Mapping natural and planted habitats

Posted by BushmanK on 19 August 2015 in English (English)

OpenStreetMap has many tags, inherited from a natural language with blurred meaning and definitions, depending on each mapper's understanding of associated natural language term. Also, many tags are representing more than one property of an object, such as, say, type of flora, populating particular area and presence of management of this area. (Good example is natural=grassland and landuse=grass.)

In an ideal case, any classification system should have only "atomic" properties instead of "molecular", where several real properties are linked. (Good example is the recently introduced scheme with leaf_type= and leaf_cycle= - independent properties instead of linked ones.)

One of the extremely widespread tags with both bad features is natural=wood.

It belongs to natural=* class, and it gives people an idea, that only natural habitats should be tagged with it. Therefore, we also have landuse=forest, which means the same kind of habitat, but more related to man-made objects.

Actually, it creates the really huge problem. First, let's try to explain what exactly we should map with it.

Both natural wood and any kind of planted forest are areas of vegetation, dominated by trees. But there is no clear definition (in OSM), what does "dominated" mean.

natural=wood should, supposedly, tells us, that area of vegetation forms "natural habitat". But there is no clear explanation, what does "natural" mean.

landuse=forest should, supposedly, tell us, that area of vegetation is managed, or planted, or forms artificial habitat, or trees there are non-native. There is no clear explanation, is there any difference between landuse=forest and landuse=plant_nursery - difference is only implied, because nursery should be only used to plant young trees for sale or for planting it somewhere else for forestry management purpose.

So many variants, so many assumptions and lots of guessing.

Currently, in British OSM community, there is a process of habitat=* tagging scheme discussion going on. Concepts and definitions there are mainly based on Joint Nature Conservation Committee works and publications, including Handbook for Phase 1 Habitat Survey. I like this approach, but there is a problem: ecologists usually have different goals for their projects than OSM community has. They can use plain (single dimension) classifications with all existing variants, represented by compound classes.

This approach has positive features: it's impossible to classify any object with non-existent set of properties, and it's also impossible to classify anything incompletely, because each class has full set of required properties and its values. But in OSM it doesn't make any sense: mappers are non-professionals, and often they can't evaluate all required features to use compound classes. That's why multi-dimensional classification with no mandatory properties makes much more sense in OSM.

Multi-dimensional classification means that you can have any set of independently determined properties. For example, tagging scheme can have color= and material= properties. It means, we can tag only color, only material or both. We also can add third property (say, shape) to scheme completely independently. Single-dimension scheme will require total revision in this case, because adding another property will require making completely new classes.

Like, originally we had classes: "red_steel", "green_steel", "red_wood", "green_wood", Adding shape to single dimension classification will make it look like: "red_steel_round", "green_steel_round", "red_wood_round", "green_wood_round", "red_steel_square", "green_steel_square", "red_wood_square", "green_wood_square".

Looks extensive, right? So, multi-dimensional classification with independent properties is definitely more suitable for OSM. Then, lets try to establish basic properties for different types of tree vegetation, that will allow us to map almost everything we want without implications and assumptions.

First, we need fundamental tag to show, that "here are trees". Trees in general, nothing more. I believe, that natural=wood can probably work for it. Its meaning is currently blurred enough to use it like very broad thing.

What to map with this tag? Answer is simple: any area, where trees grow, regardless of anything. Yes, if trees are sparse enough to see them independently, you can try mapping them as independent trees with natural=tree. But even if you can, it doesn't mean you have to.

Ecologists and forestry management using canopy coverage as a criterion for classifying any area as "forest". But I think, for our purposes we can have certain scale of percentage ranges, for example:

  • 0..25% of coverage - single trees, not recommended to tag as wood, recommended to tag single trees
  • 25..50% of coverage - sparse wood
  • 50..100% of coverage - wood

These values (single, sparse, normal) can be assigned to density key.

It's pretty easy to use these ranges, because if canopies covering a bit less than a half of territory, it's sparse, if more - normal wood.

Origin of wooded vegetation area can be tagged (if we know it), and it's pretty obvious, which values to use for this property:

  • natural
  • planted
  • mixed

But it only a kind of historical reference information, because 100 years old plantation of native trees is currently unlikely looks differently from completely natural forest, even in aspect of rows.

Therefore, we need something for current habitat state. It's only about how it looks and how similar is it to reference natural habitat. Based on ecological classifications and practical experience, we can define values for this key as:

  • natural (which means similar to natural)
  • semi-natural (which means, this area has significant traces of planting, cleanup, removal of dead branches, or, otherwise, being artificially planted, it has traces of succession, growth of new young trees and scrub)
  • artificial (which means, it looks completely or almost completely different from natural habitat typical for this area).

These definitions are just a framework, but it explains the idea.

Management is another obvious property, describing the situation, but it could be tricky to find right values for this key, because management can consist of very different works. Therefore, I suggest using general tag like managed=yes in case if it's managed and making separate scheme (considering namespace usage) for types of management, such as cleanup, fire protection, pest control and so on.

Obviously, these framework keys and values are only an example, because correct tagging scheme should be discussed and tested on different real cases. Also, definitions for values should be given in clear manner to avoid any contradictions, broadening of usage and so on. But as a framework, it gives good example of classification, based on independent "atomic" properties.

For sure, it doesn't solve certain problems completely. Like, it doesn't help to filter out tree groups within city limit (which should be done using spatial functions of SQL extensions). But it is potentially able to solve all controversy of real situations, like proper and simple description of difference between city park vegetation and wild forest vegetation.

Comment from Warin61 on 19 August 2015 at 09:00

Quibble: British English ... colour not color. :)

landuse=forest to me means there will be wood harvesting from this area.

nature=wood ... means the area has plants of such a size that wood is present. There is an area in Australia called the Nullabor .. meaning no trees. You can find wood there for a camp fire but there are no large trees. So I'd still mark it natural=wood. nature=wood means there may not be wood harvesting in the area.

Origin of wooded vegetation ... err no. Your thinking or the way it was planted rather that if it is native to the area, native to the country or non native. And I'd make the tag broader without loosing the essential information For example; planting=natural, manual, automated ... I am certain there are many varieties of the planting method. by seed, tube stock, pot ... for example.

Origin of vegetation could be taken as native (to the area, to the country) or non native. Oh and there are the cloned, hybrid, grafted... if you want to go that far. Again this could be applied to things like orchards .. not just forests/woods.

Managed... National Parks are managed .. and some of it is natural=wood. But the management is quite different from a tree plantation used for wood production.

Comment from BushmanK on 19 August 2015 at 17:56

Warin61, I got used to US English, so, "color", "neighbor" and so on. Sorry, it's officially a bit different language.

Your examples are another proof of fact, that natural=wood is understood and used in own way by every mapper. My point is, we need to bring this blurred meaning to the "least common divider" and remove any controversy. Example of successful introduction of leaf_type and leaf_cycle gives me an idea, that it is possible to get rid of unclear meaning of this tag.

Origin and management are only examples of "atomic" properties in this hypothetical scheme.

And, as I said, management property could be binary (yes/no) or amended by completely separate scheme, describing management.

My point in case of habitat state is based on British JNCC handbook - you can find something useful for understanding this concept there.

Comment from Warin61 on 18 December 2015 at 23:19

One further development...

The problem arises from the fact that in general the mapper cannot tell what the 'forest' is used for and if it is 'natural'.

That problem goes away if the tag landcover=forest is used. It just says there is a forest there. And that is what most data users take the other tags to mean due to the present confusion.

When and only when it is know what use is made of it, and/or if it is 'natural' then those tags could be used.

Comment from BushmanK on 18 December 2015 at 23:45

If we really want to keep keys and values human-readable and a kind of intuitively understandable, it's probably better to avoid usage of "forest".

Word "trees" is more general term. Forest is an ecosystem. While group of trees could be a part of ecosystem, planted park, nursery or anything else. Then, known properties could be added.

Comment from SK53 on 9 January 2017 at 14:32

Dont know why I didn't comment before. I think I am very much in agreement with this. It's not just that using a multiple dimensional tagging approach helps inexperienced users, but in many cases even the most experienced user only knows "here be trees".

Other dimensions:

  • Canopy height
  • Species mix
  • Ground layer: is this a bluebell wood or a marsh
  • Field layer: is it bracken, heather, bilberry, bruchholz, brash, bramble
  • Shrub layer: does it exist, what is it composed of, density etc
  • Tree spacing
  • Dominant species (when appropriate)
  • in management: plantation (i.e. regularly spaced in rows for easier harvesting), coppicing with standards, selective removal etc

Comment from BushmanK on 9 January 2017 at 16:43


Experience (time since the first edit and number of edits) have very little effect on quality if a person doesn't want to learn. But I don't see anything bad in the most basic tagging like "here be trees" - when it is done properly, it's completely acceptable.

Comment from SK53 on 9 January 2017 at 17:00

Again can only agree. There's many a time when it's the only thing I've been able to do because image resolution not enough to pick out which parts of a woodland are conifers & which not.

Comment from BushmanK on 10 January 2017 at 02:31


Exactly. Good tagging scheme should not force mapper to make any assumptions about things he doesn't know. Any details should always be strictly optional.

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