[Tagging] Feature Proposal - RFC - Dehesa

Christoph Hormann osm at imagico.de
Fri Aug 30 09:57:50 UTC 2019

On Friday 30 August 2019, Diego Cruz wrote:
> I have recently proposed a new tag in the Wiki, because none of the
> existing landuse tags seem to match it. A dehesa is a type of land
> that combines a forest with either fields or pasturelands (or both)
> at the same time. It is extensively used in the Iberian Peninsula,
> both in Spain and Portugal. Please see the details in my proposal
> below:
> https://wiki.openstreetmap.org/wiki/Proposed_features/Dehesa

This is certainly a valid idea for inventing a new tag and it is good 
that you open up discussion early.  Let me take this as an example for 
two things that have in the past been decisive on the broader success 
of tags:

* local verifiability.  The primary definition of your tag is for areas 
in a certain region that are in the cultural tradition of that region 
called a certain way.  You try to list a few verifiable criteria what 
not to use the tag for - but these are one sided criteria.  Because 
natural=wood does not rule out use as pasture (and neither does 
landuse=orchard, which is also used for cork oak plantations), 
landuse=farmland does not rule out the presence of trees or the use as 
pasture and many savannas (for which we have no specific tag at the 
moment) are created by human influence.  A good tag is one where a 
local observer, even a casual one like a traveler quickly coming 
through, can without much difficulty determine locally if the tag 
applies or not.

* generic meaning.  As already mentioned you draft this as a region 
specific tag although agroforestry is a practice that exists in many 
different parts of the world in different forms.  Such tag will either 
stay a local speciality tag without much chance for being interpreted 
by global data users and possibly mirrored by other region specific 
tags with similar but slightly different meaning or it will morph into 
a broad umbrella tag - for example for any kind of 'area with trees 
that does not really qualify as wood/forest'.  Well known examples for 
such tags are natural=fell and landuse=village_green.

There are three potential tagging concepts i could imagine could be 
derived from your idea that would seem more promising in that regard:

* a tag for agroforestry landuse.  This of course would only be locally 
verifiable if there is active agricultural use.  That would only 
qualify those dehesas that are actively used for agriculture as such.  
And it would say very little about the physical appearance and 
ecological characteristics of an area.

* establishing a generic tagging concept for secondary characteristics 
of areas - like use of orchards as pasture, underbrush in a forest or 
scattered trees on a meadow.  This could be quite easily implemented 
using natural:secondary=*, landuse:secondary=* etc.  Dehesas would 
under such scheme be something like

- landuse=farmland + landuse:secondary=orchard
- landuse=meadow + landuse:secondary=orchard
- landuse=orchard + landuse:secondary=meadow

* creating one or more region specific secondary tags for exising 
primary tags like landuse=farmland or landuse=orchard for documenting 
the region specific ecological characteristics of the area.

Christoph Hormann

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