 The common measure, species richness, illustrates the different perspectives. The pre-history of biodiversity, reflecting the species extinction crisis and the values of variety, provides a core rationale for a definition that includes counting-up species. In contrast, Koricheva and Siipi (2004) argue that popularity of species richness (as a measure) continues simply because it is understandable, measurable, and it uses available information (see also Sarkar 2019). A section below (“the Conservation Biology framing”) returns to this issue, in considering a perspective that assumes that the “biodiversity” concept arose as part of the new discipline of conservation biology in the mid-1980s.