Riparian zones increase regional species richness by harboring different, not more, species


Riparian zones are habitats of critical conservation concern worldwide, as they are known to filter agricultural contaminants, buffer landscapes against erosion, and provide habitat for high numbers of species. Here we test the generality of the notion that riparian habitats harbor more species than adjacent upland habitats. Using previously published data collected from seven continents and including taxa ranging from Antarctic soil invertebrates to tropical rain forest lianas and primates, we show that riparian habitats do not harbor higher numbers of species, but rather support significantly different species pools altogether. In this way, riparian habitats increase regional (γ-) richness across the globe by >50%, on average. Thus conservation planners can easily increase the number of species protected in a regional portfolio by simply including a river within terrestrial biodiversity reserves. Our analysis also suggests numerous possible improvements for future studies of species richness gradients across riparian and upland habitats. First, <15% of the studies in our analysis included estimates of more than one taxonomic group of interest. Second, within a given taxonomic group, studies employed variable methodologies and sampling areas in pursuit of richness and turnover estimates. Future analyses of species richness patterns in watersheds should aim to include a more comprehensive suite of taxonomic groups and should measure richness at multiple spatial scales.








James Brendan Heffernan

Associate Professor of Ecosystem Ecology and Ecohydrology

I am interested in major changes in ecosystem structure, particularly in streams, rivers and wetlands. My work focuses on feedbacks among ecological, physical, and biogeochemical processes, and uses a wide range of tools and approaches. I am particularly interested in projects that address both basic ecological theory and pressing environmental problems. Increasingly, we are applying tools and theories developed for local ecosystems to better understand ecological patterns and mechanisms at regional and continental scales.

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