Phd in ENVIRONMENTAL AND EVOLUTIONARY BIOLOGY

Thesis title: Analyses of environmental factors affecting Potential Natural Vegetation in different types of urban ecosystems: a tool for supporting effective forestation

Urbanisation represents one of the most transformative forces shaping contemporary ecosystems, with important impacts on biodiversity and ecological processes. Ongoing urbanisation trends are expected to worldwide affect the sustainability and resilience of ecosystems in terms of biodiversity, ecosystem services, and human well-being, as citizens are often exposed to environmental conditions detrimental to their health. In Europe, the Nature Restoration Regulation (1991/2024) emphasises the role of cities in biodiversity recovery, given that urban areas cover 22% of the EU’s land and host most of its population. Key measures include achieving No Net Loss of urban green spaces (e.g., parks, green roofs, urban forests) and tree canopy cover by 2030, as compared to 2024 levels, and their increase from 2031 onward until satisfactory levels are met. Ground-based knowledge of urban ecosystems at the local level is essential for implementing restoration actions, including Nature-based Solutions (NbS) and Green Infrastructure (GI), to support and conserve local biodiversity in cities. Within the framework of the National Biodiversity Future Center (Spoke 5 - Urban Biodiversity), this research aimed at developing an integrated framework to define and map Potential Natural Vegetation (PNV) as a knowledge tool viable in urban and peri-urban landscapes, by combining new methodological insights with field observations. Through three interconnected research activities conducted in the Italian Functional Urban Areas of Rome and Campobasso, this work provided a holistic understanding of how anthropogenic pressures can alter vegetation dynamics while proposing actionable solutions for sustainable urban planning. The research builds upon a hierarchical methodology for PNV mapping (first research topic), which integrates bioclimatic, lithological, and geomorphological spatial analyses with phytosociological surveys. By employing multivariate analyses to identify diagnostic environmental thresholds, this approach produced high-resolution ecological maps that improved existing regional and national cartographic products in both precision and thematic detail. This methodological advancement is not only able to properly support ecological restoration, by providing reference models, but also serves as a critical baseline for detecting anthropogenic impacts on vegetation systems, especially when other variables typical of highly urbanised areas are considered. Focusing on these impacts, the second research topic was directed towards the understanding of how the urban landscape may disrupt PNV character and mature successional stages, with a focus on anthropogenic landform modifications impacts in the case study of Rome. Through comparative vegetation analyses across a disturbance gradient, the study revealed that anthropogenic landforms caused a shift in woodland composition, favouring invasive and nitrophilous species while altering edaphic and microclimatic conditions. These findings demonstrated that urban forests comprise distinct floristic assemblages, necessitating revised frameworks that also recognise the environmental and dynamic profile of novel ecosystems. Differences in species composition between woodlands in different conditions were thus quantified, in terms of ecological distances from PNV, modelled and mapped across the city. The identification and spatialisation of areas that shifted furthest from reference systems, with an unlikely reversible deviation from PNV, represent a useful finding for the practical implementation of the research. Moving towards the urban - periurban interface, the third research topic examined how landscape fragmentation and edge effects facilitate biological invasions in transitional shrubland ecosystems. Combining field surveys with landscape metrics analysis, the research quantified invasion drivers and developed a predictive model of invasibility. Based on these ecological insights and the availability of PNV maps, the study also proposed a practical solution through the design of a targeted GI network that simultaneously addresses invasion containment and habitat restoration—a model adaptable to other peri-urban regions. This work achieved three key contributions: (1) a standardised yet flexible protocol for PNV typification and mapping in urban ecosystems; (2) empirical evidence of urbanisation's cascading effects on environmental characters, landscape mosaics, vegetation systems and dynamics; (3) science-based strategies for managing novel urban ecosystems and integrating PNV knowledge into spatial planning processes. Management and planning tools were therefore provided to reconcile urban ecosystems with biodiversity conservation and restoration, particularly relevant for Mediterranean regions and other global biodiversity hotspots undergoing rapid urbanisation. The integrated approach developed here provides a template for addressing one of the critical challenges of actual time: designing cities that behave as self-sustaining socio-ecological systems. Future applications could extend this framework to other biogeographical contexts, incorporating additional dimensions such as climate change resilience and ecosystem service optimisation.