Comments 238 Conservation Biology, Pages 238–243 Volume 16, No. 1, February 2002 Ecoregions in Ascendance: Reply to Jepson and Whittaker ERIC WIKRAMANAYAKE,* ERIC DINERSTEIN,* COLBY LOUCKS,* DAVID OLSON,* JOHN MORRISON,* JOHN LAMOREUX,* MEGHAN MCKNIGHT,* AND PRASHANT HEDAO† *Conservation Science Program, World Wildlife Fund – United States, 1250 24th Street NW, Washington, D.C. 20037, U.S.A. †Environmental Systems Research Institute, Inc., Redlands, CA 92373, U.S.A. Introduction In their essay, Jepson and Whittaker (2002 [this issue]) express three aims: (1) to place the World Wildlife Fund ( WWF ) ecoregions (Olson et al. 2001; Wikramanayake et al. 2001) in context with alternative systems for set- ting conservation priorities; (2) to express concern about the explicitness, transparency, and repeatability of the methods employed to define and delineate ecoregions; and (3) to ask whether the WWF ecoregions improve upon existing schemes of representing biodiversity (which they attempt to investigate by performing a qualitative test with Indonesia as a case study). Their essay contains a number of misrepresentations of our ecoregion approach. In the interest of brevity, we address only the major issues in this reply. We begin by arguing for the value of ecoregions, outlining the ratio- nale behind the ecoregion framework and the delinea- tion process, and comparing these with other efforts. The approach is detailed explicitly by Wikramanayake et al. (2001) and others ( Ricketts et al. 1999; Abell et al. 2000; Dinerstein et al. 2000). Why Ecoregions? Ecoregions may be a relatively new concept in conserva- tion biology, but they are based on classical biogeogra- phy. Although a single institution like WWF may actually produce an ecoregion map, the ecoregions themselves are developed through extensive collaboration with bio- geographers, taxonomists, conservation biologists, and ecologists from around the world. Since 1999, three of the leading international nongovernmental organizations— WWF, The Nature Conservancy ( TNC ), and Conservation International (CI )—and many other conservation partners around the world have identified ecoregions or larger bio- geographic units such as hotspots (CI ) as an appropriate scale for conservation priority setting and planning. These organizations have found that ecoregions provide the crit- ical spatial link between global priority-setting efforts and site-based assessments. Perhaps the most attractive feature of ecoregions is that they define biogeographic units that are most suit- able for meeting a fundamental goal of biodiversity con- servation: the representation of all habitats and distinct biotas in networks of conservation areas. The use of eco- regions allows us to avoid redundancy and enhance com- plementarity in the design of reserve networks better than do approaches that rely on political units to deter- mine conservation priorities. Developing conservation strategies within a framework of ecoregions also allows us to address the ecological processes that maintain bio- diversity and to protect populations of species with large spatial needs that cannot be accommodated at the site scale or that do not adhere to political boundaries ( Din- erstein et al. 2000; Groves et al. 2000; Mace et al. 2000). The magnitude of the shift to ecoregions for conserva- tion planning is worth noting for the benefit of conser- vation biologists unaware of this trend. The WWF has targeted 189 of the planet’s 867 terrestrial ecoregions, 15 freshwater ecoregions, and 24 marine ecoregions for such analyses. Within a few years, TNC plans to finish ecoregion strategies for all 62 of its U.S. ecoregions, and CI plans to complete similar analyses for all 25 hotspots ( Myers et al. 2000), many of which overlap with the Global 200 Ecore- gions identified by WWF (Olson & Dinerstein 1998). The Address correspondence to E. Dinerstein, email eric.dinerstein@ wwfus.org Paper submitted August 13, 2001; revised manuscript accepted Au- gust 20, 2001.