Measuring the temporal quality of a biodiversity database

In the context of climate change it is important to keep biodiversity databases up-to-date. This priority generates the need for a metric to assess the concept of up-to-dateness. The objective of this paper is to devise a measure of up-to-dateness for atlas-type biodiversity data. The data input into the algorithm consists of the species, date and grid cell allocation of all available records for a taxon in a region. First, for each grid cell in a region, the median of the date of the most recent record of each species is calculated. Secondly, the median of the median dates for each grid cell yields an overall measure of up-to-dateness. The performance of this algorithm is investigated in relation to databases for six taxa in southern Africa. In June 2021, the up-to-dateness of the databases varied from 41 years for the reptile database to two years for the bird database. The quality of a biodiversity database is a multidimensional concept; up-to-dateness is only one of several dimensions. The paper identifies a need to quantify the rate at which the "value" of a record decays as evidence that a species still occurs at a locality, and suggests an experimental process for doing this. The use of the up-to-dateness index to motivate citizen scientists is discussed.