UKTC Archive

Re: Tree Risk Communication

Subject: Re: Tree Risk Communication
From: Michael Richardson
Date: Jul 31 2020 10:57:21
Unfortunately David many people are not the least bit interested in risk or
comparing risk, they are scared of the very word risk.  I have had
countless examples of informing people their tree is very unlikely to fail
and the risk to people is low (well actually very low) and their response
is generally they cannot take any risk (often they are scared
their grandchildren will die).  I have had one municipality cut down trees
because self-shaded twigs were falling and the municipality could no longer
accept any risk.  I suggested that the risk of being injured at the
hockey arena is far higher than the risk from being injured by a tree; the
councillors still choose to cut the trees.

The language of risk is not easily understood by the public and most
municipal officials, it is one of the weakest points of using risk
assessment to assist in tree and urban forest management.  Assessment of
risk is not the problem, communication and understanding is.  I am sure
Julian Dunster as one of the world's experts on tree risk assessment and
protocols can speak to the issue more eloquently than I can.

This weekend is a long weekend here in Ontario, Canada and people will die
on the roads and drown, it is unlikely that a single person will be killed
by a falling tree or branch yet I have had people ask me about removing
their trees at the cottage to avoid any risk.

Michael Richardson B.Sc.F., BCMA
Ontario MTCU Qualified Arborist
Richardson Tree Care


On Fri, Jul 31, 2020 at 5:41 AM David Evans <> wrote:

Those of you who have to explain tree risk to civilians might find this

You're at greater risk from going on a 200 miles round trip in a car to
visit friends for a weekend than from branches or trees falling over a

I think this is such a relatable comparative risk that everyone accepts
without thought, and usually involves driving past trees, I'm using it in
the next version of VALID's Tree Risk-Benefit Management Strategies that
working on.

*A micromort is a one in a million chance of death

The risk from a 200 miles road trip = 1 micromort

The annual risk from trees = less than 1 micromort

For those of you who are interested in this kind of stuff.  The 200 miles
statistic is from Tim Harford's marvellous 'Cautionary Tales - The
Spreadsheet of Life and Death', available here.

It's about why the Value of Statistical Life is so important.  The tragic
tale of Clive Stone is a neat illustration of the folly of not using a
and a great skewering of populist politics.  Concerning trees, it explains
why the costs of tree risk assessment and management are a crucial part of
the risk equation.  And why the, 'If it saves one life' argument is an


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The UKTC forum is supported by Bosky Trees arboricultural consultancy and
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