Background: Primary biodiversity records (PBR) are essential in many areas of scientific research as they document the biodiversity through time and space. However, concerns about PBR quality and fitness-for-use have grown, especially as derived from taxonomical, geographical and sampling effort biases. Nonetheless, the temporal bias stemming from data ageing has received less attention. We examine the effect of changes in land use in the information currentness, and therefore data obsolescence, in biodiversity databases.
Methods: We created maps of land use changes for three periods (1956-1985, 1985-2000 and 2000-2012) at 5-kilometres resolution. For each cell we calculated the percentage of land use change within each period. We then overlaid distribution data about small mammals, and classified each data as 'non-obsolete or 'obsolete,' depending on both the amount of land use changes in the cell, and whether changes occurred at or after the data sampling's date.
Results: A total of 14,528 records out of the initial 59,677 turned out to be non-obsolete after taking into account the changes in the land uses in Navarra. These obsolete data existed in 115 of the 156 cells analysed. Furthermore, more than one half of the remaining cells holding non-obsolete records had not been visited at least for the last fifteen years.
Conclusion: Land use changes challenge the actual information obtainable from biodiversity datasets and therefore its potential uses. With the passage of time, one can expect a steady increase in the availability and use of biological records-but not without them becoming older and likely to be obsolete by land uses changes. Therefore, it becomes necessary to assess records' obsolescence, as it may jeopardize the knowledge and perception of biodiversity patterns.
Keywords: Biodiversity datasets; Historical records; Land use changes; Obsolescence; Primary biodiversity records; Small mammals; Temporal bias.