UKTC Archive

Re: Tree canopy cover as a sustainability metric: Planning for the future - consultation

Subject: Re: Tree canopy cover as a sustainability metric: Planning for the future - consultation
From: Brynley Andrews
Date: Sep 28 2020 09:23:55
Hi Bill

Thanks very much for your input. It helps me get my head around
perspectives.

How I see it - The TCC on a small site - say an urban park of 1 hectare
could be measured using Google earth and/or CAD survey info every year in
about 1 hour. This data would be a guide as to year to year performance and
fed back into the planning system as an indicator of overall environmental
performance. Lots of parks, lots of data - heah presto we know how our area
is doing.

A ward area could re-do the FR canopy project to the same level of
accuracy/error every year? or 3-5 years and again be a guiding indicator.
Developments that have 'gain' should increase TCC.

A plantation of sitka has wide gaps and until it gets to about 10 years
would mostly not register as TCC using the FR imagery info, which BTW is up
to date within maybe 6 months.

I agree the canopy cover system does not differentiate well between a
wellingtonia and a weeping willow - but this is when site derived data is
used and is more of an ecosystem services measurement than what I am
getting at - which is sustainability metrics.

We live in the societal age of data assimilation and analysis, but arguably
the arb industry and urban tree management has not yet caught up. I am
confident it will. I fully expect that in 20 years drones will be able
survey tonnes of arb data and produce astounding feed back. Arbs need to
get with it and use it to our and societies advantage. Sorry getting a bit
evangelical/ranty here.

Thanks

Bryn





On Mon, 28 Sep 2020 at 09:44, Bill Anderson <anderson.arb.original@xxxxxx.com>
wrote:

Perhaps your average urban-based arb understands that his day-to-day
employment is likely to mean the figures obtained for canopy cover can very
rapidly become inaccurate. And I suspect that counting trees is often
confused with measuring canopy cover as well. Not to mention the conundrum
that a spreading weeping Willow might be only 10 metres tall but have a
crown projection greater than a 30 metre tall Wellingtonia. It might be
better, in terms of particle interception at least, to attempt to work out
total crown volume per hectare. I mean, a recently planted parcel of Sitka
Spruce would bear no resemblance to a similar sized parcel immediately
prior to harvesting, but still provide more or less the same "canopy
cover."
Wouldn't it?

On Mon, 28 Sep 2020 at 09:27, Brynley Andrews <brynley.andrews@xxxxxx.com>
wrote:

Hi Jon

Thanks for the questions. I wish I had the time to answer your questions
thoroughly, & besides this thread is really looking for info to backup
the
principle of using TCC as a metric of sustainability - because of the
arboricultural implications and ease of use/transparency - so as to raise
the issue of tree cover within the planning for the future consultation
process.

1. The <2% I meant is the threshold set by forestry research (FR) for
standard deviation within their UK ward tree canopy mapping project. As a
baseline for further consideration within the planning process. FR give
info linked here - that indicates the UK has an average of 15.8% TCC,
which
based on the hundreds of wards done seems like it is fairly accurate.
https://www.forestresearch.gov.uk/research/i-tree-eco/urbancanopycover/

2. The above FR TCC process is repeatable/reproducible and
transparent/open
access, and so for the sake of a baseline scoping metric of
sustainability measurement I suggest it is good. And simply reflects
common-sense; also, it is readily understandable by all and Google Earth
/
site visits enables verification.

3. As you know, CAD shapes can be derived from drawn/produced polygons of
any shape, from multiple survey methods thereby giving good enough
accuracy
again. I did not envisage circles.

What concerns me more than the technical issues you raise, is that there
is
seemingly a lack of engagement with urban TCC measurement by the arbs. I
hope I am wrong? But that is a whole other topic for another day,
perhaps.

Thanks

Brynley


On Fri, 25 Sep 2020 at 17:58, Jon Heuch <jh@xxxxxxxx.co.uk> wrote:

Brynley



i)                    You can’t measure accuracy! (that is - from
sampling).

ii)                   Please provide me with a reference that suggests
they
are estimating something to “2%”.  If they do have a measure it will be
of
precision. Something very different to accuracy. If you apply more
sample
points your precision increases & that appears to give you a good
measure.
But it doesn’t because of the problems I describe.

iii)                 CAD will very accurately measure what you put into
CAD.
That is not the problem. If you draw a circle around a tree, CAD will
do
a
wonderful job of telling you the area of the circle. The first big
problem
is that images have shadows, varying from image to image; if you are
dealing
with only one image, there will at least be some uniformity across the
image. The second is that trees are not uniform cylinders, spheres or
other
shapes so whatever you measure, however you measure.



You might want to read the musings of Francisco J. Escobedo (used to
work
with I Tree; Google Scholar gives you an entrée to his work) who gave a
talk
at the AA conference in 2016. He at least started to discuss some of
the
statistical issues related to inventory of the urban forest. I can tell
you
simply you won’t pick up modest but real changes in canopy cover!
Undoubtedly you will generate numbers. Undoubtedly they will be
different.
Will they be meaningful? Most unlikely.



Jon






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--
Brynley M M Andrews MSc., C.Env., M.Arbor.A.
www.brynleyandrewsassociates.com
01935 XXXXXX
07970 XXXXXX



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The UK Tree Care mailing list
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The UKTC forum is supported by Bosky Trees arboricultural consultancy and
Stockholm Tree Pits
https://www.stockholmtreepits.co.uk




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

The UKTC forum is supported by Bosky Trees arboricultural consultancy and
Stockholm Tree Pits
https://www.stockholmtreepits.co.uk



-- 
Brynley M M Andrews MSc., C.Env., M.Arbor.A.
www.brynleyandrewsassociates.com
01935 XXXXXX
07970 XXXXXX



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

The UKTC forum is supported by Bosky Trees arboricultural consultancy and
Stockholm Tree Pits
https://www.stockholmtreepits.co.uk