A useful dimension for understanding the natural systems is biological diversity or biodiversity. Biodiversity evaluates the number of species in a specific space and time period, in other words species richness.

Species richness is estimated based on biological inventories that record data referring to where and when biological organisms have been observed. It is a good idea to bring together many observations in order to provide a good representation of the biodiversity in a specific space. The time sequence of inventories in a determined space is known as a monitoring project.