Terrestrial Ecoregions of the World (2001)
In "Terrestrial Ecosystems of the World" (2001), Olson et al. (2001) identified
- 8 biogeographic realms,
- 14 biomes and
- 867 ecoregions
They defined the biogeographic unit "ecoregions" as relatively large units of land, containing a distinct assemblage of natural communities and species, with boundaries that approximate the original extent of natural communities prior to major land-use change.
They argue that ecoregions provide:
- "a map with enough detail to be useful in global and regional conservation priority-setting and planning efforts,
- a logical biogeographic framework for the development of large-scale conservation strategies,
- a map and descriptions for those working to increase biogeographic literacy and to illustrate conservation issues around the world,
- a framework for a global species database useful in priority setting and ecological analyses."
The motivation behind this was the inability for a strategic conservation focus due to the "absence of a global biodiversity map with sufficient biogeographic resolution to accurately reflect the complex distribution of the Earth’s natural communities."
The current ecoregions system fuels conservation work and was developed by the WWF's Conservation Science Program.
Papua New Guinea was a good example of this. Represented in previous schemes as a single biotic region, the new mapping reflected 12 ecoregions:
- 4 lowland,
- 4 montane
- alpine scrub,
- mangrove,
- freshwater swamp and
- savannah-grassland.
But they also warn that 'no single biogeographic framework is optimal for all taxa and ecoregions reflect the best compromise for as many taxa as possible. Boundaries rarely form abrupt edges but are bound by ecotones and mosaic habitats and most ecoregions contain habitats that differ from their asigned biome, e.g. Amazonia rainforests often contain small edaphic savannas.'
At WWF's Conservation Science Program's Terrestrial Ecoregions of the World: A New Map of Life on Earth, you can see the applications of this rigorous exercise and dowload the original paper.
Similarly, a new biogeographic classification for the world’s coastal and shelf areas was drawn up by another team led by WWF and Nature Conservancy who published the marine equivalent only just earlier this year - "Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas.". This paper is also available for download.