Abundance of rivers and wetlands, by freshwater ecoregion. The abundance of rivers and wetlands describes the degree to which a freshwater ecoregion is covered with these habitats. We calculated this abundance by combining selected classes of the Global Lakes and Wetlands Database (Level 3 of Lehner and Döll 2004), together with ESRI Rivers (2005) and the perennial rivers from ArcWorld 1:3million (ESRI 1992), all gridded to one-kilometer cell resolution. It should be noted that some ecoregions (e.g., Australia’s Arafura and Carpentaria Drainages and Great Diving Range on the northern and eastern coasts) are dominated by small rivers and streams that are not reflected properly in global river and wetland data sets; thus, abundance in these ecoregions may be underrepresented. We classified an ecoregion as “dominated by lakes and reservoirs” when it met thresholds set by regions of known lake and reservoir dominance versus river and wetland dominance. Known ecoregions were used to determine the algorithms to set the cutoffs between abundance classes. These data were derived by The Nature Conservancy, and were displayed in a map published in The Atlas of Global Conservation (Hoekstra et al., University of California Press, 2010). More information at http://nature.org/atlas. Data derived from: ESRI 1992 and 2005. ESRI ArcWorld Database [CD] and ESRI Data & Maps [CD]. Redlands, CA: Environmental Systems Research Institute. Digital media. Lehner, B., and P. Döll. 2004. Development and validation of a global database of lakes, reservoirs and wetlands. Journal of Hydrology 296: 1-22. These data were derived by The Nature Conservancy, and were displayed in a map published in The Atlas of Global Conservation (Hoekstra et al., University of California Press, 2010). More information at http://nature.org/atlas. For more about The Atlas of Global Conservation check out the web map (which includes links to download spatial data and view metadata) at http://maps.tnc.org/globalmaps.html. You can also read more detail about the Atlas at http://www.nature.org/science-in-action/leading-with-science/conservation-atlas.xml, or buy the book at http://www.ucpress.edu/book.php?isbn=9780520262560