Joseph E. Gerken

Human Impact on Freshwater Ecosystem Services: A Global Perspective

Human environmental change influences freshwaters as well as the regulating, provisioning, and cultural services that ecosystems provide worldwide. Here, we assess the global human impact on the potential value of six freshwater ecosystem services (ES) and estimate the proportion of each used globally (the mean value across all countries is in parentheses): biodiversity (0.37), disturbance regulation (0.24), commodities (0.39), greenhouse gases (0.09), water availability (0.10), and water quality (0.33). We also created a composite index of the impact. Using different valuation schemes, we found that humans have used potential global freshwater ES scaled by a relative value of roughly 4-20%, with a median of 16%. All countries use a considerable amount of the potential ES value, invalidating the idea that wealthier countries have less impact on their ES once they have developed. The data suggest that humans have diminished the potential ES provided by freshwaters across the globe and that factors associated with high population growth rates are related to the overall degradation.

Fish assemblage and habitat factors associated with the distribution of Topeka shiner (Notropis topeka) in Kansas streams

Topeka shiners (Notropis topeka) were historically abundant throughout many Great Plains streams but their abundance and distribution declined and the species was listed as federally endangered in 1999. However, few studies have examined how Topeka shiner populations are linked to biotic and abiotic factors. Thus, the objectives of this study were to identify trends in Topeka shiner distribution from 1995 to 2008 and determine which fish assemblage and habitat factors were most associated with Topeka shiner distribution in Kansas streams. Fish and in-stream habitat metrics were collected from 34 sites in northeast Kansas in 1995, 2003, and 2008. Stepwise discriminant function analyses (DFA) were used to determine if fish assemblage percent composition and in-stream and landscape habitat factors could be used to differentiate among years and between sites with and without Topeka shiners. Higher percent composition of rosyface shiner (Notropis rubellus) was generally indicative of sites with Topeka shiners whereas higher relative abundance of central stoneroller (Campostoma anomalum) and largemouth bass (Micropterus salmoides) were associated with sites without Topeka shiners. Sites with Topeka shiners also tended to have more gravel substrate and greater mean stream length, whereas sites without Topeka shiners generally had higher proportional impoundment area and proportional urban land area. These findings suggest that anthropogenic alteration of habitat in and around streams with Topeka shiners may facilitate their declines and establishment of non-native or generalist fishes. Our results may help managers identify habitats with the greatest need for protection or restoration and may help protect Topeka shiner populations from further population declines.