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David Lonsdale

Author:  Jim Pratt
Last Updated:  12/06/2024

David Lonsdale started his training as a naturalist at the age of eight, in the East End of London where he was born in 1950. He made observations of the wildlife and plants he found in the bombed-out gardens, that, in the 15 years after the war, had evolved their own peculiar environment.

David in his element: examining an insect in a modern beech stand planted in a Romano-British field in the Sussex Downs, April 2010. (Photo: Jim Pratt)

David Lonsdale in his element: examining an insect in a modern beech stand planted in a Romano-British field in the Sussex Downs, April 2010. (Photo: Jim Pratt)

As he explained to me, he had the great fortune to be taught by the same lady teacher right up to O Level, and one suspects that she understood this quiet, reflective and rather singular little boy who noticed everything around the school, and asked incessant questions about the names and functions of everything he saw.

At the age of 18, with excellent A levels, he entered the University of Southampton. As his sister related, ‘On being accepted there he immediately wrote to the landlady on the university’s approval list that he would need to have an electrical light socket so he could plug in a lamp to keep his stick insects comfortable in their container. The following afternoon David’s mother received a telephone call informing her that the landlady had turned up at the university in a great state telling the housing contacts that she could on no account accommodate this young man or his stick insects. However, the principal said they would be glad to provide a place “in halls” for both David and his stick insects.’ From Southampton he moved to Manchester University where he completed his PhD into a disease of potato. What was important about his recollection of Manchester was the very affectionate relationship he had with the matronly landlady of his digs; she was Armenian and despite the fact she had a hard life, I suspect she mothered him.

When he completed his PhD in 1975 jobs were hard to come by, but he applied for a temporary post at Forest Research, Alice Holt, and was seconded to Surrey University at Guildford to complete an existing study into beech bark disease (BBD). In this, scale insect, Cryptococcus fagisuga, colonises the thin bark of young beech trees, being able to penetrate the thin rhytidome into the living phloem below from which to obtain nutrients. The holes made allow the infection of the phloem and cambium by a common pathogen: Nectria ditissima. The purpose of the research was to try to understand environmental and cultural factors that threatened crops of planted beech in Britain, and in the USA in naturalised stands. To that end, the USDA Forest Service sent its top pathologist to Britain for a year’s sabbatical to work on BBD. This proved to be the single factor that transformed David from an agriculturalist and entomologist into a committed forest pathologist. In the words of the American pathologist Dr David Houston:

‘I first met David in 1975 when I was an exchange scientist from the US Forest Service to the Forestry Commission. As a forest pathologist, I was there to study aspects of beech bark disease (BBD), and in the beginning was introduced to the disease in beech plantations of southern Britain by John Parker. When John was seconded to Zambia, David (a fresh PhD who had done his research on potato diseases!) was hired to assist me. BBD was as new to him as plantations of European beech were to me. So, for nearly a year, we worked closely together exploring many aspects of the disease – some of which we would have not been able to do under normal circumstances.

‘One example: we found that the bark of some beech trees had black patches of the fungus Ascodichaena rugosa, some extensive enough to cover most of the lower stem. We found that the beech scale was unable to infest bark colonised by Ascodichaena. We also found that the upward spread of the fungus resulted from the activity of a snail, Clausilia sp., that fed on Ascodichaena and then deposited spores in its slime trail over radulated tissue. Unfortunately, upper crown branches are usually scantly colonised, remain susceptible to BBD and even those trees with boles heavily colonized by Ascodichaena eventually succumb.

‘The year 1975 was the beginning of the “500 year drought” and in the forests where we worked some beech trees were becoming chlorotic. Some of this we attributed to BBD, but some trees were not affected by the disease. And this began the long-term investigation by David and Jim Pratt of lime-induced chlorosis attributed to early Roman agricultural practices on these soils underlain by chalk.

‘David participated in the IUFRO Beech Bark Disease Working Party Conference I led in the US in 1982. He not only presented several papers on BBD, but also edited the European contributions. I had the opportunity to show him BBD in natural forests of American beech … quite different from that in the plantations of Britain!

‘We kept in touch over the many years, and last May spent a wonderful day together in Marden Forest recounting our early days there. It was such a delight!’ (Dave Houston, 14th April 2024)

The bark thickness was not sufficient for the scale insect to penetrate efficiently in old trees, and the period of maximum danger was while the trees were still relatively young.

This period of research with an ecologist as experienced as Dave Houston taught David Lonsdale important lessons about observing and learning about the interactions that occur within all the parts of long-lived, variable trees (leaves, twigs, branches, stems, roots, and of living and dead wood), and his worth as an holistic tree scientist expanded.

When that work came to an end, and for a brief period after I had finished my work on Sitka spruce and was awaiting a transfer to North Scotland to manage commercial felling, I helped David Lonsdale observe and describe drought damage to large exposed beech trees. This took us all over southern Britain, often to the country houses of the rich and the famous, from the royal family to senior, retired generals and members of the House of Lords. David treated them all with the same straight-forwardness that was his hallmark. And some of them were very peculiar and demanding indeed. One question predominated: were droughted old beech safe? This stimulated him to think about the processes of ageing in large, often old trees and he became familiar with the need to think holistically about all the factors that determine the resilience of that wonderfully engineered natural behemoth that is a full-grown tree, and the limitations of its growth mechanism, physiology, disease resistance and stability. And, as in anything he studied, he applied himself to detail and to first principles, never accepting as correct a theory that had not been tested in detail.

It was at this point in his career that our paths split and I was posted to commercial timber harvesting in the Great Glen: a job of such profound danger that I had little time to consider my earlier work with David. And I remained in Scotland (where I live now) so was not involved in the remainder of his career at Alice Holt or after retirement when he changed his emphasis to issues of conservation of trees and legal disputes.

But what is clear is that the selection of David as the author of that vade mecum of all those involved in tree safety and conservation, namely the 388-page Principles of Tree Hazard and Management which he wrote and published with the Department of the Environment, Transport and the Regions and the Forestry Commission, was nothing short of miraculous Every statement, every picture in that book is David’s work, as is its brevity and simplicity of style, and the huge amount of field and laboratory work which underpins every statement within it. That laboratory work also had international roots, from David working with Alex Shigo in the north-east of the United States who for years demonstrated the need for clinical examination by sectioning failed branches or stems, to the mathematical structural modelling of the East German medical scientist Claus Mattheck who turned his knowledge of structural failure in skeletons to that of trees in his important book The Body Language of Trees: A Handbook for Failure Analysis. There are very few people in the world who could achieve, largely alone, David’s monumental investigation into tree safety, starting almost from first principles, and then make it generally and easily available to all who need or want to know about the world’s largest and most long-lived organisms.

David took early retirement from the Forestry Commission around the millennium, and as far as I am aware devoted himself to promulgating issues of the conservation of trees (and indeed, of all life, especially of insects). Managing old trees so that they could remain as safe structures while providing habitat for other creatures became a key issue with him, and may have been the driving force behind the numerous field days and lectures he gave, in his own time, to the informed or general public. That these were effective is clear in the outpouring of (dare I say) love and affection shown in the comments of numerous citizens on his untimely and dreadful death in April 2024.

His unfailing modesty, good manners, concern for all life and encyclopaedian knowledge are a mark of humanity at its best. As was his laugh, which is how I will remember him, my best pal for 55 years.

Jim Pratt MBE, Scottish Borders

Tributes to David have come in to the Association from far and wide. We will include as many as possible in the next issue of the ARB Magazine.

This article was taken from Issue 205 Summer 2024 of the ARB Magazine, which is available to view free to members by simply logging in to the website and viewing your profile area.