## 3 Quantification, Assessment, and 3D Visualisation of UES in Naples
### Classification of UES  
Urban Ecosystem Services have been addressed by some relevant initiatives, such as the Millennium Ecosystem Assessment [80] and The Economics of Ecosystems and Biodiversity [81]. A review of the ES approach [82; 83] has shown a wide range of ecosystem service classifications considering the typology of services and the meanings of the main terms related to \"process\", \"function\", \"service\", and \"benefits\". Some relevant classifications [11; 26; 81; 84] have defined services as those that can affect human wellbeing, either directly or indirectly. However, there are also other interpretations, which are conflicting in some cases. There is a lack of consensus related to the meaning of the term \"function\". Some authors [84; 85] have defined \"function\" as the expression of an \"ecosystem process\"; for other authors, instead, this concept relates to the capacity of ecosystems to provide goods and services [26; 86; 87], underlining an anthropocentric point of view and considering that a function becomes a service when humans enjoy it. The European Environment Agency (EEA) proposed a Common International Classification of Ecosystem Services (CICES) [88; 89] by using ES typologies refined to reflect the key emerging issues highlighted in the most recent research literature. The CICES defined an explicit hierarchical structure that includes the three familiar ES categories (Provisioning, Regulation and Maintenance, and Cultural), where the major \"Sections\" are organised into \"Divisions\", \"Groups\", and \"Classes\" [89; 90], serving as a suitable tool for integrating ES into analytical models supporting landscape and city planning. [PERSON] et al. [18] and [PERSON] and [PERSON] [19], starting from the above reflections, have underlined the role of the urban dimension, with specific attention to UES and their classification, with the purpose of providing a framework for conceptualising and managing human-environmental interactions within the broader context of sustainability [91]. Indeed, [PERSON] et al. [18] considered that UES reinforce the idea that ES can be produced in urban areas to support human wellbeing in both tangible and intangible ways, and that UES can be considered as a social tool for bringing together different stakeholders to foster community-driven and government-led planning for urban sustainability implementation [92]. According to [PERSON] et al. [17], the classification of UES considers four main types of services--Provisioning, Regulation, Supporting, and Cultural--where the term \"service\" is related to the aspects of the ecosystems used (either actively or passively) to support human wellbeing and characterised by two components identified as \"structures\" and \"processes\", expressing relationship systems in cities. In particular, structures consider the social, ecological, and technological components of cities, while processes are related to the flows of materials, energy, and information occurring between and within these components. Therefore, UES derive from the stocks and flows of natural capital, but their realisation is also connected to other forms of capital, the so-called \"human-derived capital\" [93; 94], which includes \"produced capital\", \"human capital\", \"social capital\", \"cultural capital\", and \"financial capital\" [17; 95; 96]. According to the above reflections, the classification of UES for the selected study area derives from the categorisation proposed by [PERSON] et al. [97], including the considerations of [PERSON] and [PERSON] [13], as it provides more flexibility regarding the selection of a broaderrange of functions, which are able to describe the primary services related to the urban dimension. Indeed, the UES functions have been explained by [PERSON] [87]:  
* _Regulation_, considering a group of functions related to the capacity of natural and semi-natural ecosystems to regulate essential ecological processes and life support systems through biogeochemical cycles and other biosphere processes.