper to be accepted after rigorous reviewing by experts in forest modelling indicates that it is well-founded.

The model software that the paper criticises was constructed by Dr Murray Efford, of Landcare Research, and was widely distributed to the public via the world-wide web from Landcare Research's web site. It was crucial in forming the views of conservation groups, some ecologists who have claimed small-scale harvesting would profoundly affect forest ecology, and the government prior to the cancellation of Environment Court hearings on the beech scheme. For instance, on the 22nd of December Hon Peter Hodgson, the Minister of Forestry, responded to criticism of this action by saying in parliament:

"The member can laugh and scoff. He can go to the net and play with buttons himself, and what he will find out is this. If one logs the forest, sooner or later--and there is debate about whether it is sooner or later, that much I will concede--the character of the forest changes for ever." (Hansard B09-3, December 22 1999)

Dr Mason, who has been publicly critical of Efford's model, says that normally scientists would not engage in so public a debate about each others' work, but that in this case the political and public impact of the model software was so great that he could not refrain from speaking out. "The model software encourages naive users to make unrealistic assumptions about the behaviour of beech forest", he says. "In addition, the software purports to make predictions over centuries, and this type of model cannot reliably work over such long periods. It was so widely distributed and had such a large impact that speaking out became a matter of integrity." A second version of the model software contains some revisions, but is just as flawed in many respects as the version that influenced policy, he says.

Implications of the model software being flawed are large. The Minister used the software as his main justification for stopping an Environment Court hearing that would otherwise have come to a well-informed judgment about whether or not the beech scheme was ecologically sustainable. The model software's predictions of grossly altered forest structure following small-scale harvesting were also used by some ecologists as a basis for their assertions that harvesting might adversely affect wildlife.


Dr Euan G. Mason Ph: 03 3642584 (work), 03 3482671 (home), 03 3642124 (fax) email:


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