The importance of the subindices on quantitative assessment of geodiversity: a methodological discussion and application to the Geopark Costões e Lagunas, SE Brazil

The last decades witnessed methodological advances concerning the creation of quantitative geodiversity maps, which represent the quantity and spatial distribution of abiotic elements. However, there are still issues regarding the creation of these maps. This work presents the geodiversity index map of the Geopark Costões e Lagunas, located in Rio de Janeiro State, Brazil. The map was generated through four subindices: lithological, geomorphological, pedological, and hydrological. The quantification method involved overlaying a regular grid (2,5 × 2,5 km grid cells) onto thematic maps representing the subindices, which is the most common method to generate geodiversity index maps. This resulted in five maps: geodiversity index, and the four subindex maps. We argue that the subindices should not be simply used as steps to achieve the final product, since they are relevant on their own. Therefore, attention should be given both to the methodological procedures for their creation and to the generated results. The manuscript discusses the selection of subindices; potential errors for counting a single element more than once; the notion that a geodiversity index map may hide areas that are important due to specific components; and the importance of using subindex maps as relevant results and not only as secondary products. These discussions are intended to contribute to the methodological consolidation concerning the creation of geodiversity index maps, which are acknowledged as important environmental management tools for displaying the richness and spatial distribution of the abiotic environment.