[Talk-GB] Kent Heritage Trees Project - launch event report

[SK53 on OSM]

On 14/05/2011 18:28, TimSC wrote:
> On 14/05/11 17:39, Andy Mabbett wrote:
>>
>> The Woodland Trust do something similar (no URL, sorry, as I'm mobile).
>>
>>
> Do you mean http://www.woodlandtrust.org.uk/en/visit-woods/ ? I 
> already asked for their data set but they were not very 
> communicative... It would be cool to have though. (A fairly 
> comprehensive list of public and permissive access woods for the UK 
> and their operator.)
>
> TimSC
>
>
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I'm sure Andy means this 
http://www.ancient-tree-hunt.org.uk/discoveries/interactivemap/ which I 
think is backed by the Woodland Trust.

My own experience & discussions with local tree experts suggest that the 
data collected by this survey is fairly unreliable. There are too many 
'citizen science' programmes of this kind which don't produce really 
useful data because they lack any quality thresholds. It's best to see 
them as designed to get people involved: essentially they are marketing 
exercises. I've got a blog entry on the stocks about a similar issue: 
I'll probably end up doing several.

To put a bit of context on the 10,000 trees in the Kent programme: the 
Girona tree import was 28,000 trees and I think Tom Chance's Lambeth set 
is of a similar size. The figure I have at the back of my mind for 
Nottingham street trees is 8000, but I suspect that this is too low. I 
know that Nottingham University Campus & the adjacent Wollaton Park have 
over 3000 significant trees (probably excluding ones in woodland): these 
are in our local tree expert's patch. With his guidance the council have 
produced some excellent leaflets on trees in local parks, such as The 
Arboretum <http://www.nottinghamcity.gov.uk/index.aspx?articleid=3383>. 
I presume the BCTV Kent project is therefore restricted to large trees: 
one of the problems with the Ancient Trees survey is that it has tended 
to be affected by wild overestimates of trees size and age. Another is 
that prominent and fast growing trees (think Poplars, which are 
short-lived) tend to be over-represented

I've got a limited experience of a systematic tree survey: I attempted 
to locate all the Oaks in Attenborough Nature Reserve, mapped them 
<http://www.flickr.com/photos/sk53_osm/5492103506> with GPS & measured 
BHG (Breast Height Girth). In an area of around 250 ha this took me 5 
1.5 hour visits for around 100 trees from small saplings to ones upto 3 
m BHG. I did this for the following reasons: a) because the ability to 
say I found insect x on tree y was useful; b) to see how much work was 
required; c) oaks are relatively rare at Attenborough so it was an 
achievable set of data to collect. The data set is now very out-of-date: 
I have not resurveyed to see which trees have survived the new flood 
defense work (most by the railway line will have gone for good), and I'm 
continually noticing trees I missed.

Tree identification is often non-trivial: a professional botantist I 
know was hired to re-survey the Brithdir Arboretum within Coed-y-Brenin 
because the orginal planting plan had either not survived, or which 
trees had survived was not known. He told me that identifying some 
individual trees took him hours. Certain heritage trees have been 
surveyed on a national level for decades: notably ancient Yews, and the 
native Black Poplar 
<http://sppaccounts.bsbi.org.uk/content/populus-nigra-1> (/Populus nigra 
betulifolia/). In the latter case a book 
<http://www.amazon.co.uk/Black-Poplar-Ecology-History-Conservation/dp/1905119054> 
was published by the Botanical Society's Black Poplar referee Fiona 
Cooper. However, the map was selective as landlords have been known to 
fell trees to prevent visits by Poplar geeks. Many counties include 
native Black Poplar in their BAP (Biodiversity Action Plans). Richard 
Mabey has good accounts of both these trees in /Flora Britannica/.

So to summarise: its important to have a clear objective before mapping 
trees. So far on OSM most mapping of trees has been casual, and 
therefore implicitly is for the renderer. I can think of several areas 
where clear objectives can be formulated:

    * In many urban contexts - parkland, amenity grassland, churchyards
      - mapping isolated trees or groups of trees seems both achievable
      and potentially useful.
    * Tom Chance (and others) are interested in locating fruit trees:
      again achievable.
    * I'm probably more interested in rare or unusual trees which are
      usually specimen trees in parks and larger gardens, and I'm keen
      that they be accurately identified. Having a known location of a
      given tree means that one can visit that tree and familiarise
      oneself with its appearance. It's then a lot easier to spot other
      specimens.This, though, is really a complete activity in itself.

A reasonably accurate identification is what really adds value, and 
that's the hard bit.

Jerry


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