UKTC Archive

Re: RE: Statistical Risk vs Ecosystem Services - does this compute?

Subject: Re: RE: Statistical Risk vs Ecosystem Services - does this compute?
From: Julian Morris
Date: Dec 06 2019 13:07:24
Thanks, that's useful. I see it is indicating monetary value as willingness 
to pay or willingness to accept compensation, which is a parallel universe to 
commonly used tree valauation bases (except to the extent that depreciated 
replaceent costs are tentatively based on current willigness to pay).

I might have to write to Santa for the full versions.

Julian A. Morris - Professional Tree Services
jamtrees.co.uk  and  highhedgesscotland.com
0778 XXX XXXX - 0141 XXX XXXX


Sent: Friday, December 06, 2019 at 12:42 PM
From: "Tim Moya" <tim.moya@xxxxxxxxxxxxxxxx.co.uk>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: RE: Statistical Risk vs Ecosystem Services - does this compute?

You can get a cut down version here if it's ISO 14008 you're after
https://www.iso.org/obp/ui/#iso:std:iso:14008:ed-1:v1:en 

Tim Moya 
-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
<uktc-request@xxxxxx.tree-care.info> On Behalf Of Julian Morris
Sent: 06 December 2019 12:05
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: Statistical Risk vs Ecosystem Services - does this compute?

As one side of the equation it seems very relevant. Oh to have free access 
to these documents long enough just to size them up. I am hesitant to spend 
£90 on something that might not be that useful. But if anyone's read it and 
thinks it's a powerful tool, I might.

Julian A. Morris - Professional Tree Services jamtrees.co.uk  and  
highhedgesscotland.com
0778 XXX XXXX - 0141 XXX XXXX


Sent: Thursday, December 05, 2019 at 10:50 PM
From: "Michael Richardson" <richardsontreecare@xxxxxx.com>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: Re: Statistical Risk vs Ecosystem Services - does this compute?

A slight bit off the topic of statistics but perhaps useful.

The ISO standard for
CALCULATING THE VALUE OF THE ENVIRONMENT


https://www.iso.org/news/ref2456.html?utm_medium=email&utm_campaign=IS
O%20Newsletter%20December%202019&utm_content=ISO%20Newsletter%20Decemb
er%202019+CID_d9aba02efcaf0cafa01c49efc3f27fe9&utm_source=Email%20mark
eting%20software&utm_term=Read%20more



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 Thu, Dec 5, 2019 at 1:58 PM Rod Leslie <uktc@xxxxxx.tree-care.info> 
wrote:

Quite right. There is no way a proportion of unpredicted failures is 
the same as random - there's no question that inspections can 
identify many of the factors - and likelihood - involved in failure, 
but we know, not all of them. We can even predict some unpredictable 
failures - for example, the shedding of branches by big old Beech - 
as far as I know, noone can accurately predict thyat a particular 
limb is going to be shed in a particular timeframe  - but we know 
for certain there is a particular and recurrent risk - so just don't 
park the BMW under your big old Beech in a hot summer.


Rod Leslie

On 05/12/2019 18:11, Bill Anderson wrote:
No one will read this...?
You're wrong Julian, I've just read it, twice, and I see what you 
mean. I think....
Bill.

On Thu, 5 Dec 2019 at 17:43, Julian Morris <jamorris@xxxxx.com> wrote:

No-one will read this, but for the record....

If we are to rely on the science (or possibly more correctly the
mathematics) of statistics, we must speak the language with 
consistent meaning. We shouldn’t mix the lay and the mathematical 
meaning of
words. So
I have reached for a couple of text books I have in the office. 
They clarify that ‘random’ means equally likely to occur. In the 
context of
tree
failure and the hypothesis that tree failures are random, this 
would be
to
say that, regardless of size, position, condition, species, soil etc.
every
and any tree is as likely to fail as the next.

We all know that we don’t have a perfect database of tree 
failures (and
of
course tree non-failures) but I think it self-evident that the
hypothesis
is not true. I am confident this would be backed up by a 
questionnaire
of a
huge number of people that have a working knowledge, or better, 
of
trees.
But the matter of statistical significance has been raised, and 
merits consideration. Statistical significance is a measure of 
the likelihood
that
a relationship between two or more variables is caused by 
something
other
than chance. ‘Chance’ is of course synonymous with ‘randomness’ 
in this context. An important part of the concept of statistical 
significance is that it is not a black-or-white matter. 
Significance must always be
stated
and calculated with reference to a ‘confidence level’, which is
quantified
(indirectly but nevertheless based on) the deviation between 
sample
results
and a known normal distribution of outcomes. Large sample sizes 
can help significance levels, but it’s only as a matter of degree.

What statistics and a hypothesis hopes to achieve is 
demonstration that there is a statistically significant (to a 
persuasive confidence level) correlation between two variables. 
This in turn can support (but not
prove)
a causative link.

So say one postulates that Meripilus causes failure of  mature 
beech at the base. And we might use this as a specific theory 
that, if not
refuted,
debunks the theory that all tree failures of all species are 
random. So
we
might use statistics to record and show that in a group of mature 
beech, some of which have outward signs of Meripilus infection 
and some of
which
don’t, over a fixed period of study nearly all that have 
Meripilus
failed
and nearly all that didn’t, didn’t fail. We thus have a normal
distribution
from the non-infected trees and can show to some confidence level 
that
the
infected trees deviate substantially in failure rates from the 
normal distribution.  We thus have correlation between infection 
and failure, a significant absence of ‘random’. Now, one could 
deny that there is a causative link, but that’s a different 
problem…

One has to be very careful with the terminology. A lack of 
statistical data to make up normal distributions and a lack of 
data for a tested hypothesis might mean that there is currently 
no statistically
significant
evidence, but that’s all it means, it doesn’t mean that failure 
is
random.
Absence of data does not mean absence of potential to demonstrate 
correlation and in statistical terms does not mean random.

Stepping out of the specialist realm of statistics, I’d say 
there’s a reason why no-one has statistically analysed the 
correlation between Meripius and failure, and that’s because it’s 
self-evident. Search all
the
authoritative text on the subject of the modus operandi of 
Meripilus,
and
you won’t find any that have samples, statistics, confidence 
levels and statistical significances. They all just say Meripilus 
caused failure.
And
I’ll warrant none say that the absence of Meripilus causes failure.

Conclusion? Absence of statistical evidence does not mean random.
Inability to separate out one variable from many to show a 
correlation
with
another variable does not mean an absence of causation. Only 
statistical evidence that shows no correlation means random.
And stepping even further back from statistics, any book and any 
witness will tell any judge that Meripulus causes failure and 
that if you spot
it
you need to have very good reasons not to foresee it causing harm 
or damage, because otherwise you will be found negligent for not 
acting (on seeing it) by reducing or eliminating the risk. In 
that sense, this is
why
our profession is important and useful, and why statistics plays 
at
best a
supporting role. The law imposes a duty of care, and the 
non-randomness
of
tree failure IS the line that we call ‘reasonably foreeable’.

I have a well-thumbed copy of ‘Statistics’ by F Owen and R Jones 
here, which I bought second-hand a couple of decades ago, and I 
have just
noticed
that the previous owner has written in block capitals inside the 
back
cover
“HELP I AM TRAPPED INSIDE A HUMAN BODY”.  It somehow seems 
apposite. The law only requires us to be human, no more and no less.


Julian A. Morris - Professional Tree Services jamtrees.co.uk  and  
highhedgesscotland.com
0778 XXX XXXX - 0141 XXX XXXX


Sent: Thursday, December 05, 2019 at 12:51 PM
From: "Jim Quaife" <jq@xxxxxxxxxxxxxxxxx.co.uk>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: RE: RE: Statistical Risk vs Ecosystem Services - does 
this
compute?
That tree failures are random is a factor in the science of 
statistics,
but in our terms it is merely that we cannot accurately predict 
them,
nor
do we have any idea how effective our surveys are in any 
quantifiable
sense.
This does not mean that we shouldn't survey trees, because 
intuitively
it is beneficial (isn't it?).  For one thing, without tree 
surveys
insurers
would walk away.
We see things that we regard as requiring action and there is no 
doubt
that in so doing we simply must have prevented some incidents.  
But we
have
no precise idea with anything other than a general feeling that we 
have.
Being aware of this does not discredit our profession (it is 
more than
a
'trade'), in fact quite the opposite - in fact (without citing
Rumsfeld!)
that we are aware that we don't know something is often as 
important as knowing something.
The difficulty is that in this day and age there is increasingly 
no
such
thing as an "accident" inasmuch as there is always a search for 
someone
to
blame.
All we can do is to use our knowledge and experience as best we 
can,
and
that qualifies as being conscientious and professional.  I don't 
see a conflict - the alternative is naivety.
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info [mailto:
uktc-request@xxxxxx.tree-care.info] On Behalf Of Rupert Baker
Sent: 05 December 2019 11:44
To: UK Tree Care
Subject: RE: RE: Statistical Risk vs Ecosystem Services - does 
this
compute?
Agreed, Michael- and even that can be influenced by its 
environment - 1
atom of U235 by itself - decays randomly.... 1 atom in a block of 
U235
of
say 2.5Kg upwards - does not decay randomly, but in concert with 
its fellows....
To argue that tree failures are random does our trade no 
favours; it is
possible to assign probabilities of failure to trees with a 
degree of accuracy; even if no-one can say exactly when a 
specific tree or part
may
fail; we can be fairly sure (to take a reductio ad absurdum) that 
a
5-year
old seedling is unlikely to blow over, whereas a large mature 
beech with half its root system cut off during a housing 
development, say 5 years before; and evidence of extensive 
activity of decay fungi as a result, probably wont survive a good 
blow from an unsuitable direction.....
Mind you, even if wind events are not random, they are still not
accurately predictable; and in UK at least, it is the interaction
between
wind and trees that causes most failures.
Atb
Rupert

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info On Behalf Of Michael
Richardson
Sent: 04 December 2019 13:14
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: RE: Statistical Risk vs Ecosystem Services - does 
this
compute?
I believe that only truly random event in nature is the decay of 
a
radionucleotide atom.

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, Dec 4, 2019 at 7:53 AM Jim Quaife 
<jq@xxxxxxxxxxxxxxxxx.co.uk>
wrote:
We just have to disagree Julian.
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info [mailto:
uktc-request@xxxxxx.tree-care.info] On Behalf Of Julian Morris
Sent: 04 December 2019 12:43
To: UK Tree Care
Subject: Re: RE: Statistical Risk vs Ecosystem Services - does 
this compute?

Jim, this havse come up before and I explained at length why I 
disagreed with your suggestion that tree failures are random. I 
still disagree with you. The timing of individual failures can 
be a result of complex things and may not always be 
foreseeable, but it's not random. The whole idea of tree risk 
assessment is that the law expects a reasonable person to act 
on foreseeable harm or damage, and so people like us are 
employed to assess trees to see if all the complex things come 
together and amount to 'foreseeable'. In those cases the 
failure is demonstrably not random, and since it's part of a 
continuum with an arbitrary acceptable/unacceptable line marked 
on it, no
unforeseeable tree falures are random either.
I'd give you "The problem with tree incidents is that they are 
complex, such that objective quantification and prediction is 
often so imprecise that they appear random."


Julian A. Morris - Professional Tree Services jamtrees.co.uk  
and highhedgesscotland.com
0778 XXX XXXX - 0141 XXX XXXX


Sent: Wednesday, December 04, 2019 at 12:07 PM
From: "Jim Quaife" <jq@xxxxxxxxxxxxxxxxx.co.uk>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: RE: Statistical Risk vs Ecosystem Services - does 
this
compute?
Hi Chris,
The problem with tree risk statistics is that in the science 
of stats
they are not significant - I didn't know this but I have been 
educated by someone who does.
I thought that statistical significance was to do with the 
sample size,
but it is not. Significance is determined by the absence of
randomness.
This is not always possible and so stats which contain 
randomness have to be adjusted to compensate, and that usually 
means that the reliance one can put upon them decreases 
proportionately.
The problem with tree incidents is that they are random.
We like think that our tree surveys are comprehensive and 
professional
(which they are - hopefully) but accurate prediction of tree 
failures is virtually unheard of.  We specify work that 
requires attention where we can anticipate failure, but we have 
absolutely no idea whether in so doing we have actually prevented 
an incident.
Intuitively we think we have of course and I do not question 
the integrity of surveyors (myself included!), but there is no 
way we can
prove it.
Regretfully it follows that any calculations based on a random 
data are
of questionable worth in actuality.   Interesting yes, but 
applicable?
We all love numbers as they provide reassurance (particularly 
to
insurers who hover over all this), but I would be very wary of 
basing any sort of policy or programme on such calculations.
Although it may sound "woolly", tree risk assessments are 
justifiable
because the alternative of not conducting them is not.
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info [mailto:
uktc-request@xxxxxx.tree-care.info] On Behalf Of Corder, Chris
Sent: 04 December 2019 11:43
To: UK Tree Care
Subject: Statistical Risk vs Ecosystem Services - does this 
compute?

Dear all,

I am a sad case. I only have numbers to comfort me.
So I was wondering where the risk-benefit of trees might lie.
Maybe someone has already done this?
If not, does the following compute?

For arguments sake...lets agree that the background of risk of 
death in
'public spaces' in the UK seems to be in the order of 
1/10,000,000
Lets also assume/agree that the Value of Statistical Life is 
£2M
6 deaths per year = value of risk of £12M per year “A value of 
statistical life of £1,000,000 is just another way of saying
that a reduction in risk of death of 1/100,000 per year has a 
value of
£10 per year” (HSE, 1996)"
Therefore, divide £12M by 1/10,000,000 = risk value of £1.20 
The i-Tree Eco London study found that 8,421,000 trees 
provided
£132,700,000 per year of ecosystem services i.e. £15 per tree 
per year (or near as damn it). So lets assume £15 per tree 
might be about
right.
£15 eco value per tree/£1.20 risk value = 12.5 So...is it 
right to say that the background risk from trees would need
to be 12.5 times greater before the ecosystem benefits start to 
become outweighed?
If so, then presumably the background risk from trees could 
increase to
somewhere in the region of 1/800,000 before the risk starts to 
outweigh ecosystem benefits?
(Which is sort of where the Tolerable/Broadly Acceptable 
region of the
ToR Framework lies...is this coincidence?)
Does this compute or have I gone start raving mad?

p.s. I get the daily digest...so I won't see any replies in 
real
time.
So thanks in advance. And sorry in advance for delay in reply.
All the best,
Chris

Christopher Corder PDArb (RFS), BSc (Hons) in arboriculture, 
MArborA Assistant Arboricultural Manager Hampshire Highways
Tel: 0300 XXX XXXX
Web: www.hants.gov.uk/roads
@Hantshighways

© Hampshire County Council 2017 | Disclaimer | Privacy 
Statement

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info <
uktc-request@xxxxxx.tree-care.info> On Behalf Of Alastair Durkin
Sent: 03 December 2019 08:56
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: RE: Replacement trees in an area TPO

Hi Jon the situation is this:

If you have an area TPO and allow a tree to be removed, 
subject to
replacement planting then you MUST either make a new TPO on the 
replacement OR formally 'vary' the TPO to include the new 
individual tree. Otherwise the tree is not protected.
The 'C' business is for giving effect to planning conditions 
under s197,
it's not for TPO app conditions. See section 4 of the model order.
Hope this helps.

Alastair


-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info <
uktc-request@xxxxxx.tree-care.info> On Behalf Of Jon Heuch
Sent: 01 December 2019 14:14
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Replacement trees in an area TPO

Good folk of uktc



Remind me what should happen if the removal of a protected 
tree covered
by an area order is allowed, but a condition is given to plant 
a replacement tree? The order may or may not contain separate 
individual protected trees.


The order can't be altered to include an individual tree shown 
within
the protected area, can it?


The tree officer who gave permission will remember but what is 
there on
record to show a protected replacement tree? The replacement 
tree will clearly be younger than the order, so not seemingly 
protected to subsequent tree officers.


Do area orders get conditional replacement trees? Do they get 
Tree
Replacement Notices?


Is this just a failing of the Area order?



Jon








--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural 
consultancy
http://www.boskytrees.co.uk/


--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural 
consultancy
http://www.boskytrees.co.uk/


--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural 
consultancy http://www.boskytrees.co.uk/



--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural 
consultancy http://www.boskytrees.co.uk/




--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/



--
The UK Tree Care mailing list
To unsubscribe send 
mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy
http://www.boskytrees.co.uk/



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/



--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/




--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/







--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/




--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/





--
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy 
http://www.boskytrees.co.uk/



-- 
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy
http://www.boskytrees.co.uk/





-- 
The UK Tree Care mailing list
To unsubscribe send mailto:uktc-unsubscribe@xxxxxx.tree-care.info

The UKTC is supported by Bosky Trees arboricultural consultancy
http://www.boskytrees.co.uk/