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Top1. Introduction
In recent centuries, the changes to the environment made by mankind have become more rapid and extreme and have inevitably led to consequences in the animal and plant kingdom (Holloway et al., 1991) (Pievani, 2014). The survival of several species has been threatened and compromised. The European Union has defined an important milestone in solving this problem with the establishment of the “Natura 2000” project (Mücher et al., 2009) (Jongman et al., 2004). The “Natura 2000” project is the main tool of the European Union for the maintenance of biodiversity. It identifies animals and plants species at risk of extinction on European soil. Once the species have been selected, the project also defines how to find and delimit protected areas where different animals and plants can be monitored and cared for as they increase their units (Evans, 2012) (Ostermann, 1998). One of the essential characteristics of a candidate area is that it must coexist harmoniously with the human infrastructures already present in the area. This leads to several advantages, but it does not solve a crucial problem for some terrestrial animal species, the need to migrate. In response to this need, researchers theorized the creation of ecological corridors (Gill Jr et al., 2009) (Urban and Keitt, 2001) (Su et al., 2016) (Jongman, 1995). The ecological corridor is composed of patches defined similarly to natural areas. Their purpose is to connect distant protected areas to allow the migration of different species. Although ecological corridors are not formally regulated like protected areas, several studies (Cannas and Zoppi, 2017) propose metrics for their definition, as well as real corridors formed. The use of this technology can ideally allow species to be autonomous in their survival, but this exponentially complicates the structure and size of the territory to be monitored, making its management non-trivial. The study of the ecological corridor using complex networks allows highlighting the most critical points and to focus attention on the most fragile points. Some GIS software (Team et al., 2015) (Jenson and Domingue, 1988) already allow a study of ecological corridors. Among the most famous there are ArcGis (Scott and Janikas, 2010) and QGIS (Team et al., 2015). GIS software allows the study of geographic data through raster or vector representations of maps. It is possible to automate some operations in QGIS, which gives access to a console and a library developed in python, but these tools remain highly dependent on the logic with which the software was conceived. This paper proposes an approach for identifying, cataloging, and representing critical points in ecological corridors. The ECGraph (Fenu and Podda, 2021) open source software was developed to handle the logic of the considerations expose in this paper. Using theories of the complex networks, the goal is to provide to the user the information necessary to make a quick analysis of the structure of the corridor to quickly intervene in areas that need attention. The open source software ECOverview1 provides instead a representation of the results obtained with an interface much more minimal than GIS software, but designed to support the user in the study of ecological corridors. In the lack of multiple ecological corridors to test, the software suite will be tested on an ecological corridor resulting from a previous study. The ecological corridor is located in the metropolitan area of Cagliari, in south Sardinia, Italy. The layout of this corridor is particularly adequate for the considerations to be made on ecological corridors, due to the different territorial conformations. Also, floods that occasionally rage on the island (Bodini and Cossu, 2010) are a perfect example of natural disasters that can change the structure of the corridor.