A simple method used to identify areas of high conservation priority is the selection of countries according to highest species richness. Among the top 12 countries identified this way based on the assessment of vertebrates, swallow-tailed butterflies and higher plants are Mexico, Columbia, Ecuador, Peru, Brazil, Zaire, Madagascar, China, India, Malaysia, Indonesia and Australia. It is estimated that 70% of the species diversity in the world is found within these countries.

This method, however, involves species inventory within a geopolitical boundary, and fails to take into account the uniqueness of the fauna and flora of each country or region in question. As a result, there is considerable overlap of species between adjacent regions (or countries) that are prioritised for conservation action. For example, most mammalian species listed for Ecuador are also found in Peru. If both countries are prioritised for conservation, therefore, the same species will be conserved in both.