Wetland Indicator Status
The wetland indicator status is a three or four letter code that specifies the likelihood that a particular vascular plant taxon will be found within a wetland within a given region of the country. The National Wetland Plant List, which is administered by the U.S. Army Corps of Engineers (USACE), lists plant taxa potentially occurring in wetlands in the U.S. along with their associated regional wetland indicator status. USACE divides the U.S. and its territories into ten regions for the purposes of wetland evaluations. All of the New England states are located within a region called “Northcentral and Northeast” (NCNE).
Wetland indicator status codes, as defined by Lichvar (2012) are as follows:
- OBL (obligate) – Almost always occurs in wetlands
- FACW (facultative wetland) – Usually occurs in wetlands, but may occur in non-wetlands
- FAC (facultative) – Occurs in wetlands and non-wetlands
- FACU (facultative upland) – Usually occurs in non-wetlands, but may occur in wetlands
- UPL (obligate upland) – Almost never occurs in wetlands
Some plant taxa are found in more than one region, and in some cases, their wetland indicator status varies depending on the region. For example, Actaea rubra has a code of UPL in the Atlantic and Gulf Coast Plain; a code of FACU in NCNE; and a code of FAC in the Arid West.
The National Wetland Plant List specifies that species that are not included on the list should be considered UPL for wetland delineation purposes. Generally, UPL species are not listed in the National Wetland Plant List (although a few species are listed as UPL because they are rated FACU or wetter in at least one USACE region). A small number of wetland plant species may not be listed due to taxonomic discrepancies or other reasons.
Mass Nature used wetland indicator status data from the Northcentral and Northeast (NCNE) 2016 Regional Wetland Plant List. These data are from the following source:
- Lichvar, R.W., D.L. Banks,W.N. Kirchner, and N.C. Melvin. 2016. The National Wetland Plant List: 2016 wetland ratings. Phytoneuron 2016-30: 1-17. Published 28 April 2016. ISSN 2153 733X. Available from http://wetland-plants.usace.army.mil/ and from http://www.phytoneuron.net/.
Looking up a plant’s wetland indicator status on the National Wetland Plant List should be a simple and straightforward task – merely find the plant’s name on the list and next to the name you will see its region-specific indicator status. Most of the time, this task is as easy as it seems. However, in some cases, it can be difficult to find a plant’s name on the list due to taxonomic inconsistencies – a plant’s scientific name, and, in some cases, whether it is recognized as a species, as opposed to a subspecies or variety of another species, depends on the botanical authority that one uses.
Wetland indicator status values were assigned to vascular plant taxa in the Mass Nature database as follows:
- When the scientific name (or a synonym of the scientific name) in the Mass Nature database exactly matched the scientific name on the NCNE regional wetland plant list, then the corresponding wetland indicator value was used.
- When the scientific name (and any associated synonyms) failed to match any of the names on the NCNE regional wetland plant list, then the taxon was considered to be not listed.
- When the scientific name did not match any name on the NCNE regional
wetland plant list, and when synonyms of that name were either
varieties or subspecies of a name on the NCNE regional wetland plant
list, then the corresponding NCNE indicator value for the species was
used with the following exceptions:
- If another species occurs in New England whose scientific name (or associated synonyms) exactly matched the name on the NCNE regional wetland plant list, then the taxon in the Mass Nature database that only matched as a variety or subspecies of that name was considered to be not listed. For example, the Mass Nature database contains an entry for Ranunculus caricetorum (with a synonym of Ranunculus hispidus var. caricetorum). The closest corresponding entry on the NCNE regional wetland plant list is Ranunculus hispidus. However, because there is a taxon named Ranunculus hispidus in New England, the taxon called Ranunculus caricetorum was considered by Mass Nature to be not listed (lacking a wetland indicator status).
- If two or more synonyms of the scientific name in the Mass Nature database were subspecies or varieties of two or more names on the NCNE regional wetland plant list, and if the corresponding names on the NCNE list had different wetland indicator values, then the taxon was considered to be not listed. An exception was made if the corresponding names on the NCNE list could be narrowed down to one name because some exactly matched the names of other New England species. If all of the corresponding names had the same wetland indicator status, then that indicator status was used. For example, the Mass Nature database contains an entry for Viola pallens (which has synonyms of Viola macloskeyi subsp. pallens and Viola rotundifolia var. pallens). The closest corresponding names on the NCNE regional wetland plant list are Viola macloskeyi (OBL) and Viola rotundifolia (FAC). Because there is another species in New England called Viola rotundifolia (but not another species called Viola macloskeyi), Viola pallens was assigned a wetland indicator value of OBL.
Lichvar, R.W. 2012. The National Wetland Plant List. ERDC/CRREL TR-12-11. U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire.
Last edited: 15 Sept. 2017