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Leith Knowles and the radiata calculator

Piers McLaren, New Zealand Tree Grower November 2018.

The radiata and Douglas-fir calculators were the brain-child of the late Forest Research Institute researcher, Leith Knowles. Many of us knew Leith well, as he was a great fan of the NZFFA. The author was a work colleague and close friend of Leith and I thought it would be useful to give some background to the creation of the calculators which were featured in an article in the August Tree Grower.

Leith Knowles knew he was dying and feared that knowledge so painstakingly assembled from a lifetime of silvicultural research would be lost. Therefore, even when in his last days and wracked with pain, Leith would force himself to his office to tidy up the model which he privately called ‘My Honey’, and which came to be known as the Radiata Pine or Douglas-fir Calculator. His main helpers were Lars Hansen, a farmer from Denmark, and Mark Kimberley, a brilliant Forest Research statistician.

The calculators were based on the discovery that a lot of the detail in our existing forestry models was unnecessary. You could get more or less the right answer by simplifying or even by omitting some factors. It had taken thousands of scientist-years to collect and analyse the data to create the complex equations that drove the models, but having done that, and discovered which ones were important, you could use an ordinary Excel spreadsheet to make them work. Many people, including farmers, could handle spreadsheets. The idea was to have simple, easy-to-use inputs, although the outputs could be very detailed and pushed the boundaries of what was possible in the original Microsoft programme.

A tax return

Leith faced considerable opposition to his work. Firstly, it was scorned by industry players because it contained agro-forestry which placed it almost in the category of hobby-farming. In his later years, Leith was equally dismissive of agro-forestry, even though he had spent a lot of his life working on the subject. It was included in the radiata calculator merely to get NZFFA support and to secure funding. Secondly, although the calculators were very sophisticated, they were not good enough to answer many of the things which were important to large forestry companies. Thirdly, the Forest Research Institute needed to protect its intellectual property and a significant source of its funding and Leith wanted to make the information available at the grassroots level. Therefore, he insisted that a subscription to the NZFFA would allow farm foresters a back-door route into ownership.

It seems that many of these objections were unjustified. The calculators are indeed good enough to be used by large companies in day-to-day decisions − often a rough and quick answer is all that is needed. If needs be, the far more sophisticated cousin, Forecaster, can work alongside them. Another consideration is that many of those scientist-years of research on which the calculators were built were paid for by the taxpayer. The general public deserves something free in exchange for all their taxes.

Useful workshops

To promote his calculators, Leith organised a series of well-attended workshops around the country. He paid for me to attend these workshops as an assistant, although I hasten to add he could easily have handled it all on his own. In retrospect, it seems that Leith hoped I would adopt his project and ensure the survival of his brain-child after his death. He need not have worried. The calculators are in regular use throughout the country and are the backbone of the Emissions Trading Scheme. Attempts have been made to duplicate their success with many other species, but these have all foundered mainly due to the fact that other species have insufficient data to support them.

There was once a suggestion to incorporate a photograph of Leith within the computer program, together with a short epitaph. I thought that this was an excellent idea and would have been far more meaningful than any version carved in stone. Sadly, the suggestion went nowhere. Having said that, I have full confidence that the calculators will survive, mutate and multiply for decades to come. Leith’s legacy will live on.

Piers McLaren is a well-known and respected forest researcher.


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