An ecoregion is a relatively large unit of land or ocean that contains geographically distinct assemblage of natural communities with boundaries that approximate the original extent of natural communities prior to major land use change. Ecoregions:
- share a large majority of their species and ecological dynamics;
- share similar environmental conditions, and;
- interact ecologically in ways that are critical for their long-term persistence.
The motivation for the ecoregion classification system is that scarce resources and dwindling time force conservationists to target their actions to stem the loss of biodiversity — a pragmatic approach, given the highly uneven distribution of species and threats. Unfortunately, the ability to focus strategically is hindered by the absence of a global biodiversity map with sufficient biogeographic resolution to accurately reflect the complex distribution of the Earth’s natural communities. Without such a map, many distinctive biotas remain unrecognized.
Ecoregions reflect the distribution of a broad range of fauna and flora across the entire planet, from the vast Sahara Desert to the diminutive Clipperton Island (eastern Pacific Ocean). They are classified with a system familiar to all biologists: biogeographic realms and biomes. Ecoregions, representing distinct biotas, are nested within the biomes and realms and, together, these provide a framework for comparisons among units and the identification of representative habitats and species assemblages.
World Wildlife Fund (WWF) Classification
The WWF system subvides the terrestrial world into 14 biomes and eight biogeographic realms (Figure 1). Nested within these are 867 ecoregions (Figure 2). WWF has assessed these ecoregions and identified the Global 200 -- the most biologically distinct terrestrial, freshwater, and marine ecoregions of the planet.
- Eric D. Wikramanayake. 2002. Terrestrial ecoregions of the Indo-Pacific: a conservation assessment. Island Press. 643 pages
- Robin A. Abell. 2000. Freshwater ecoregions of North America: a conservation assessment. World Wildlife Fund. Island Press. 639 pages