GM4.5

Studies on geodiversity have been gaining prominent interest among the geoscientific community over the last decades. As operational concept, geodiversity implies a measurement and its application narrowed to a given spatial area. However, such concept is often integrated to support planning perspectives that focus mostly on geoconservation, neglecting other activities that might transform, destroy or exploit georesources. Furthermore, diversity alone might not account for the actual pivotal role that abiotic and interfacial components play in socio-ecological systems and their functioning.

In a first part, the present research reviews the geodiversity concept, integrated within a framework towards its operationalization for territorial management. Geodiversity is defined as the range of abiotic and interfacial resources – lithodiversity, superficial diversity, hydrodiversity, pedodiversity, geomorphodiversity, mineral diversity, paleodiversity and climate diversity – of a given area, including their constitution, assemblages, structures, properties and contributions to socio-geo-ecological systems. Geodiversity is therefore considered both in its typological and functional diversity, the latter one being related to the geo-ecosystem services (GES) that geodiversity provides to society. The characterization of geodiversity is completed with the identification of the anthropogenic drivers linked to land-planning strategies (e.g. urban projects, mining activities, agricultural practices) and that might affect, positively or negatively, GES supply.

The second part, aims at confirming the necessity of an operational framework through the assessment of geodiversity and its spatial patterns on the French Guiana case-study, an Oversea French territory located in South America, within the Guiana Shield. Almost entirely covered by the Amazon rainforest ecosystem of exceptional biodiversity, French Guiana is considered as an international conservation and land-planning challenge which faces multiple issues (e.g. urban, agricultural and industrial growth, forest management and gold mining planning). However, French Guiana geodiversity and its management are not properly acknowledged by land-planning strategies.

The assessment of geodiversity of French Guiana was performed through the creation of a 10x10 km grid in a GIS environment. Lithodiversity and superficial diversity, hydrodiversity, geomorphodiversity and mineral diversity sub-indices were assessed based on the number of entities within each grid-cell. The four sub-indices were summed to obtain a geodiversity index. Local Moran’s I was then used to identify geodiversity hotspots and coldspots.

Geodiversity hotspots were found mainly along the gold-bearing greenstone belts crossing French Guiana. However – despite the fact that further data must be integrated for soil and paleontological resources that are still little known at the scale of the whole territory – some areas showing low geodiversity are known to display important points of geological interest (from a geoheritage perspective). Therefore, this research allows to review a more comprehensive definition of geodiversity and to highlight the necessity of standardized datasets and classification methods to assess all geodiversity components. The assessment of diversity alone is not enough for geoconservation nor broader land-planning perspectives. It is pivotal to account for the contribution of geodiversity to the functioning of a given area and its interaction with anthropic activities. Geofunctionality can be assessed through proper datasets identifying and quantifying GES flows (i.e. supply-demand), for instance, through Essential Geodiversity Variables.

How to cite: Scammacca, O., Bétard, F., Heuret, A., Aertgeerts, G., and Montagne, D.: Geodiversity assessment of French Guiana: the need to integrate geodiversity within land-planning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12641, https://doi.org/10.5194/egusphere-egu22-12641, 2022.

The term geodiversity was proposed in the 1990s, however there is still a noticeable lack of established conceptual and methodological framework for geodiversity assessment. In its absence, various geodiversity assessment methods have been proposed. They can be categorized, based on data sources, into direct and indirect, and based on the assessment procedure into qualitative, quantitative, and mixed (qualitative-quantitative). Each of these categories introduces an ambiguity by relying on expert judgment or interpreted geodata rather than on direct measurement. Despite the impressive number of different terrain-specific studies, there has been a conspicuous absence of comparative studies testing the efficacy of geodiversity assessment methods across different types of terrain characterized by differences in morphology, morphogenesis, and relief energy.

Therefore, we have selected three different national parks represent different landscape types: mountains (Karkonosze National Park), uplands (Roztocze National Park), and lowlands (Wolin National Park). Input datasets included 1 m DEM and thematic map layers: lithological, geomorphological, hydrographical and soils features as well as CORINE Land Cover. The presentation reports on geodiversity assessments performed independently by experts and volunteers as crowdsourcing analytical data. A potential strength of the crowdsourcing approach over the expert-based approach is that the former minimizes subjectivism, which is a common critique of expert-based environmental valuation, including the subject of our research - geodiversity assessment. Using the DEM data and r.watershed tool, the 1-order catchments were delineated for the national parks (KNP 212, RNP 403, WNP 289) and used as spatial units for geodiversity assessment. The use of catchments instead of squares, grid cells or arbitrary polygons is a new approach in geodiversity assessments. The expert and volunteer assessment data sets were separately processed with two spatial multicriteria methods: Weighted Linear Combination (WLC) - also referred to as the global version of WLC, and Local Weighted Linear Combination (L-WLC) resulting in two geodiversity maps for each of the parks. More over we used two scenarios. Under the first scenario, called the expert-based scenario, an expert familiar with the study area or a group of experts classifies the individual abiotic components of geodiversity and assigns them weights instrumental for computing a geodiversity score. In the second scenario, called the crowdsource-based scenario, multiple individual ratings concerning the abiotic components of geodiversity and their weights are collected and aggregated to yield a corresponding geodiversity score. The maps were qualitatively evaluated for their efficacy of capturing spatial heterogeneity and differentiating between high and low geodiversity of specific areas within the national parks. The expert-based maps were compared with the volunteer-based maps using statistical measures of association and similarity: Spearman’s correlation coefficient, the Jaccard similarity index, also known as Tanimoto index, and the relative Manhattan similarity.

The results show that L-WLC is more suitable for geodiversity mapping of mountainous areas characterized by high morphogenetic and morphometric diversity whereas WLC yields better results in less diverse areas such as uplands and lowlands. The use of data originating from volunteer-based assessment requires meeting internal and external data quality standards and should be treated with caution.

How to cite: Zwoliński, Z., Najwer, A., and Jankowski, P.: Geodiversity assessment with global and local S-MCA in different landscapes based on expert and crowdsourcing data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9007, https://doi.org/10.5194/egusphere-egu22-9007, 2022.

The current state of geodiversity estimates still lack of complete strategy of assessments in comparison with its analogue, biodiversity. This issue connects with the number of differences between these terminologies and existing form of their elements. However, the basic understanding of geodiversity, which common among most researchers, is the numeric representation of the variety of abiotic elements includes geology, geomorphology, hydrology, climate, soils and other features and processes influencing non-living nature. In this research, two main elements of geodiversity (geology and geomorphology) have been assessed with two different scale systems defined as “grid” and “non-grid”. “Grid” system based on cells with side size of 2.5 km, where each cell contains an arithmetic average value of geodiversity for each region throughout the area of research (Figure). Meanwhile, “non-grid” system assesses the areas bordered by different values of geodiversity, which shows number of shapes with sizes and forms delineated by geodiversity values on the model (Figure). Both scales were calculated by qualitative-quantitative methodology of assessment of geodiversity. The methodology based on 5-point evaluation system for geological and geomorphological elements calculated by arithmetic average equation, where places with high values can be considered as potential geosites, which should be studied in detail for future research. The two islands (Upolu and Savai’i) of Western Samoa have been selected for the research due to their relatively simple geological history based on an early growth of a basaltic shield volcano(s) covered by small scoria and spatter cones formed during the post-shield rejuvenated volcanism. Even though the region is in the tropical climate zone with high rainfall, its geology provides an even relief throughout the islands, with only few short immature fluvial networks. The multiple extensive lava sheets also acted as erosion-resistant substrate further forming fluvial networks of deep but narrow canyon-like stream valleys with numerous high waterfalls. These regions are recognizable by qualitative-quantitative methodology, but differently represented on the models with mentioned scale systems (“grid” and “non-grid”). For Samoa Islands, fluvial networks are important as they expose volcanic stratigraphy and forming rugged morphological elements on the surface. Their limited geometry commonly prevents them to be clearly visible on the “grid-based” system of geodiversity assessment. Meanwhile, “non-grid” system accurately outlines these regions as locations with high values (especially Upolu Island) (Figure). In result, “grid” and “non-grid” scale systems utilized by one qualitative-quantitative methodology demonstrate different pictures: “Grid” scale system of geodiversity estimates is more suitable for a quick first order assessment of geodiversity with big databases, while “non-grid” method fits better to outline exact location with high geodiversity in a large map scale, hence more useful to highlight valuable regions for geoconservation.