THE GEODIVERSITY INDEX MAP OF PUERTO RICO – A PRACTICAL REFERENCE IN LAND DEVELOPMENT AND ENVIRONMENTAL CONSERVATION

Geodiversity represents the abiotic counterpart of biodiversity; it encompasses the geological, geomorphological, pedological, paleontological, hydrological and mineralogical features, assemblages, properties and systems. The quantification and mapping of geodiversity have a wide application in various fields of sustainable development and nature conservation, and most often take the form of a Geodiversity Index as a compilation of partial indices – one for every segment of abiotic nature.

The Index for Puerto Rico was assessed and mapped using ArcGIS and QGIS software, and a SRTM Digital Elevation Model. The methodology is straightforward and involves a simple algorithm, but relies and depends on pre-existing thematic maps. These are overlapped with a grid and the number of units in each grid cell is extracted following a semi-automatic process. The values of the partial indices are summed and accommodated into a 5-grade (low-high) scale. The resulting raster model is accessible to and can be interpreted by a wide range of people with little or no background in geosciences.

The Geological Index was obtained from geologic provinces, lithostratigraphic formations and lithodemic units, and major depositional and structural contacts. The Geomorphological Index was based on physiographic units and geoclimatic zones. The Pedological Index was obtained from soil orders. The Hydrological Index is represented by hydrology and hydrogeology – surface water bodies, rivers and watersheds, ground water provinces and aquifers. The Paleontological Index was given by fossiliferous stratigraphic units. The Mineralogical Index was given by the spatial distribution of metallic and non-metallic mineral resources.

Puerto Rico has well-defined areas of high and very high geodiversity that are vulnerable to the rapid expansion of built-up land, and contrast with the almost exclusive focus on biodiversity of the existing protected areas. To better illustrate this, the Geodiversity Index map is displayed against a map of urban and rural land use and the map of Natural Protected Areas.

This study reinforces the need for more efficient land-use planning across the main island of Puerto Rico and for an integrated approach of biodiversity and geodiversity for conservation purposes.