Geodiversity uniqueness as a new approach to quantifying geofeature patterns

This far, quantitative assessments of geodiversity have typically been conducted on the level of alpha geodiversity (i.e., the variety of geofeatures, such as rock types or landforms, in a location) or gamma geodiversity (i.e., sum of all geofeatures across all surveyed locations in a region of interest). These assessments give valuable information of the distribution of geodiversity but do not provide evidence on the uniqueness of the elements of geodiversity (i.e., geofeatures) at different sites. Uniqueness measures can be used to rank locations based on how exceptional they are in terms of geofeatures and when compared with other locations surveyed in a study.

In this study, we demonstrate a quantitative approach to distinguish how study sites differ in their geofeature uniqueness. The methodology has been originally proposed for quantifying taxonomic uniqueness in biotic communities but we here extend its use to a geodiversity context. To illustrate the approach, we have identified geological, hydrological and geomorphological geofeatures from three areas (Rekijoki, Oulanka and Paistunturit) located across Finland, and calculated the presence/absence of each geofeature in 500 m grid cells. Founded on these grid-based datasets that cover the three study areas, we have made geodiversity uniqueness calculations. First, we calculated total beta geodiversity, from which local contribution to beta geodiversity (LCBD-g) value for each site can be subsequently derived. The LCBD-g value describes the geofeature uniqueness of each site in comparison to other sites studied in an area. Second, we calculated contributions to beta geodiversity values for each geofeature (geofeature contribution to beta geodiversity, GFCBD), describing the importance of each geofeature for geodiversity variation in the studied sites.

Our results show that the uniqueness of geofeatures (LCBD-g values) varies profoundly in each of the studied areas and sites. Also, the importance of each geofeature for geodiversity variation (GFCBD value) exhibits distinct patterns, representing the varying significance of each geofeature for the total geodiversity in the studied areas. The results, especially when displayed as maps, are heuristic and an easily applicable way to flag sites that are unique in their geofeature composition. This information can complement previous approaches (such as geosite or biodiversity assessments) when prioritizing areas for nature conservation.