Midwest Fish & Wildlife Conference 2018

AUTHORS. Bram H. F. Verheijen, Kansas Cooperative Fish and Wildlife Unit, Kansas State University; Dana M. Varner, Rainwater Basin Joint Venture, U.S. Geological Survey, Nebraska Cooperative Fish and Wildlife Research Unit, University of Nebraska-Lincoln; David A. Haukos, U.S. Geological Survey, Kansas Cooperative Fish and Wildlife Research Unit, Kansas State University

ABSTRACT. The Rainwater Basin in Nebraska supports a complex network of spatially-isolated shallow wetlands that harbors diverse floral and faunal communities. Since European settlement, many wetlands have been lost to the network due to drainage, deliberate filling, land-use change, and increased sedimentation rates, thereby reducing the total available number and area of extant wetlands, and increasing the distance among remaining wetlands. Many species of plants, insects, and amphibians rely on these wetlands for reproduction and survival, but have limited dispersal capabilities. As a result, populations may become isolated if distances among wetlands become too large. Unfortunately, effects of the large-scale wetland losses on network connectivity remain unknown. Here, we compared network characteristics between the historical network and currently remaining wetlands in the Rainwater Basin to assess effects of the large-scale loss of wetlands on connectivity of the network at a range of allowed dispersal distances. We found that the number of functioning wetlands has decreased with more than 90% over the past century; however, losses were relatively evenly distributed throughout the network. Wetland losses had large consequences for network connectivity by increasing the dispersal capabilities necessary to travel throughout the whole network from 3.5 to 10.0 km. Last, we found that the relative importance of individual wetlands on network connectivity was strongly dependent on the allowed dispersal distance. Our study shows that large-scale losses of wetlands in the Rainwater Basin have substantially reduced network connectivity, and limited the ability of many taxa with low dispersal capacity to travel throughout the whole network. A lack of connectivity could lead to isolation of populations and increased localized extinction rates. Conservation efforts should therefore focus on maintaining or increasing the connectivity of the network. However, which wetlands should be prioritized is likely dependent on the dispersal capabilities of the species or taxa of interest.