UKTC Archive

Re: Tree hazard potential assessment study RISK AVERSITY?

Subject: Re: Tree hazard potential assessment study RISK AVERSITY?
From: Wayne Tyson
Date: Sep 13 2018 00:14:56
*Advice From the US*

https://www.13newsnow.com/article/weather/worried-about-florence-knocking-trees-on-your-home-heres-what-to-do/291-593143179

Wayne

On Wed, Sep 12, 2018 at 2:54 PM Wayne Tyson <wt750mv@xxxxxx.com> wrote:

Hear, hear!

Wayne

On Wed, Sep 12, 2018 at 2:31 PM Michael Richardson <
richardsontreecare@xxxxxx.com> wrote:

As usual, Julian has provided a great deal of wisdom.

Perhaps Julian could write about trees, risk and the law!
Oh yes!
Arboriculture and the Law in Canada
  Tree Risk Assessment Manual
  Tree Risk Assessment in Urban Areas and The Urban/Rural Interface
Trees and the Law in Canada



Michael Richardson B.Sc.F., BCMA
Ontario MTCU Qualified Arborist
Richardson Tree Care
Richardsontreecare.ca
613-475-2877
800-769-9183

  <http://www.richardsontreecare.ca/images/Tree_Doc_logo_email.png>



On Wed, Sep 12, 2018 at 3:06 PM Koeser,Andrew <akoeser@xxxx.edu> wrote:

I believe this is the article mentioned by Julian.

http://joa.isa-arbor.com/request.asp?JournalID=1&ArticleID=3341&Type=2

(It will prompt you to open as a pdf).

Andrew

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info <
uktc-request@xxxxxx.tree-care.info>
On Behalf Of Julian Dunster
Sent: Wednesday, September 12, 2018 2:45 PM
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: Tree hazard potential assessment study RISK AVERSITY?

Wayne

Perhaps you missed some concepts in the underlying discussion here. Risk
assessment informs risk management.

Risk assessment and risk management are tied to the legal concepts of
standard of care. The standard of care under English Common law (and the
same or similar concepts underpin US law) deals with what is expected of
the 'reasonable person' and that has always been defined by the court
system.

Others have noted that terminology is important. Risk is not the same as
hazard. Risk assessment of trees is, and always will be, a subjective
exercise based on professional judgement. It is not possible to attain
perfection in tree (or any other field of enquiry) risk assessment or
risk
prediction. It is possible, regardless of which tree risk assessment
process is used, to accomplish a 'reasonable' assessment based on
accepted
industry standards that provides an opinion about the level of risk
likely
in typical operating conditions. We do not and should not attempt to try
and provide a tree risk assessment opinion that accounts for adverse
weather conditions such as major storms. All bets are off once we get
into
extreme weather patterns and it is well known that healthy trees with no
defect can and do fail in such conditions.

All of which means we have limits of what can or cannot be accomplished,
and chasing perfection is most likely to be an enormous waste of time of
money that is entirely disproportionate to the actual risk involved. For
the record, check my article in the Journal of Arboriculture and Urban
Forestry a few years back where I document the actual number of
fatalities
and injuries associated with trees in various parts of the world. I
don't
have the exact data as I am in Sweden right now teaching tree risk
assessment and I do not have access to the full citation. In the UK
fatalities area around 6 or 7 a year. In the US that number is around
100
to 150 a year reflecting the many more adverse weather conditions found
across a much larger land base. In Canada it is around 2 to 3 a year
reflecting the fact that we do not suffer the extreme weather conditions
commonly seen in the US. I expect climate change may alter those numbers
over time.

Perhaps Michael R can dig it up and add it to the debate for your
information.

jd





On Behalf of Dunster & Associates Environmental Consultants Ltd.

Dr. Julian A. Dunster R.P.F., R.P.P., ISA Certified Arborist, ASCA
Registered Consulting Arborist, PNWISA Certified Tree Risk Assessor #1.
ISA Tree Risk Assessor Qualified.

Honourary Life Member International Society of Arboriculture (ISA) and
PNWISA

North American Distributor for Rinntech
Canadian distributor for Air Spade

email: jadunster@xxxxxx.com


www.dunster.ca


On Wed, Sep 12, 2018 at 8:02 PM Wayne Tyson <wt750mv@xxxxxx.com> wrote:

Michael,

That's my point. Trees "owned" by governmental agencies are, as I
said,
*supposed* to be managed, and in my view, should be managed
intensively (whatever that means).

Wayne

On Wed, Sep 12, 2018 at 10:43 AM Michael Richardson <
richardsontreecare@xxxxxx.com> wrote:

I am very interested in exactly where this place is:
The bottom line is that failed trees that are supposed to be under
intensive management by tree professionals are almost constantly in
the news here in the US

Where are these intensively managed trees?


Michael Richardson B.Sc.F., BCMA
Ontario MTCU Qualified Arborist
Richardson Tree Care
Richardsontreecare.ca
613-475-2877
800-769-9183


<
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On Wed, Sep 12, 2018 at 1:32 PM Philip van Wassenaer <
pwassenaer1022@xxxxxxx.com> wrote:

What is imminent? If you can look at it and tell me it will fail
within the specified time frame and the timeframe is very short,
then it might
be.

I don’t think we can do this in all but a very few cases.... so
trying
to
have us perform at this standard is suicide...

You also need to be careful with the proper use of the term
"hazard"
...you can only really apply this term to high or extreme risk
situations...otherwise they are just low risk but NOT low hazard.

I think the trees are in the news there more often because of the
huge risk aversion caused by a ridiculous frequency of litigation
in
the US.
Otherwise the risk of injury or death from trees there is probably
as
low
as it has been reported in other places like the UK or
Australia...

If the risk of injury or death is so low it probably falls into
the broadly acceptable range and there would be little to no use
in
gathering
more data...or even more intensive tree management for that
matter. If
the
risk is in the range of 1/10,000,000, what amount of investment
would
you
have to make to get even lower than that?

Cheers,


Philip van Wassenaer, B.SC., MFC
Principal Consultant
Urban Forest Innovations Inc.
Mississauga, Ontario, Canada
www.urbanforestinnovations.com



-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info [mailto:
uktc-request@xxxxxx.tree-care.info] On Behalf Of Wayne Tyson
Sent: September-12-18 12:15 PM
To: UK Tree Care
Subject: Re: Tree hazard potential assessment study RISK AVERSITY?

David,

I'm concerned only with accurately sizing up the tree's condition
before
considering the "risk." Mainly, what is the tree's condition, and
does
its
condition represent either an "imminent" potential for failure or
a
trend
in that direction. That is, are the conditions observed trending
toward further degradation or increasing or maintaining a stable
state.

The whole concept of risk assessment seems like an exercise in
statistical
probabilities with an icing of terms like "target" on it. To me,
it's
more
important to assess the tree's condition and its trend first, then
decide
whether it's likely, for example, to kill someone when it does
fail. I
look
at what has happened, then back up through the failed tree's
history to
see
whether or not there were signs of the hazard present before the
failure.
So, far, there have been signs aplenty that any tree person worth
his
or
her salt could have detected.

If the tree's in a forest, there's no expectation of "safety." I
take
my
chances in a forest. In an urban setting, trees are subject to all
sorts
of
mauling about (from "birth" to death) that increases their hazard
potential. If the problems are increasing, trending toward getting
worse
instead of better, proactive measures may be indicated if nothing
can
be
done to turn around the trend.

The bottom line is that failed trees that are supposed to be under
intensive management by tree professionals are almost constantly
in the news here in the US, and I gather that the UK is not
immune. Is
reducing
the number of such failures a worthy goal? Would gathering data
that
could
be usefully fed back into management worth doing?

Wayne

On Wed, Sep 12, 2018 at 1:19 AM David Evans
<david@xxxxxxxxxxxxxx.com>
wrote:

<<Is there an official definition of risk-averse?>>

Hi Wayne

It depends what risk you're talking about.  As we're talking
about
trees,
here's my take on it.

Being risk-averse is a slavish devotion to risk reduction, or
the Sisyphean task of trying to minimise risk.  It's trying to
do either,
no
matter what the level of risk is, how much the risk reduction
costs,
or
what benefits from the risk are lost.  If you conflate a hazard
with
a
risk, you'll be vulnerable to risk-averse thinking.

I thought I'd raised the 'hazard = risk' thing before on here
because
you
keep using 'Tree hazard potential' in your subject headers, and
crowbarring
it into the subject header when you're replying to threads.  But
I
can't
find it in my sent items.  When I read 'Tree hazard potential' I
hear finger nails slowly being drawn down a blackboard.  Here's
why.

A 'hazard' is simply something that could cause harm.

Whereas, 'risk' is the probability of something bad happening.
The probability that the 'hazard' will cause harm.

The problem with Tree Hazard Assessment thinking is that you're
prone
to
look at - What could happen?  There's a hazard.  We need to do
something
about it, or eliminate it.  It's a ‘risk-averse’ mind-set  It'll
also
set
you up for 'hindsight bias' in the event of a tree failure.
Tree
Hazards
can be acceptable (very low) risks.

On the other hand, Tree Risk-Benefit Assessment thinking – What
is
most
likely to happen?  There's a hazard, what's the risk from the
hazard
and
is
that risk acceptable?  What benefits does the hazard provide?
Is
reducing
the risk from the hazard 'proportionate'?  It's a ‘risk-aware’
mind-set.

Cheers

Acer ventura




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