Disclaimer: The views and opinions expressed in this article are those of the author and do not necessarily reflect the views of the Arboricultural Association.

Share this story


#ARBatwork #ArbMatters #EmbraceEquity #IWD2023 #PledgeLessPlastic #WomenInArb #WomenInTrees & 12 Faces of Arb 1987 storm 2 Rope 2018 2024 30 Under 30 3ATC 3ATC UK Open 50th annual AA AA award AA Awards Aboricultural Association Accident accreditation Addiction advice AFAG AFL aftercare AGM Agrilus Biguttatus aid air quality Alert Alex Kirkley All Party Parliamentary Group on Horticulture amenity Amenity Conference Anatomy Ancient Tree Forum Annual Awards Anthropology APF APF 2020 APF 2022 app APPGHG application Appointment apprentice apprenticeship Apprenticeships Approved Approved Contractor Approved Contractors ARB ARB Approved Contractor ARB Approved Contractors ARB at work ARB Magazine ARB Show arb training ARB Worker Zone ArbAC ARBatwork ArbCamp Arbor Day Arboretum Arboricultural Association Arboricultural Journal Arboricultural Student Arboriculture arborists Arbsafe Ash Ash Archive ash dieback Asian Hornet Assessments Assessors at atf ATO Australia Autumn Review award Awards Barcham Trees Bark Beetle Bartlett Bartlett Tree Experts bats Bats & Trees beetle Benjamin Zephaniah Best Student Award beyond ism Bill Matthews biochar biodiversity Biodiversity Net Gain biomechanical biosecurity Birmingham TreePeople BNG Book Prize Book Shop Booking Books Bookshop boundaries branch Branches brand Brexit bs5837 BSI Budgeting Tool bursary business Call for Abrstacts Call for Abstracts Call for papers Campout Canker stain of plane Canopy Climbing Collective carbon career careers Cavanagh CAVAT CCS Cellular Confinement Cellular Confinement Systems CEnv CEO Ceratocystis Ceratocystis platani chainsaw chalara charity Charles charter Charter for Trees Chartered Environmentalist chelsea Chelsea Flower Show City & Guilds Claus Mattheck climate climate change climber climbing code Cofor Colleges committees competition competiton conference Conference India Confor conifers conservation Consultant consultation Continuous Professional Development Contractor Contractor Focus Contractors Cornwall Cornwall Branch Coronation Coronavirus Coroner Council Countryside Countryside Code Countryside Stewardship Course for beginners COVID-19 CPD cross industry news Crown & Canopy Cryphonectria parasitica Cumbria DART Date for your diary David Lonsdale deadwood death debate Debt defra deployment Design Devon Director disease diversity DMM document donate dothistroma downloads draft Drought Dutch elm DWP EAC East Anglia ecology Economic Report economy Ecotricity education EFUF e-Learning Election elections Electricity Elm yellows Emerald Ash Borer England England Tree Action Plan England Tree Strategy English Elm environment Environment Act 2021 environmental EPF Equality equipment Equipment Theft Europe European Arboricultural Council European Forum on Urban Forestry European standards European Wood Pastures EUSTAFOR Event exeter Exhibitors Fall from Height Fatal Fatality felling Fellow Fellow Members Fera Field Trip Finance Fine firewood First Aid FISA flood flooding for Forest Research forestry Forestry Commission forests freelancers FSC Fund4Trees funding fundraiser fungal fungi Future Flora Futurebuild gardening GDPR General Election Geocells Gold Medal Gov.uk government grant grants Grapple Saws Green Brexit Green Infrastructure Green Infratructure Green Recovery Green Up Greneda relief Guarantee guidance Guidance Note Guidance Note 2 guide guides Hazard Tree Health heart-rot Heatwave Hedgerow hedges height Helliwell Help Henry Girling Henry Kuppen History HMRC HOMED Homeworking Honey Brothers honours Horse Chestnut HortAid horticulture horticulturists HortWeek housing HRH HRH Prince Charles HS2 HSE HTA ICF ICoP identification Immigration import industry Industry Code of Practice industry skills Infographic InfraGreen Initiatives Inspiration Institute of Charterd Foresters Insurance Intermediate Tree Inspection International Urban Forestry Congress International Women’s Day International Year of Plant Health invertebrates Investigating Tree Archaeology Conference IPAF Ips Ips typographus Irma irrigation ISA iso ITCC i-Tree IUFC IWD21 Jo Hedger Job Job Centre Plus job opportunity Jobcentre Plus jobs judgement JustGiving Karabiner Keith Sacre Kent Kew King’s Award for Enterprise Kit land-based Landsaping Landscape Institute Landscape Recovery Scheme Landscape Show landscaping Lantra law Leaf Minor Lectures legal legislation Letters Liability licence Local Authority Treescapes Fund London longevity LTOA Lynne Boddy Magazine Malawi Managegement Plan manifesto maple Mayor of London MBE Melbourne Member Benefit Member Survey Membership Mental Health mentor MEWPs Midlands Morphophysiology moth' motion Moulton College Myerscough NASA National Geographic National Hedgerow Week National Tree Safety Group National Tree Week NATO Natural England NatureScot Netherlands New Year’s Honours News NHS nominations Northern Northumberland Notice notification NTIS NTOA NTOC NTSG Nurseries oak 'oak Oak Processionary Moth Oak-boring Beetle obituary Observatree occupation of OHRG online opm Padua Papua parks parliament Perennial Pest Alert pests Pests & Diseases Pests and Diseases Petersfield petition Petzl photo Phytophthora Phytophthora pluvialis Pine Processionary Moth plan planning Planning Law Plant Health Plant Healthy planting Plantsman Plantsmans Choice Pledge Plumpton College policy poll Poster Power PPE practice Preston Twins Prince Charles Prince of Wales processionary Product Recall Professional Members prosecution Protect and Survive protected tree protection PUWER Qualifications Queen’s 70th Jubilee Questionnaire Quotatis ramorum RC Recruitment Red Diesel reference Reg Harris Registered Registered Consultant Registered Consultants Rehab Rememberance Day renewal REnvP Report Rescue research Research grant Resilience response results Retirement retrenchment review RFS rhs RHS Chelsea Flower Show Ride for Research Ride4Research rigging Rodney Helliwell rogue tree surgeons Royal Forestry Society RSFS Safe Working Practice Safety Safety Bulletin Safety Bulletins Safety Guides Safety Notice Saftey Salaries Sale school science Scotland Scotland Branch Scottish Branch SDG Accord security Seed Gathering Season Seminar seminars Share Sheffield Show Sierra Leone Site Guidance skills skills survey SocEnv Social Benefits of Trees soil soils South East South East Branch South West Speaker spotlight SRT SRWP staff Standards statement Stationary Rope Stationary Rope Technique statutory STIHL Stonehouse Storm strategy student Student Book Prize Student Conference Study Trip Sub-contractors Succession Successsion Supporter survey Sustainable Soils Alliance Sweet Chestnut sweet chestnut blight Sycamore Gap symposium T Level T Levels Tatarian maple TDAG Technical technical guide Technical Guides technical officer Technical Officers Technical Team Technician Members Technology Ted Green Telecommunications tender TG3 Thames & Chiltern The Arboricultural Association The Forestry and Woodlands Advisory Committees The Plantsman’s Choice The Queen’s Green Canopy The Woodland Trust Thinking Arbs Thinking Arbs Day Timbersports Tony Kirkham Tools top-handled chainsaws,Elcoat, TPBE4 TPO Trading Standards trailblazer training transport Tree Tree Care Tree Champion Tree Council Tree Fayre tree felling Tree Health Tree Health Week Tree Inspection Tree Life tree loss tree management Tree of the year Tree Officer Tree officers tree pathogen tree planning Tree Planting Tree Production Innovation Fund Tree Protection tree register Tree Risk Tree Shears tree species Tree Supply Tree Surgeon Tree Surgeons Tree Week Tree Work at Height Tree Workers Zone TreeAlert Treeconomics tree-felling TreeRadar trees trees' Trees & Society Trees & Sociey Trees and Society Trees and the Law Trees for Cities Trees, People and the Built Environment trust' trustee Trustees TrustMark Two Rope two-rope typographus UAG Uitlity UK favourite UK&ITCC ukas Ukraine UKWAS urban urban forest Urban Forestry Urban Tree Challenge Urban Tree Challenge Fund Urban Tree Cover Urban Tree Diversity Urban Tree World Cup urban trees UTD4 Utility Approved Contractors Utility Arboriculture Group UTWC vacancy Vanuatu VETcert veteran trees video Videos Virtual ARB Show volunteer voting VTA WAC Wales Wales Branch Warning Watering Watering Campaign watering solutions Watering Young Trees Webinar webinars website Wednesday Webinars Wellbeing Western Westonbirt Wharton White Paper WIA Witley Women Women in Arb women in arboriculture Womens Arb Camp woodland Woodland Carbon Code Woodland Carbon Guarantee woodland trust woods Work Work at Height Workshops World Environment Day World Fungi Day Xylella young Young Arboricultural Professional Young Arboricultural Professional Award young arborists Young People’s Breakfast Event Young Tree Aftercare Youth Programme zoo

Post-failure diagnosis: Anatomical pathology

Author:  Dambeza and Trouillet
Last Updated:  14/06/2024

Olivier Dambezat and Philippe Trouillet, Ceiba

When a tree falls in a public, visible and frequented area, the managers’ reaction is usually swift. Whether the failure caused damage or not, emotions run high and orders to diagnose the safety of nearby trees are immediate. On everyone’s lips, a single question: will they fall too?

De sedibus et causis morborum per anatomen indagatis ‘Of the seats and causes of diseases investigated through anatomy’ by Giovanni Battista Morgagni, first published in 1761.

De sedibus et causis morborum per anatomen indagatis ‘Of the seats and causes of diseases investigated through anatomy’ by Giovanni Battista Morgagni, first published in 1761.

In most cases, before any other intervention, the tree is cut down and its remains removed as quickly as possible. This rush is driven by practical and understandable concerns about freeing up public space, psychological concerns about calming fears, or, perhaps, political worries about judgement regarding the local management of trees. As a result, the investigation into the causes of the failure, which could guide the assessment of the mechanical condition of the remaining trees, will begin with a serious handicap: the lack of a corpse. And yet, both crime fiction and medical literature teach us that autopsies (from the Greek autopsia, meaning to see for oneself) are a formidable source of evidence and answers.

Without falling into anthropomorphism by comparing trees to people, the history of Western human medicine can be a source of inspiration for anyone interested in the development of tree diagnosis disciplines.

Until the 18th century, medical thought was dominated by a classification-based understanding of diseases. There were species of disease, just as there were species of animal or plant, and diseases had an autonomous existence, independent of the patient and his or her body. It was thanks to the systematic practice of autopsies and comparative work by a number of physicians at the time that the status of disease gradually changed. A new idea was developed that disease leaves traces in the tissues, and that it is these observable lesions that create the symptoms of the disease. This was the birth of a medical discipline that is still practised today: anatomical pathology. Morgagni, an 18th-century Italian physician considered to be the pioneer of modern anatomical pathology, believed that anyone who ‘has dissected or examined many corpses has at least learned to doubt. The others, who know nothing about anatomy and don’t bother to look into it, don’t have the slightest doubt.’

In those days, medicine was learnt at university and from books, a theoretical knowledge that limited contact with patients to the strict minimum. Life expectancy was 24.7 years (the figure for France in 1740).

Illustration of a hypothetical damage pattern on a Second World War bomber. Based on an unillustrated report by Abraham Wald (1943).

Illustration of a hypothetical damage pattern on a Second World War bomber. Based on an unillustrated report by Abraham Wald (1943).

Illustration of a hypothetical damage pattern on a Second World War bomber. Based on an unillustrated report by Abraham Wald (1943). Post-failure diagnosis of a plane tree in Var, France, April 2022.

Post-failure diagnosis of a plane tree in Var, France, April 2022.

You are missing what is missing

Why should we pay attention to fallen trees? Isn’t it more interesting to examine those which remain standing?

As early as the 17th century, William Harvey, an innovative English physician, wrote that ‘The examination of the corpse of a single man who has died of a chronic disease is more useful to medicine than the dissection of ten hanged men.’ Anatomical pathology has made it possible to identify the traces of disease within the body, and each anatomical alteration corresponds to a functional alteration. After death, the pathological changes remain visible and can be observed, described and analysed.

By making it possible to think calmly and methodically about the visible symptoms, work on recently failed trees helps to mitigate the influence of numerous biases when diagnosing standing trees: anchoring bias (remaining focused on the first impression), pessimism bias and defensive arboriculture (‘you never know’), etc. But the main bias that post-failure diagnosis tackles is survivor bias. This bias consists of over-estimating a phenomenon by focusing on successful cases and ignoring all the others.

A famous example comes from the Second World War, when surviving aircraft returned from missions. After statistically analysing the location of the impacts of enemy fire on the fairings, American engineers proposed adding shielding to the areas most affected (for weight reasons it was not possible to shield the whole aircraft). But a mathematician, Abraham Wald, stopped them, arguing that if these planes had returned to their home base, it meant that they could continue to fly when hit at these points. Those that had been hit in other places were not included in the statistics because they had disappeared. The areas least affected on the surviving aircraft were therefore probably the most critical. He recommended shielding those areas, which was done. Without assuming that the war was won thanks to Wald, we can nevertheless see here that focusing on the survivors can lead to real diagnosis errors: by overlooking what is not there, ‘you are missing what is missing’.

An opportunity to learn

In arboriculture, as in military engineering, being able to analyse only intact subjects will not allow us to understand what probably differentiated the one that fell. Every tree failure should be an opportunity to learn.

However, in a post-failure diagnosis, two conditions are necessary for this observation experience to become a learning experience. The first step is to understand the symptomatology, which requires a number of parameters to be systematically and factually recorded. At this stage, the most common error is again a type of survivor bias. Since the absence of a symptom is itself a symptom, it would be a serious mistake to overlook, for example, the lack of adaptations (reinforcing wound wood, adaptative growth, buttresses, etc.) in the failed subject. The second condition is that we are dealing with a predictable failure that could have been anticipated. As in medicine, a certain number of failures are in fact associated with phenomena that have no visible symptoms (or at least, as these symptoms are not yet known or identified, they can’t be detected). In these cases, we probably can’t draw much from our observations, other than to confirm this occasional unpredictability.

In the field of life sciences, and particularly in arboriculture, there are undeniable difficulties in meeting the conditions for the development of real expertise as identified by the psychologists Kahneman and Klein: 1. A stable environment (regular, always behaving in the same way); and 2. Sustainable practice with quick, unambiguous feedback. If it doesn’t solve everything, the post-failure diagnosis could compensate a little for the lack of quick feedback (trees are a long-term process) by making the situation clear: there’s no ambiguity – it’s fallen.

The practice of post-failure diagnosis

For several years now, we have been systematically studying the failed subjects we encounter, sometimes by chance, sometimes following instructions from managers. The remains of the trees are cut up, and moved if necessary, for a meticulous process of observation, probing and sometimes dissection that can take several hours, until the phenomenon is understood. In the vast majority of cases, we are able to associate failure with a clear symptomatology. Once the symptoms have been identified, the rest of the diagnostic investigation is usually a simple matter: find any similarities in the surrounding subjects that are still standing and whose situation is of concern.

In nine years of activity and several dozen post-failure diagnoses, we have come across a few cases that could probably not have been anticipated (gale force winds, summer branch drop, etc.). These exceptional cases do not generally call into question the mechanical resistance of neighbouring trees. The vast majority of the trees studied showed a combination of symptoms, more or less obvious or easy to observe, which clearly explained the failure.

A final comment concerns the time lag between tree failure and post-failure diagnosis. As Morgagni pointed out in his time, an autopsy is of no use if we are unable to detect changes that deviate from the norm and are not due to post-mortem decomposition. Even more than disease, death alters tissues, and trees that failed long ago will no longer have much to offer the diagnostician’s eye.

In conclusion, if our aim is to make an accurate diagnosis that will enable the preservation of trees, we could also draw inspiration from Laennec, whose anatomical pathology-fuelled conception of disease led to the invention of the stethoscope, a tool that would pave the way for what could be called the autopsy of the living.

Philippe Trouillet

Originally a climbing arborist, then a consultant and trainer, in 2015 Philippe Trouillet founded the Ceiba consultancy and training centre in France – www.ceiba-conseil.com. He now specialises in clinical mechanical assessment and tree risk assessment.

Olivier Dambezat

Olivier Dambezat is Ceiba’s CEO. After a degree in philosophy followed by an artistic career, he has been associated with Philippe since 2018, working on the development of various subjects in amenity arboriculture. Philippe and Olivier will be presenting on ‘Mechanical features: towards new methods of building an observation-based likelihood of failure’ at the Association’s conference in September.


Drénou, C. (2022). Slow Tree : apprendre à respecter la lenteur des arbres. La lettre de l’arboriculture 106. May/June, SFA.

Foucault, M. (1983). Naissance de la clinique. Une archéologie du regard médical. Presses universitaires de France (PUF).

Grmek, M.D. (dir.) and Risse, G.B. (1997). La synthèse entre l’anatomie et la clinique. In: Histoire de la pensée médicale en Occident, Vol.2: De la Renaissance aux Lumières. Seuil.

Kahneman, D., and Klein G. (2009). Conditions for intuitive expertise: A failure to disagree. American Psychologist 64(6): 515–526.

Laboisse, C. (2020). Laennec, formation et destin d’un médecin, de l’anatomie pathologique au stéthoscope. mediaserver.univ-nantes.fr (accessed 20/3/24).

McRaney, D. (2015). Missing what’s missing: How survivorship bias skews our perception. www.ted.com/watch/tedx-talks

Tremblay, C. (2015). Compte-rendu: Naissance de la clinique de Michel Foucault. Aspects sociologiques 22: pp. 169-180.

Trouillet, P. (2022). Les biais de diagnostic. La lettre de l’arboriculture 105. March/April, SFA

Vallin, J. (1989). La mortalité en Europe de 1720 à 1914: tendances à long terme et changements de structure par sexe et par âge. In: Annales de démographie historique. Le déclin de la mortalité: 31–54.

Wald, A. (1943, 1980). Reprint of A Method of Estimating Plane Vulnerability Based on Damage of Survivors. www.semanticscholar.org (accessed 20/3/24).

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.