Biogeography of urban green spaces: direct and indirect drivers of biodiversity and ecosystem services in Rome (UrBiS)
Descrizione
The last century has witnessed a massive human influx to urban areas, resulting in an extensive urban encroachment worldwide. More and more biodiversity is being embedded in an urban matrix, therefore requiring careful planning and management. Urban green spaces can host considerable amounts of biodiversity and make important contributions to biodiversity conservation, and provide several ecosystem services to citizens. It is therefore fundamental to understand the mechanisms that support biodiversity and related services in urban contexts to define good planning and management practice. Urban ecosystems generally differ from surrounding ecosystems both in structure and composition. Factors such as patch area, isolation and shape, microclimate, and the many forms of anthropogenic factors, can all exert an ecological filter favouring species with specific traits, and increase opportunities for the establishment and expansion of alien species. The different resulting species assemblages often result in altered species relative densities due to ecological release effects, and different overall diversity. While each of these biodiversity drivers has received some attention in some taxa, their effect has been assessed mostly in isolation, therefore mostly ignoring how the effect of certain drivers is mediated through effects on other groups. Further, while drivers of ecosystem services in urban areas have been studied, little has been done on exploring the synergies and conflicts with biodiversity conservation goals. Here we propose to estimate the role of multiple drivers of urban biodiversity and ecosystem services in a more holistic framework, and assess the interlinkages between the biodiversity patterns of different taxonomic groups and their synergies and conflicts with the ecosystem services provided. We focus on the metropolitan area of Rome, the largest city in Italy and one of the largest and greenest in Europe. We will select a representative set of green spaces, and conduct an intense seasonal sampling of different taxonomic groups (herbaceous plants, insects, bats and birds) to estimate species’ relative abundance and derive species and functional diversity indices. Since native and non-native species are expected to respond differently to different drivers, their patterns and drivers of diversity will also be explored separately. We will model the effect of the multiple drivers on the diversity of the different groups, their interlinkages, and related ecosystem services using structural equation modelling. This project will contribute to unravelling the mechanisms supporting biodiversity and ecosystem services in urban areas, as well as shedding light on the synergies and trade-offs between biodiversity conservation and ecosystem service provisioning. The results of this project will therefore help delineate best planning and management practices for citizens’ well-being, ecosystem service provision, and biodiversity conservation.
Finalità
Unraveling the drivers of biodiversity and ecosystem services in urban green spaces of Rome, disentangling direct and indirect effects and assessing the interlinkages of different taxonomic groups (plants, bats, birds and a selection of insect taxa). Specific objectives are:
- Quantify biodiversity patterns (alpha and beta, species and functional) and estimate their drivers of spatial variation in four taxonomic groups (plants, bats, birds and a selection of insect taxa)
- Disentangle direct from indirect effects of biodiversity drivers while accounting for the causal effects among the diversity of different taxonomic groups
- Estimate how the effect of biodiversity drivers varies between native and non-native species
- Estimate how (regulating and non-material) ecosystem services associated with urban biodiversity vary with spatial configuration, microclimate, anthropogenic disturbance, and their synergies and conflicts with biodiversity
Risultati attesi
Task 1.1 Compiling geospatial dataset
Task 1.2 Characterising urban green spaces
Task 1.3 Selection of study sites
Task 2.1 Biodiversity sampling
Task 2.2 Covariates recording
Task 2.3 Trait data collection
Task 3.1 Diversity estimates
Task 3.2 Exploring biodiversity drivers and patterns
Task 3.3 Patterns of non-native species
Task 4.1 Quantification of ecosystem services
Task 4.2. Quantifying synergies and conflicts between biodiversity and ecosystem services
Stato dell’arte
The last century has witnessed a massive human influx to urban areas, resulting in an extensive urban encroachment worldwide and more and more biodiversity being embedded in an urban matrix. Ecosystems can be deeply altered once fragmented and surrounded by an urban habitat, jeopardising long-term species persistence and ecosystem functioning; however, urban areas can also present opportunities for biodiversity conservation and help reach the targets of the post-2020 global framework for biodiversity. Studies have indeed revealed that urban green spaces can host considerable amounts of biodiversity including species of conservation concern and provide important ecosystem services to. A good understanding of biodiversity and ecosystem drivers in urban areas is therefore pivotal for ensuring a sustainable future. Biodiversity in urban green spaces generally differs in composition and structure from the surrounding. Factors such as patch area, isolation and shape (i.e. island dynamics) microclimate (i.e. heat island effect), and the many facets of anthropogenic influence (supplemental resources, direct and indirect disturbance, active management, etc.) and their interactions can all exert an ecological filter on species favouring those with pre-adapted traits. Further, urban contexts often prove beneficial for the establishment and expansion of alien species. The altered species composition, especially due to the absence of large-bodied and large-area requirement species that are generally at the top of the trophic chain, generally leads to an impoverishment of the trophic web and ecological release effects, that coupled with the availability of resources of human origin, may result in the over-abundance of some species. Examples include pest species that thrive in urban contexts damaging ornamental and natural plants due to the absence/rarity of natural predators and parasitoids. Overall, this results in novel species and functional patterns of biodiversity along gradients of green areas’ size and configuration, and edge-to-core and periphery to city-centre gradients, and gradients of anthropogenic disturbance. Alien species diversity may follow similar patterns as natives in response to resource gradients or alternatively, since alien species typically respond differently to biogeographic drivers [e.g. isolation] and anthropogenic disturbance, the diversity of these two groups of species may not covary within cities. While many studies have investigated the role of spatial configuration, microclimate and different disturbance factors on biodiversity, their effect has been assessed mostly in isolation and for individual taxonomic groups separately. The diversity of a taxonomic group can also strongly depend on the availability and diversity of its trophic resources as well as on interactions with other taxonomic groups, creating causal dependencies between diversity of different taxonomic groups. For example, invertebrate diversity may mostly depend on plant diversity, which in turn can be mostly related to patch area; insectivorous birds and bats are often specialists of insects of different sizes and mode of life, so insect functional diversity can be the primary driver of insectivore vertebrate diversity. Investigating the effect of seemingly direct drivers on individual taxa may therefore conflate direct vs. indirect effects, undermining our understanding of the implications of different urban planning strategies. Understanding the interrelation between different groups and cascading effects therein, can provide fundamental insights for a more scientifically-underpinned urban management and planning to maximise biodiversity while limiting the expansion and over-abundance of alien and harmful species. Numerous studies have documented important positive physical, psychological and cultural effects of urban biodiversity on people. Ecosystem services of urban biodiversity include increase in air quality through filtering, microclimate regulation, and reduction of noise level. It also provides important health and psychological effects, as well as recreational opportunities. However, the maximisation of such services does not necessarily correlate with biodiversity levels and biodiversity conservation. For example, human accessibility to green space increases psychological and health benefits, but results in smaller and more fragmented areas, with supposedly lower biodiversity levels. It is therefore fundamental to understand the mechanisms that support biodiversity in urban contexts, and how they relate with biodiversity levels, to define good planning and management practice that takes into account both biodiversity and ecosystem services.
Riferimento: PRIN 2022 – Codice progetto: 2022Y7MY32 – CUP: F53D23004180006
Investimento totale del progetto: 231.458,10 €
Partner/proponente: Università degli Studi di ROMA “La Sapienza”(Coordinatore), Università degli Studi Roma Tre, Consiglio Nazionale delle Ricerche
Coordinatore dell’UdR Università degli Studi Roma Tre: Marta Carboni
