The National Wetland Plant List (NWPL) has undergone its first major revision since 1988. The U.S. Army Corps of Engineers, which took over responsibility for the NWPL from the U.S. Fish and Wildlife Service (FWS) in 2006, announced that the updated list contains 8,200 species, an increase of 1,472 species from the 1988 NWPL.
Wetlands are evaluated using three factors in accordance with the 1987 Wetland Delineation Manual and Regional Supplements:
- Hydrology, and
The NWPL is used in evaluating the vegetation factor. In addition to providing a reference for wetlands delineations under the Clean Water Act, the NWPL also provides information for wetland restoration and research and the development of compensatory mitigation goals as well as providing general botanical information about wetland plants.
The Corps began the revision process in 2008. At that time, the Corps estimated that there were approximately 1,500 indicator status changes as a result of taxonomic changes (lumping and splitting of species) in the previous 20 years. In addition, more field knowledge and scientific information had been published for many wetland species. The Corps set up a voting process that led to 16,642 votes cast for 5,315 species. The process also involved 12 rounds of review by regional and national panels. In total, according to the Corps, over 130,000 comments and votes were received and reviewed.
The NWPL assigns an indicator status to each wetland plants. An indicator status reflects the likelihood that a particular plant occurs in a wetland or upland. The five indicator statusesare:
- Obligate (OBL) plants that always occur in standing water or in saturated soils
- Facultative wet (FACW) plants that nearly always occur in areas of prolonged flooding or require standing water or saturated soils but may, on rare occasions, occur in non-wetlands
- Facultative (FAC) plants that occur in a variety of habitats, including wetland and mesic to xeric non-wetland habitats but commonly occur in standing water or saturated soils
- Facultative upland (FACU) plants that typically occur in xeric or mesic non-wetland habitats but may frequently occur in standing water or saturated soils
- Upland (UPL) plants that almost never occur in water or saturated soils.
Plant data in the NWPL are organized into 10 regions that coincide with Corps wetland delineation regions.
In addition to the Corps, three other federal bodies – FWS, EPA, and the Natural Resource Conservation Service – will use the updated NWPL on all new jurisdictional wetlands determinations performed after June 1, 2012.
The Corps' final notice announcing the update was published in the May 9, 2012, FR.