Proposal:Wetlands Expansion
| Wetlands Expansion | |
|---|---|
| Proposal status: | Draft (under way) |
| Proposed by: | Osmus, MaggieMaps, jake-low |
| Tagging: | wetland=*, salt=yes, anthropogenic=yes |
| Applies to: | 
|
| Definition: | A set of tags for mapping wetlands |
| Draft started: | 2026-11-06 |
Proposal
OpenStreetMap US is proposing an expansion and modification of the current tagging for wetlands. These changes intend to more accurately reflect the diversity of wetlands and provide more precise details about individual wetlands within the OSM data model. The following tags are intended to be used on wetland areas.
The new tags being proposed are:
wetland:connectivity=*wetland:vegetation=*wetland:landform=*
The following tags are already in use, and this proposal offers expanded definitions in relation to wetlands:
salt=yes/noanthropogenic=yes
Disclaimers
OpenStreetMap US is partnering with the Environmental Policy Innovation Center, who has been granted funds to build OpenWetlandsMap, a comprehensive map and dataset of wetland features built on OSM data and based on their ongoing work in environmental stewardship and policy. The grant period began in December, 2025 and is ongoing. This proposal is informed by discussions with dozens of OpenStreetMap contributors and wetland scientists that have occurred in the process of building OpenWetlandsMap.
The authors of this proposal include Maggie Cawley, Jake Low, Alyssa Castronuovo, and EmmaLi Tsai.
No generative AI was used in the writing of this proposal.
Rationale
The values used in combination with the key wetland=* cover a wide array of different types of wetlands, but are generally broad categorizations that may or may not imply additional information about the wetland itself. For example, the definition of the wetland=fen tag includes an idea of the vegetation present on the wetland (“mosses, grasses, sedges, reeds, and wildflowers”) and where its water comes from (“groundwater-fed”), but does not indicate the geography of the wetland. The definition of wetland=reedbed only includes information about present vegetation (“tall, non-woody plants”), but does not mention what causes the presence of water or how the wetland is connected to the surrounding landscape. When applied to the real world, the current wetland tagging scheme does not accommodate many wetland ecosystems. The Bonneville Salt Flats in Utah are a naturally occurring wetland habitat. Of the three wetland=* values available for saltwater wetlands, wetland=salt_marsh may seem the most appropriate, though its definition states that there should be vegetation present, which is not the case with the Bonneville Salt Flats (currently, the area is tagged as landuse=salt_pond, which is also inaccurate as it implies the area is human-made for the purpose of extracting salt. Considering there are various ways to classify wetlands, these broad categorizations ultimately limit OpenStreetMap’s ability to represent the variety and nuance of wetlands.
The proposed tags are intended to compliment the existing wetland=* values and provide additional, objective data regarding the base components of a wetland (such as its source of water, the primary vegetation present, and its relation to the surrounding landscape). This data is valuable to all persons referencing OpenStreetMap to help determine wetland function and its importance to the surrounding ecosystem. For example, agencies stewarding wetlands would find information regarding the wetland’s potential for providing habitat for migrating shorebirds by using the proposed wetland:vegetation tag and the observable values of forested, shrub, emergent, submerged, floating and no, instead of or in addition to the definition of the wetland=* tag applied.
Providing additional tags that indicate the base ingredients of a wetland (soil, vegetation, and hydrology) would also allow OpenStreetMap’s wetland data to be applicable internationally, by mappers with different regional definitions, and by environmental scientists utilizing varied standards and classification systems across the world.
Tagging
New key wetland:connectivity=* to indicate the primary source of water for the wetland. This tag would be applied to the areas tagged as natural=wetland.
| Key | Value | Comment |
|---|---|---|
wetland:connectivity
|
river
|
The wetland is connected to a river, and the river is the primary water source for the wetland |
lake
|
The wetland is connected to a lake, and the lake is the primary water source for the wetland | |
ocean
|
The wetland is connected to the ocean, and the ocean is the primary water source for the wetland. Water levels on the wetland may be influenced by ocean tides. | |
isolated
|
The wetland is geographically isolated, and primarily receives water from precipitation or groundwater |
New key wetland:vegetation to denote the type of vegetation present in the wetland. This tag would be applied to the areas tagged as natural=wetland.
| Key | Value | Comment |
|---|---|---|
wetland:vegetation
|
forested
|
The landscape is primarily covered by tall, woody vegetation creating an overhead canopy. |
shrub
|
The landscape is primarily covered by woody shrubs, bushes, and/or low trees with branches. | |
emergent
|
The landscape is primarily covered with rooted plants with stems and leaves that grow above the surface. These plants are soft-stemmed, and branches are not present. | |
submerged
|
The landscape is primarily covered by aquatic vegetation that is completely submerged in water | |
floating
|
The landscape is primarily covered by vegetation floating on the surface of the water (example: algal mats) | |
yes
|
If vegetation is visible in the wetland but you are unable to determine the type | |
no
|
If no vegetation is present in the wetland |
The keys of leaf_type=broadleaved/needleleaved and leaf_cycle=deciduous/evergreen would be used in combination with the wetland:vegetation=forested tag.
New key wetland:landform to indicate where the wetland is in context with the surrounding landscape. This tag would be applied to the areas tagged as natural=wetland.
| Key | Value | Comment |
|---|---|---|
wetland:landform
|
depression
|
The wetland is located within a depression of land so that water collects from precipitation, runoff, or groundwater |
slope
|
The wetland is located along the slope or the side of a hill | |
fringe
|
The wetland is located along the shore, bank, or edge of a permanent body of water (such as a lake, ocean, or river) | |
floodplain
|
The wetland is located within a floodplain. It may be close to permanent bodies of water, but is not directly connected to it. The wetland may periodically flood when the neighboring waterbody overflows. | |
flat
|
The wetland occupies a landscape that is predominantly flat and not near a major water body. Water on the wetland may be from precipitation, and is sometimes shallow and patchy across a large area. |
Expand the use of anthropogenic=yes to apply to wetlands to specify that the formation of the wetland is due to human activity. This tag would be applied to the areas tagged as natural=wetland. For example, a wetland flooded by a dam would be tagged as anthropogenic=yes. A wetland flooded by a beaver would not be tagged as such.
Expand the use of the salt=* tag to wetlands. For example, apply salt=yes to a wetland if the water is salty, and salt=no if the wetland contains fresh water. This tag would be applied to the areas tagged as natural=wetland.
Examples
Note: the following tables showing current and proposed tags only include the wetland-specific tags on each feature.
1. Bonneville Salt Flats in Utah
| Current | Proposed |
|---|---|
landuse=salt_pond
|
natural=wetland
|
2. Fujimae-higata (藤前干潟) wetland in Japan
| Current | Proposed |
|---|---|
natural=wetland
|
natural=wetland
|
3. Wetland in the Tigrett Wildlife Management area in Dryersburg, TN
[Insert photo]
Photo by user aidenrohde on Mapillary (image)
| Current | Proposed |
|---|---|
natural=wetland
|
natural=wetland
|
4. Unnamed wetland along the Nile River in Egypt
[Insert photo]
| Current | Proposed |
|---|---|
natural=wetland
|
natural=wetland
|
Features/Pages affected
The following wiki pages that would be affected if this proposal is approved include:
The “How to Map” section of this page would be edited to include the newly accepted tags with their descriptions, including an expansion of the “other useful generic tags” portion. The primary overview on this page would also be expanded upon, and the general formatting of the page would be improved so the additional information would be easier to digest.
The key:salt page would be edited to clarify its use when mapping wetlands, and adjust the “useful combination” section accordingly.
The anthropogenic=yes page would be edited to clarify its use when mapping wetlands.
Comments
Please comment on the discussion page.
External discussions
For more in-depth discussion regarding this proposal, please take comments and questions to the public #wetlands channel in the OpenStreetMap US Slack instance.