'Biological diversity' refers to the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems (CBD 1992). A large number of ways have been devised to assess these values following the entry into force of the Convention on Biological Diversity (CBD) in 1993. Over time, and as computer power has increased and become affordable for almost all researchers, these measures have tended to become more sophisticated and require larger amounts of data and computing power, which has gone hand in hand with the development of global databases on species distribution, point localities, habitat and DNA phylogenies.

In this review we have assessed the various approaches to measuring biodiversity at the species level and developing models that can be used to assess the present patterns and project these into the future against possible scenarios.