When a tree risk assessment matrix is the same as adding up hopeless hedgehog cakes

2021-09-21 6:25 PM | Admin (Administrator)

Do 5 hopeless hedgehog cakes = 1 fantastic hedgehog cake?

Tree Risk Matrix | Adding up 5 hopeless hedgehogs cakes to make one great hedgehog cakeOf course 5 one star cakes don't add up to 1 five star cake.

The reason why is you can't apply mathematical rules to qualitative ordinal ranks or scales when assessing tree risk - or assessing any risk, for that matter.

It's why having to suffer the film 'Sex in the City II' five times doesn't have the same value as enjoying 'The Godfather' once.

Similarly, applying mathematical rules to ill-defined words and saying things like High × Low = Medium is just as crazy as adding up hopeless hedgehog cakes when managing and assessing tree risk.

Risk experts know this well, but in the world of tree risk there are plenty of examples where hopeless hedgehog cakes are being added up.

The most recent half-baked crime against risk and reason has been brought to our attention by concerned Highways Managers and Arborists in the 'Lantra Technical Award in Tree Inspection for Highways Workbook.'

Lantra Tree Inspection for Highway | Tree Risk Matrix - David Down & Jeremy Barrell

Here, qualitative ordinal ranks or scales are added up, just like hopeless hedgehog cakes, in what the workbook calls a tree risk matrix (it's not a matrix, it's a table) to work out 'THE RISK'.

The authors of the 'Lantra Technical Award in Tree Inspection for Highways Workbook' are David Dowson and Jeremy Barrell.*

We recently had a discussion with Dave Dowson about adding up these hopeless hedgehog cakes to assess and manage tree risk on the UKTC discussion forum.  In the interests of balance, you can catch Dave's response below.  Our reply to that follows.  The links also give you access to other comments in the discussion.

Dave Dowson's response

Our reply

*The risk matrix (sic) is also peculiarly noteworthy because Jeremy Barrell has published that he thinks there are only two likelihood of occupancy zones.  High and Low.  Here, he has three targets, or likelihood of occupancy zones.  High, Medium, and Low.