Abstract
Green spaces are increasingly recognised as key elements in enhancing urban resilience as they provide several ecosystem services. Therefore, their implementation and monitoring in cities are crucial to meet sustainability targets. In this paper, we provide a methodology to compute an indicator that assesses changes in vegetation cover within Urban Green Infrastructure (UGI). Such an indicator is adopted as one of the indicators for reporting on the key area “nature and biodiversity” in the Green City Accord (GCA). In the first section, the key steps to derive the indicator are described and a script, which computes the trends in vegetation cover using Google Earth Engine (GEE), is provided. The second section describes the application of the indicator in a multi-scale, policy-orientated perspective. The analysis has been carried out in 696 European Functional Urban Areas (FUAs), considering changes in vegetation cover inside UGI between 1996 and 2018. Results were analysed for the EU and the United Kingdom. The Municipality of Padua (Italy) is used as a case study to illustrate the results at the local level. Over the last 22 years, a slight upward trend characterised the vegetation growth within UGI in European FUAs. Within core cities and densily built-upcommuting zones, the trend was stable; in non-densely built-up areas, an upward trend was recorded. Vegetation cover in UGI has been relatively stable in European cities. However, a negative balance between abrupt changes in greening and browning has been recorded, affecting most parts of European cities (75% of core cities and 77% of commuting zones in densely built-up areas). This still indicates ongoing land take with no compensation of green spaces that are lost to artificial areas. Focusing on the FUA of Padua, a downward trend was observed in 33.3% and 12.9% of UGI in densely built-up and not-densely built-up areas, respectively. Within the FUA of Padua, most municipalities are characterised by a negative balance between abrupt greening and browning, both in non-densely built-up and densely built-up areas. This approach complements traditional metrics, such as the extent of UGI or tree canopy cover, by providing a valuable measure of condition of urban ecosystems and an instrument to monitor the impact of land take.
Highlights
IntroductionUrbanisation is a complex territorial process that refers to changes in the population distribution and to a transformation of the environment (Mcgranahan and Satterthwaite 2014, United Nations 2019)
To illustrate the approach and to test its applicability in a multi-scale perspective, the model was implemented in 696 European Functional Urban Areas (FUAs), situated in the European Union (EU) and the United Kingdom (UK)
We analysed the trend of urban green areas in European cities, through a multi-scale approach
Summary
Urbanisation is a complex territorial process that refers to changes in the population distribution and to a transformation of the environment (Mcgranahan and Satterthwaite 2014, United Nations 2019). It implies changes in dominant occupations of land, lifestyle, culture and behaviour and, alters the demographic and social structure of both urban and rural areas (Montgomery et al 2004). Urban ecosystems are defined as socio-ecological systems where most people live (Maes et al 2020). The urban ecosystem includes abiotic spheres (the atmosphere, hydrosphere, lithosphere and soil or pedosphere) and biotic spheres Urban ecosystems are largely artificial but they include vegetation, green
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