Intensification of land use practices and climate change has resulted in extensive wetland loss and declines of native submersed aquatic vegetation (SAV) from wetlands across North America. Although SAV is an important diet component of many species of waterfowl (e.g., gadwall [Mareca strepera]) and other waterbirds (e.g., American coot [Fulica americana]), it has been dismissed as an important contributor to energetic carrying capacity due to assumed low density and assimilable energy. Moreover, conservation planners currently are unable to accurately account for the energetic contribution of SAV in bioenergetics models because of a lack of biomass and energy estimates for semi-permanent wetlands. Following recent advancements in assimable energy estimates for many common SAV species, we estimated energetic carrying capacity of 21 semi-permanent wetlands containing SAV identified as important stopover locations for migrating waterfowl and other waterbirds in the Midwest, USA. Energy density of SAV (x = 813 ± 257 EUD/ha) was generally less than managed wetland types, varied by National Wetland Inventory class, and had a great degree of annual (± 984,873 EUD/ha) and spatial variation (± 87,970 EUD/ha). Energetic carrying capacity was greatest for isolated wetlands (1,507,584 585,219 EUD), followed by wetlands connected to rivers (840,286 549,395 EUD) and lakes (205,516 59,903 EUD). We attempted to develop a visual rapid assessment index that would allow wetland managers or researchers to quickly estimate energy density from SAV, but correspondence was moderate (R2m = 0.43). Energetic carrying capacity estimates of wetlands containing SAV will allow conservation planners to more precisely estimate energy supply on the landscape for waterfowl and wetland managers to evaluate trade-offs among alternative management strategies. We suggest future research estimate energy density among randomly selected wetlands across the Midwest and collect additional information on the below-ground biomass of SAV and associated assimilable energy.
|Title of host publication
|81st Midwest Fish and Wildlife Conference
|Published - 2021