UKTC Archive

Re: CAVAT .....not really....climate change, peer review, bristlecones, hockey sticks, PCA......

Subject: Re: CAVAT .....not really....climate change, peer review, bristlecones, hockey sticks, PCA......
From: Scott Cullen
Date: Dec 21 2010 21:43:03

  ----- Original Message ----- 
  From: Rupert Baker 
  To: UK Tree Care 
  Sent: Tuesday, December 21, 2010 4:11 PM
  Subject: RE: CAVAT .....not really....climate change, peer review, 
bristlecones, hockey sticks, PCA......


  If you want to have a look at Prof Jim's article, here is the link:

  http://www.springerlink.com/content/l03207w075150645/fulltext.pdf

  and the reference:
  Journal of Environmental Monitoring & Assessment: Vol 116; No's 1-3,
  PPs 58-80

  SC Ha!  No wonder I couldn't recall which journal.  Thanks for the ref.

  The bit that interested me was:  on average, the method gave values 66 times
  higher than the CTLA method........... largely because of property values in
  Hong Kong - I'd never be able to afford to live there!

  SC  As I recall there were some issues with the use of CTLA methods and his 
"CTLA" values were lower than might properly result.  But none the less, even 
corrected, the multiple from CTLA to FEM would be several times.  Also as I 
recall, the relulating FEM values were not necessarily based on market data 
(actual contributions of trees to property market values) but rather the 
inputs and adjustments were intended to result in values high enough that 
trees were not trivialised in comparison to property values.  No I suppose I 
should test my recollections by re-reading the paper.
  SC You and I could not afford to live in posh neighborhoods, but I imagine 
there are neighborhoods where we could pool our money and afford a closet.

  Cheers

  Scott


  Rupert

  -----Original Message-----
  From: Scott Cullen [mailto:dscottcul@xxxx.net] 
  Sent: 21 December 2010 18:16
  To: UK Tree Care
  Subject: Re: CAVAT .....not really....climate change, peer review,
  bristlecones, hockey sticks, PCA......


    ----- Original Message ----- 
    From: Jon Heuch 
    To: UK Tree Care 
    Sent: Tuesday, December 21, 2010 12:00 PM
    Subject: RE: CAVAT .....not really....climate change, peer review,
  bristlecones, hockey sticks, PCA......


    Peer review may have its flaws, but it does help an editor weed out
  problem papers - just that,
    help, not guarantee. However, just because it may have flaws shouldn't put
  you off it. On the other
    hand, having CAVAT "peer" reviewed by arborists would have its limitations
  - it needs to be reviewed
    by a wider group of professionals.

    SC Accepting the flaws, the question would be "peer review for what?"  The
  peer review process is most applicable to research.  Was the experimental
  design acceptaable?  Were the data and analyses appropriate.  Were the
  properly arcane and symbol heavy statistical tests applied?  And so on.
  "Peers" are folks with some familiarity with the basics of research and
  statistics and the topic area.

    SC would CAVAT's peers be the LTOA?  Well this is keen, it does what we
  want and it can be learnt in a day.  Economists would not get it because it
  is not what normative economics tells them the world should be like.
  Chartered surveyors sort of get it and are bothered by the results not being
  tied to "market."  Nevermind that amenity trees, especially street and park
  trees, are not market goods... they should be.  CAVAT could be reviewed for
  its maths, that is the calculations. One of the biggest questions is the
  validity of the population density multiplier (or whatever it is called).
  Understand that the adjustment assumes that a tree in central London MUST be
  worth more than a tree in a country churchyard because more folks enjoy its
  benefits.  Intuitively appealing.  How is the resulting number tested?  When
  we undertstand the mnethod was crafted to create eye catching numbers then
  it is what i claims to be.

    SC C.Y. Jim who is a professor in Hong Kong and fairly prolific in
  publishing developed a Formulaic Expert Method to Value Trees in a Compact
  City.  It was peer reviewed and published (not sure in in Arb Jour, Urban
  Forestry and Urban Greening, Journal of Arboriculture or Landscape and
  Regional Planning).  FEM's stated purpose was to arrive at figure
  sufficiently large to discourage tree loss in development in Hong Kong.
  Would CAVAT fair any differently in peer review?

    SC IMO part of the problem is that few - even in the various "peer"
  communities - really understand the range of meaning for "value."
  Economists want it to be one thing, surveyors another and perhaps arbs
  another.  And there is nothing essentially wrong with that.  The problem is
  when one concept is tested by the preconceptions of another.  Valuation is
  always an answer to a question or an aid to a decision.  A valuation method
  can only be judged by how well it addresses the question or the decision.
  And the decison maker might be aided by any number of questions, that is
  look through various lenses.

    Scott Cullen


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The UKTC is supported by The Arbor Centre
http://www.arborcentre.co.uk/