Geomorphology significance for the evaluation of geodiversity-biodiversity correlation. Preliminary results from Rome urban area (Italy)

According to the definition of the ‘‘Rome ecosystem’’ first proposed by Giacomini (ref. in Blasi et al., 2008), more than 10 years ago a Rome Biosphere Reserve was imagined in the context of an interdisciplinary project, involving landscape ecologists, geologists, plant ecologists, zoologists, geographers, city planners and environmental psychologists. The project was a pilot experience, afterward it evolved deepening the knowledge of land use changes over time, the floristic, vegetational, and ecological territorial analyses, and the planning of green infrastructures based on biodiversity and ecosystem services.

Geodiversity studies were since the beginning supporting ecological land classification for biodiversity monitoring and conservation purposes. Land units are fundamental for the assessment of the natural heterogeneity of an area, defined by climatic, abiotic and biotic parameters, which allows the assessment of potential natural biodiversity (in the sense of ecosystem diversity). Subsequently, the comparison with the real heterogeneity and the real biodiversity, allows the planning of conservation actions and restoration interventions.

In particular land units’ hierarchical divisive classification (top-down) uses lithology to define land systems (inside bioclimatic regions) and geomorphology to define land facets (inside systems). Moreover, morphometric parameters affect the ecosystems composition and distribution and therefore their functionality at different scales of analysis.

The Geodiversity indexing and mapping methods available in literature use a variety of criteria. The most used criteria are the same supporting ecological land classification: lithology, landforms, land use.

The converging objectives of assessing urban geodiversity and mapping Rome land units, opened the interdisciplinary dialogue among the authors and led to the study presented here, aiming at evaluating the heavier morphology influence on the potential biodiversity heterogeneity at a detailed scale.

For this purpose, the most used geodiversity indexes have been taken into account, in order to choose the best ones fitting our study case. We focused on methods including geomorphodiversity parameters, such as the Geomorphodiversity index by Melelli et al. (2017) modified for introducing the automatic classification of geomorphological features and tested on a multiscale analysis.

In an urban context, the morphometric analysis of topography changes, anthropogenic features and natural landforms modified by humans in time, make geomorphological mapping fundamental to calibrate the geodiversity models in a truly multidisciplinary approach to urban biodiversity investigation.

In particular, the peculiarities of the urban environment and the relative difficulties in evaluating geodiversity with methods built up and tested in natural areas, requests to consider:

• the thickness of landfill deposits characterizing anthropogenic layering in historical cities, which alters the original morphology and the local pedogenesis
• the need to define the boundaries between urban and peri-urban areas.

Besides the consolidated application in natural systems, such as protected areas, the role of geodiversity indexing and mapping is therefore promoted also in urban systems, where it can foster a truly holistic and integrated ecosystem / geosystem approach. Actually, geodiversity assessment, joined to the biodiversity one, can effectively contribute to urban green infrastructure planning by sustaining and enhancing important regulating and cultural ecosystem services.