Titolo della tesi: Mountain biodiversity and global change: global to local perspectives
Human pressures such as land-use changes, pollution, and greenhouse gas emissions are the main drivers of global climate and environmental changes. Climate change impacts nearly every biological and ecological process on Earth, from genetic diversity and species physiology to population dynamics, community structures, and ecosystem functioning. Together with climate change, land-use change ranks as the most significant driver of biodiversity loss and ecosystem decline.
Mountain ecosystems, though covering less than 20% of Earth's surface, play an essential role in supporting biodiversity and providing essential services such as water and energy. These regions support one-third of the world's terrestrial species diversity and host half of the 34 global biodiversity hotspots. Mountains have served as refugia for organisms during past climate changes and are expected to do the same under future climatic shifts. However, mountain species are particularly vulnerable to climate change due to their high degree of specialization to narrow tolerance bands of environmental conditions, which often restrict them to restricted elevational ranges. As temperatures rise, many species are being forced to move to higher elevations, resulting in shrinking ranges and an increased risk of extinction. Protected areas (PAs) are essential to protect species from human pressure, but isolated areas might not be sufficient to ensure the conservation of wide-ranging species, which require connected habitats to maintain viable populations, highlighting the need for ecological corridors. In this context, local-scale studies are critical to understanding the specific dynamics of ecosystems and to develop tailored conservation strategies, particularly in hyper-diverse and vulnerable regions like mountains.
The overarching goal of this PhD project is to analyse the impacts of global change drivers—such as climate change, land-use change, and human population density—on mountain ecosystems. There are five specific objectives: 1) assessing the exposure of mountain areas to global change, 2) predicting future change in the realised climatic niche of mountain carnivores and ungulates, 3) predicting future shifts in mountain species distribution under different emission scenarios, 4) untangling the role of Marsican bear corridors in supporting the populations of other mammals, 5) mapping the local-scale density of grazing livestock in Central Apennines. Each objective has been developed into a research Chapter.
The project emphasizes the importance of integrating both global and local perspectives to create effective conservation strategies for mountain environments. My research assessed the risks faced by mountain species by calculating their exposure to global change drivers and their biological capacity to cope with these changes, that is their sensitivity. I then included a local-scale component, examining the role of unprotected areas adjacent to PAs in supporting wildlife populations, and how these interact with local human pressures, such as grazing. The knowledge produced as part of this PhD is discussed in the context of international conservation policies, and how these translate into practical, on-the-ground, actions.
To understand the survival dynamics of mountain species under global changes, it is essential to examine both their exposure and sensitivity. Exposure refers to the degree to which a species or ecosystem is subjected to climate variations over time, while sensitivity indicates a species' ability to cope with these changes.
In my first research Chapter, I quantified the exposure of mountain ecosystems to three key drivers—climate change, land-use change, and human population density—by analyzing two spatial-temporal metrics: velocity and magnitude of change. I found Africa’s tropical mountains facing the highest future exposure to multiple drivers of change. Conversely, European and North America’s mountains experienced more limited exposure to global change and could act as local refugia for biodiversity.
To assess species sensitivity, the other key element of climate risk, in my second research Chapter I focused on niche breadth, which is a measure of the range of environmental conditions a species can tolerate. A reduction in niche breadth—or a shift in this range—can limit a species' ability to adapt to new conditions, making them more vulnerable to extinction. I investigated how alternative emission scenarios may determine change in the realized climatic niche of mountain carnivores and ungulates in 2050. I based my predictions of future change in species niches based on how species have responded to past environmental changes, focusing on the probabilities of niche shrink and niche stability. I found that achieving the Paris Agreement’s commitments would substantially reduce climate instability for mountain species, reducing the probability of niche shrinkage by 4% compared with a high-emission scenario.
In my third research Chapter, Using Species Distribution Models (SDMs), I then projected the future distribution of 33 mountain mammal species and 345 non-migratory mountain bird species under different emission scenarios, including SSP-RCP 1-2.6 (low-emissions scenario) and SSP-RCP 5-8.5 (high-emissions scenario). I incorporated topography and climate in the model and applied a land-use filter on the projections. I then assessed the impacts of global change on species' ranges across mountain regions worldwide, accounting for realistic dispersal scenarios. My findings show that under a high-emissions scenario, species are expected to experience significantly greater range loss compared to the low-emissions scenario (16.59% for birds and 14.98% for mammals more).
As a general outcome of the first three global-scale research Chapters I found species in tropical mountain ranges, particularly in Africa, Central and South America, and Oceania, faced the highest risks of range loss due to their high exposure to climate and land-use changes. In contrast, temperate mountain regions in Europe and North America showed lower exposure and housed species that were more resilient to global changes. This suggests that these temperate mountain regions may serve as future refugia for biodiversity, and conservation efforts should prioritize protecting these areas to mitigate the impacts of climate change.
However, while PAs are crucial for preventing species extinction, they often face local challenges such as insufficient funding and human pressures. Furthermore, wide-ranging species require connected habitats, and the 2030 EU Biodiversity Strategy emphasizes expanding protected areas and integrating ecological corridors to link isolated PAs. Therefore, in my fourth research Chapter I focused on two ecological corridors designed to enhance habitat connectivity for the critically endangered Marsican brown bear (Ursus arctos marsicanus) in the Central Italian Apennines. Using data from camera traps, I assessed the population densities of eight mammal species within these corridors. The results showed high densities for several species, particularly ungulates. This highlights the importance of these corridors not only for the Marsican bear but for a broader range of species that depend on connected habitats for survival. To ensure the long-term survival of both the Marsican bear and its coexisting species, an effective management of these corridors, with a focus on reducing human disturbance and improving connectivity, will be essential. This requires a thorough understanding of the impacts of human activities, such as livestock farming, on ecological dynamics.
Livestock grazing can significantly influence vegetation structure, nutrient cycling, and wildlife behavior. However, standardized methods for estimating grazing pressure are often lacking. To address this gap, in my fifth research Chapter I developed a protocol for mapping livestock density in the Central Apennines. This protocol combines municipal grazing data, interviews, and geospatial mapping to create fine-scale distribution maps for cattle, sheep, goats, and horses. By quantifying grazing pressure, this framework provides critical insights into livestock-wildlife interactions and informs more effective ecosystem management strategies.
My PhD thesis highlights the complexity of risks faced by mountain biodiversity due to global changes, calling for a stronger focus on long-term monitoring, adaptive management, and ecosystem restoration in high-risk areas, such as tropical mountains, and underscores the role of temperate mountain regions as potential climate refugia for species. My findings make a key contribution to Target 3 of the Kunming-Montreal Global Biodiversity Framework, which aims to protect at least 30% of terrestrial and inland water areas by 2030, focusing on regions critical for biodiversity and ecosystem services, such as mountain refugia. My research reinforces the Framework’s goal to maintain ecosystem integrity, connectivity, and resilience, specifically advancing Goal A. Additionally, my research emphasizes the need for an integrated approach that aligns global objectives with localized studies, such as those I conducted in the Apennines. With the local-scale research Chapters, this thesis also supports the European Biodiversity Strategy, particularly Pillar I, which emphasizes expanding, reconnecting, and effectively managing protected areas to establish a coherent Trans-European Nature Network.