A team of biologists developed an ecological land classification system for the World Wide Fund for Nature ( WWF ) that identified 14 biomes , called major habitat types , and further divided the world 's land area into 867 terrestrial ecoregions . A team of biologists convened by the World Wide Fund for Nature ( WWF ) developed an ecological land classification system that identified fourteen biomes , called major habitat types , and further divided the world 's land area into 867 terrestrial ecoregions .