Geographically Isolated Wetlands: Rethinking a Misnomer

Abstract

We explore the category Bgeographically isolated wetlands^(GIWs; i.e., wetlands completely surrounded by uplands at the local scale) as used in the wetland sciences. As currently used, the GIW category (1) hampers scientific efforts by obscuring important hydrological and ecological differences among multiple wetland functional types, (2) aggregates wetlands in a manner not reflective of regulatory and management information needs, (3) implies wetlands so described are in some way Bisolated,^an often incorrect implication, (4) is inconsistent with more broadly used and accepted concepts of Bgeographic isolation,^and (5) has injected unnecessary confusion into scientific investigations and discussions. Instead, we suggest other wetland classification systems offer more informative alternatives. For example, hydrogeomorphic (HGM) classes based on wellestablished scientific definitions account for wetland functional diversity thereby facilitating explorations into questions of connectivity without an a priori designation of Bisolation.^Additionally, an HGM-type approach could be used in combination with terms reflective of current regulatory or policymaking needs. For those rare cases in which the condition of being surrounded by uplands is the relevant distinguishing characteristic, use of terminology that does not unnecessarily imply isolation (e.g., Bupland embedded wetlands^) would help alleviate much confusion caused by the Bgeographically isolated wetlands^misnomer.

Biogeochemical hotspots: Role of small water bodies in landscape nutrient processing

“…GIWs are defined as wetland systems that do not have an apparent surface connection to a nearby water body (such as a river or lake) and thus are completely surrounded by uplands [Leibowitz, 2015]; however, it should be noted that many GIWs are connected through subsurface pathways or are seasonally connected for a portion of the year and form wetland complexes and thus are not 'visibly' connected or deemed to be useful [Leibowitz and Vining, 2003;Johnson et al, 2010]. Many distinct wetland systems fall under this category such as vernal pools in forests, the playa formations in the southwestern US, desert spring wetlands, the coastal Carolina and Delmarva bays, cypress domes, ponds, and wetlands of the Prairie Pothole Regionmany of which tend to be small systems in the landscape [Tiner, 2003;Mushet et al, 2015]. There has been criticisms of the GIW and 'significant' terminology as it precludes the idea of "connectivity continua," as systems may have different degrees of connectivity in hydrological, biogeochemical and ecological connection.…”

“…There has been criticisms of the GIW and 'significant' terminology as it precludes the idea of "connectivity continua," as systems may have different degrees of connectivity in hydrological, biogeochemical and ecological connection. The term GIW implies that these systems are functionally isolated from the landscape [Mushet et al, 2015]; 'significant wetlands' are implied to be the only systems to be truly beneficial A growing number of recent studies have begun to explore the collective effect of wetlands in landscapes but with a growing emphasis on the role of size, location, and type on its functionality in hydrological, biogeochemical, and ecological cycles.…”

Do geographically isolated wetlands influence landscape functions?

“…GIWs are not hydrologically, biogeochemically, or biologically isolated (43) from other landscape elements or downstream waters. Rather, they span the entire continuum of landscape connectivity, varying in mode, timing, duration, and magnitude (44), with antecedent moisture, geology, topography, land cover, and the specific material or organism. However, lack of persistent surface water connectivity to other elements means they occupy the lower end of the connectivity continuum, with functions controlled by episodic or slow transport of water and solutes, or constrained dispersal of organisms.…”

“…However, lack of persistent surface water connectivity to other elements means they occupy the lower end of the connectivity continuum, with functions controlled by episodic or slow transport of water and solutes, or constrained dispersal of organisms. Unambiguous generalizations about GIW connectivity with downstream waters are untenable, leading some (44) to argue the term is misleading. We retain it here as the default term since 2002 because proximity to drainage features informs our analyses and because it broadly represents wetlands imperiled by recent judicial interpretations of US Clean Water Act jurisdiction.…”

Delineating wetland catchments and modeling hydrologic connectivity using lidar data and aerial imagery

“…Concerns over flooding along rivers in the PPR have stimulated the development of hydrologic models to simulate the effects of depression storage on peak river flows (Hubbard and Linder, 1986;Gleason et al, 2007;Gleason et al, 2008;Huang et al, 2011b). Since most of these prairie wetlands do not have surface outlets or welldefined surface water connections, they are generally considered as geographically isolated wetlands (GIWs) or uplandembedded wetlands (Tiner, 2003;Mushet et al, 2015;Cohen et al, 2016;Lane and D'Amico, 2016). Recently, the US Environmental Protection Agency conducted a comprehensive review of over 1350 peer-reviewed papers with the aim of synthesizing existing scientific understanding of how wetlands and streams affect the physical, chemical, and biological integrity of downstream waters (US EPA, 2015).…”