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Drones and predictive mathematical models to preserve the "Cargola del Cap de Creus"

The "Cargola del Cap de Creus" (Erodium foetidum (L.) El Hér.) is a small endemic plant, considered endangered, which is only located between Montpellier and Perpignan, in France, and the Cap de Creus, where the only known population of the Iberian Peninsula survives in isolation.

In an attempt to prevent their extinction, the Catalan Society of Sciences for the Conservation of Biodiversity (BioSciCat) has started a project focused on their study and conservation. The research will focus on figuring out demographic, biological and ecological aspects, essential knowledge for designing the future "Recovery Plan" for the species.

The reduced population numbers of E. foetidum are one of the reasons for which it is placed on the edge of extinction. For this reason, dismissing or confirming the existence of new locations that increase the genetic and ecological resilience of the species has been one of the key aims of this research project.

Since the only known Iberian population is confined to Cap Norfeu, a small peninsula located in the south of Cap de Creus (Girona), it has been of great interest to survey this territory and its area of influence to get the maximum information and thus be able to accurately determine its state of vulnerability.

The field campaigns to progress in the knowledge of the biology and demography of this plant began in February and have lasted until mid-September. Throughout these, BioSciCat has relied on the application of innovative techniques to get the highest information.

In order to find out if Cap Norfeu is the only place in Cap de Creus where Erodium foetidum grows, a predictive mathematical model has been developed based on topographical, climatological, geological and ecological variables to determine the probability that the species could grow in other areas of the Natural Park. The areas that the model has identified as having the highest probability of hosting populations of the 'Cargola del Cap de Creus' (those with the highest ecological suitability for the species) have been visited but, in none of them, have been found. Thus, the hypothesis that the Cap Norfeu population constitutes an isolated redoubt from the rest of the populations in the south of France is reinforced, with which it probably keeps a very low or null genetic exchange. However, in the area of Cap Norfeu, the explorations guided by the model have allowed the discovery of three new localities that gather more than three hundred individuals.

On the other hand, in order to have a census of the number of individuals as accurate as possible, in addition to carrying out counts on the ground, the calcareous cliffs facing north, where part of the population resides, have been scrutinized with the help of a drone equipped with very high resolution camera (4k). These individuals cannot be observed directly and the use of binoculars is not always possible due to the difficult accessibility of the land.

It now remains to analyze the huge collection of data obtained in order to transform all the effort invested into results and conclusions about one of the most threatened plants in our geography, which could contribute to its conservation.

The 'Cargola del Cap de Creus' research project is part of BioSciCat's "Unique" program, a line of action aimed at promoting the conservation of the most threatened living beings, the worldwide distribution of which is delivered to our territory. It has, among others, the support of the Fundación Biodiversidad, the Ministry for the Ecological Transition and the Demographic Challenge, and the Department of Territory and Sustainability of the Generalitat of Catalonia and the collaboration of the Cap de Creus Natural Park.



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