Geodiversity Assessment of French Guiana: Challenges and Implications for Sustainable Land Planning

As operational concept, geodiversity implies a measurement and its application narrowed to a given spatial area, allowing the identification of clusters for prioritization and planning purposes. This study proposes a first geodiversity index assessment for French Guiana, a French Oversea territory located within the Guiana Shield (South America). Almost entirely covered by the Amazon rainforest associated with an exceptional biodiversity, French Guiana appears as an international conservation and land planning challenge facing multiple issues (e.g., urban, agricultural and industrial growth, forest management, mining planning). Geodiversity assessment is performed through a grid-based approach. A geodiversity index is calculated as the sum of four subindices (lithodiversity and unlithified diversity, mineral diversity, hydrodiversity, geomorphodiversity). The index calculation is based on the number of entities within each grid-cell. Spatial correlation is used to identify geodiversity clusters and finally the index is aggregated at different spatial units relevant for land planning (e.g., municipalities, hydrographic sectors, areas of ecological interest, the Guiana Amazonian Park, and the Departmental Mining Plan). The results show that the geodiversity index is mainly controlled by lithodiversity and that high geodiversity clusters are located along the gold-bearing greenstone belts crossing the territory. However, spatialized data concerning geodiversity are still inadequate or unavailable to perform proper operational assessments in French Guiana. Furthermore, based on qualitative examples, we discuss that the assessment of diversity alone might not be always enough for geoconservation nor land planning perspectives. It is pivotal to account for the geonfunctionality- i.e., the contribution of geodiversity to the functioning of socio-ecological systems-and its interaction with anthropic activities.