Revisiting Pianosa (Italy): how the vegetation of a small Mediterranean island has changed in the last 15 years

Eugenia Siccardi ¹, Mariasole Calbi ¹, Lorenzo Lazzaro ¹, Alice Misuri ¹, Bruno Foggi ¹, Daniele Viciani ¹, Michele Mugnai ¹

University of Florence ¹

The resurvey of historical vegetation plots has become a fundamental methodology in ecological research, providing a unique opportunity to estimate vegetation and environmental change over recent decades. However, conventional techniques such as field surveys are limited in their spatial coverage and lack effectiveness in capturing vegetation change at broader geographical scales. These limitations can be compensated by using satellite data and remote sensing analysis techniques. Here, we propose an approach that integrates ground resurveys of historical data and remote sensing data to assess how vegetation dynamics are influenced by anthropogenic factors, especially land-use change and abandonment of management practices, on Pianosa, a small Mediterranean island. Pianosa island, located in the Tuscan Archipelago (Italy), hosted intense human activity in the form of an agricultural penal colony until the late 1990s when agricultural activities ceased, and the process of land abandonment began. In addition, many conservation measures have been carried out on the island in recent decades, such as the control of alien species or the eradication and restoration of natural habitats. This research aims to evaluate, in this island context, how the different vegetation types present on the island have changed in the last 15 years, both in terms of species and functional composition, and how this change can be interpreted and analysed by remote sensing analysis. The vegetation of Pianosa has been extensively described by Foggi et al (2008), who carried out several vegetation relevés, which were resurveyed in the spring of 2023. The original methodology was followed to revisit a total of 63 georeferenced vegetation plots, ensuring a strong correspondence between the location of the old and new sampling points. Taxonomic and functional turnover was assessed in terms of species and functional traits (leaf area, specific leaf area and plant height) using distance-based ordination techniques. Concurrently, the island's main land cover types were classified utilising a Random Forest model on the two orthophotos of the island closest to the initial and final sampling times. One was captured in 2007 and one in 2023. The accuracy of this categorisation was subsequently determined with an internal validation, and the percentage change in cover of the vegetation types between the 2007 and 2023 data was calculated within a buffer surrounding each plot. The preliminary results show a significant taxonomic compositional shift for all vegetation types considered. The main processes identified as responsible for such changes in species composition are: i) the spread of alien species which colonised and drastically changed the physiognomy of some contexts; ii) a significant encroachment of the grasslands by typical shrub species, with their transition to maquis; iii) a decrease of the abundance of typical rocky cliff species. Changes in the species composition of the vegetation were also identified at the functional level and through remote sensing analysis. These changes are likely attributable to alterations in the vegetation physiognomy.

Main author career stage: PhD student

Contribution type: Talk

First choice session: 2. Ecology

Second choice session: 3. Biodiversity and global change