Developed originally by Olson, D. M. and E. Dinerstein (2002), Bailey (1995) and Environment Canada (Wiken, 1986), these data layers were modified by The Nature Conservancy (TNC) to be used in its Biodiversity Planning exercises in the process known as Ecoregional Assessments. Several Ecoregions were modified from the originals by TNC staff developing the aforementioned assessments. The modifications are based on ecological, bio-physical and political rationales; most changes are noted in the accompanying documentation (attributes). Ecoregions in Canada and Mexico were modified mainly at the border with US territory, where TNC modified-Bailey (1995) ecoregions crossed over the country boundaries and the Olson, D. M. and E. Dinerstein (2002) and (Wiken, 1986) were replaced where the TNC modified-Bailey (1995) overlayed them. This layer was split from the terrestrial ecoregional assessment layer in June 2008.
Supplemental information: Download this data, and a log of changes at http://maps.tnc.org/