Basis for Former Listing
Sparganium glomeratum is considered a circumboreal species, meaning it occurs in boreal regions around the world. Although this is true, it is perhaps misleading. The species is actually rare or absent from most of the boreal regions of the world, being common only in parts of northern Europe and Asia. In North America, it is found at several locations in Minnesota, a few sites in adjacent Wisconsin, and at scattered sites across Canada.
In fact, it appears there are more records of S. glomeratum from Minnesota than from the rest of North America combined. Current data would suggest that Minnesota is the North American stronghold of this species. However, it is quite likely that Minnesota botanists have simply done a more thorough job of finding this species. This puts conservation of S. glomeratum in Minnesota in a different perspective. Usually when Minnesota is at the edge of a species' range, the concern is how to protect the small outlier or disjunct populations. In this case, trying to protect the small core population is the issue. Sparganium glomeratum was listed as an endangered species in Minnesota in 1984. Several new records for this species led to it being reclassified as special concern in 1996.
Basis for Delisting
Since 1996, the known populations of S. glomeratum have more than doubled and the type of habitats it has been documented in, none of which are particularly threatened, has broadened greatly. It is now understood to be much more common and widespread than it was once thought to be and special concern status is no longer necessary. Sparganium glomeratum was delisted in 2013.