Towards a comprehensive geodiversity assessment with a versatile GRASS GIS module: r.geodiversity

Geodiversity has a recognized role in geoheritage management, conservation strategies, and in providing ecosystem services for the benefit of the environment and society. In the scientific literature, there is little consensus about practical assessment of geodiversity. A clear–cut, quantitative, and operational definition would help elucidating its role in supporting biodiversity and informing territorial planning. We introduced a new software module to produce a wide range of diversity indices, specifically designed to study geodiversity in an incremental way. The module considers a minimal set of geomorphometric surface descriptors and lithology, and performs a basic assessment of geomorphodiversity, as a first approximation to geodiversity. The software can use additional layers in combination with the default ones, with great flexibility for what concerns the type of input, their relative weights in the final assessment, the possibility of choosing a multi–scale gridded output or a polygonal output, and other options discussed in detail this work. We show that the geomorphodiversity index obtained with the new software module compares with Shannon diversity in a non-trivial way, in an assessment within 325,578 polygonal domains all over Italy. The result suggests that the new index is meaningful, with the advantage of a simple definition. Finally, we show that a diversity index enriched with soil type data shifts the distribution of diversity classes in an counterintuitive way. We argue that such a comprehensive definition of geodiversity can be used to inform sustainable land management, protect unique natural heritage, and sets a baseline to study the abiotic support to biodiversity in a quantitative way.