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Urban ecosystems are cities and the surrounding, socio-ecological systems where most people live (Maes, et. al. 2016). They are very peculiar ecosystem types: they are almost completely artificial but they include, in different proportions, all other ecosystem types (forests, lakes and rivers and agricultural areas can all be part of urban fringe) and they are strongly influenced by human activities.
In the last twenty years urbanization has increased in Europe. At EU level, areas dominated by the presence of artificial land increased with 3.2% between 2000 and 2018. When considering the share of dominant land types (the proportion of areas dominated by artificial, agricultural or natural land), 69% of Functional Urban Area remained relatively stable, with no clear direction of change. When a change has occurred, it has been characterized by a loss of agricultural or natural land and an increase in areas with no clear characterization, which is a proxy of urban sprawl. Functional Urban Areas are characterized by a progressive densification of settlements. The vegetation cover of urban green infrastructure has been relatively stable in the long term, with a slight upward trend in areas of the cities that are not densely built in both core cities and commuting zones. However, when focusing on the balance between abrupt greening (defined as a relatively sharp upward trend in urban vegetation) and browning (defined as a relatively fast loss in urban vegetation), cities are not able to compensate for land taken. This means that when a loss of vegetation is observed (usually due to land use change, i.e. housing or infrastructure policies) there is no corresponding compensation strategy in place to recover the vegetation within the green infrastructure. This can result in progressive increase in fragmentation of semi-natural patches and consequential loss of city resilience. Cities and their surroundings can be part of the solution. They can host biodiversity spots and Urban Green Infrastructure (UGI) can deliver important benefits and be part of a regional eco-networks. However, defining a clear role of urban ecosystems within sectoral EU legislation and policies is required. Clear rules need to be set to compensate for land taken and vegetation loss. Moreover, there is a need for setting targets to specifically monitor urban condition, urban biodiversity and urban their ecosystem services.
Extent and change:
Europe experienced an increase of urban ecosystem type over the last 20 years with the overall area covered by urban ecosystems increasing by over 12,000 km² (or 3.4%) since 2000.
Drivers and pressures:
The total air pollutants emissions (within Functional Urban Areas) registered a reduction in the long and short term (see fact sheet 3.1.101). The result is consistent with other assessments at national level (EEA 2019a; EEA 2019b; EEA 2020). Proxies of land degradation were soil sealing and municipal waste. In both cases a degradation was registered. The share of sealed soil is significantly increasing in core cities, both in densely built areas and even more so in not-densely built areas where there are still opportunities for alternative solutions for dealing with territorial development. Municipal waste, which depends on urbanization, population density and lifestyle, is also increasing slightly in the long term. Nevertheless, the trend varies a lot among Member States, not only in terms of total amount generated but also concerning management and treatment strategies (see fact sheet 3.1.102). The analysis confirms an overall reduction in total air pollutants emissions within FUA. A more detailed analysis could consider the different sources of emissions to verify which sector is responsible for the trends. Indicators connected with urbanization present upward trends with potentially negative consequences. An example is that, the persistent increase of impervious surfaces reduces resilience of urban ecosystems and exposes them to risks presented by climatic events (flooding or heat waves).
Indicators that represent environmental quality are improving at an aggregated EU level. With regards to air pollutants concentrations, on the long term, and using aggregated average data, the situation seems to improve for the pollutants considered and the trend is consistent with other assessments which report specifically on air quality in Europe (EEA 2019b). There has been an increase in bathing locations with good water quality. The exposure to harmful levels of noise pollution derived from roads is stable for the cities where data were available and comparable. Structural ecosystem attributes, which represent the configuration of urban ecosystems, offer a slightly different picture and demonstrate a clear and intense process of urbanization in Europe. The extension of artificial areas in the long term (by 3.2%) and short term is increasing (by 2%). There is an increase in the proportion of areas dominated by artificial land type and of land with no dominant land type (zones where there is a mix of land uses). In parallel, we register a loss of areas with dominance of agricultural land or natural land. The process is confirmed by other indicators, which can be reported in more detail and for which results are statistically significant. There is a loss of areas without settlements and a relatively rapid densification of settlements within FUA.
Convergence of evidence
All air pollutants emissions marked an improvement in the short and long term (5 pollutants); municipal waste generated remained stable in the short and long term (1 indicator) and imperviousness registered a change resulting in degradation in the short term (2 indicators). No indicators, consistent with the rest of the assessment, were available for land take.In terms of condition, the concentration of all air pollutants marked an improvement in the short and long term (4 pollutants). Noise pollution from roads remained stable in the short term (1 indicator) and bathing water quality improved in the short and long term (2 indicators).
Challenges for policies on urban ecosystems fall under different categories:
-Compensation policies and biodiversity-friendly areas.
-To limit the degradation of Urban Green Infrastructure more focus should be placed on.
-Land take compensation policies. In practice, compensating for land take affects a multitude of projects (even small size ones) that “consume” agricultural and natural land.
-Management practices within Urban Green Infrastructure should carefully consider the importance of biodiversity-friendly areas.
-The role of citizens
Lifestyle and citizen engagement play a key role in the impact that population density and population dynamic (growth, structure, mobility) have on ecosystems. This is true for most topics covered in this assessment. Air pollutants emissions, concentrations and population exposure, for instance, depend (at least in part) on lifestyle choices, connected to mobility and transportation or energy use (Ballesta et al. 2006; Priddle 2018). Sustainable consumption, recycle and lifestyle affect municipal waste management and land take (Colsaet 2017; Gaudillat et al. 2018). Proper, responsible conduct is very important for biodiversity and nature conservation when enjoying nature-based recreation activities and when managing domestic gardens (Goddard et al. 2010; Nilon 2010; Beumer and Martens 2015).
A well-managed Urban Green Infrastructure is essential to support Urban Ecosystem Services such as microclimate regulation, noise reduction, flood protection, air quality regulation and nature-based recreation. The mainstreaming of Urban Ecosystem Services into urban policy making has started (many cities already have in place specific strategies on Urban Green Infrastructure) and has been promoted at EU level (EC 2019d). Nonetheless, there is a need for setting targets to specifically monitor urban condition, biodiversity and ecosystem services. The issue was discussed in October 2019, during the EU week on regions and cities , where one of the takeaway messages was that as researchers we can set up assessment frameworks but targets for monitoring urban biodiversity and ecosystem services should be set up at a local level, taking into account specific territorial context. In order to be financed and adequately implemented at a local level, NBS should be officially recognized and included in policy regulations. One of the final objectives of the Action Plan of the Partnership on Sustainable Land Use was to promote NBS as a tool to build sustainable, resilient and livable urban areas, with specific requests for a better regulation to boost NBS at European, national and local levels; and better financing for NBS.
Policies related to urban ecosystems should be structured on three levels which are complementary and not mutually exclusive:
1) Municipal level; district level a. All policies directly and indirectly linked to management and planning of green spaces and green infrastructure, mobility, waste management, water quality.
2) FUA level. The connection between urban ecosystems and the other ecosystems types should be taken into account, especially with regards to: i. croplands and the role of local agricultural production in the local market, ii. forest and its role within the Urban Green Infrastructure.
3) Regional level and National level. The regional network of cities should be considered with a view that can reflect the overall impact of urbanized areas on the ecosystems.
Cities are not “single entities” and they do not only include artificial areas. They are part of a complex largerscale, socio-ecological system. This assessment demonstrates that is very difficult and scientifically challenging to synthetize the complex dynamics of cities into a set of simple key messages or aggregated trends. However, what seems to be very important is to set up and test monitoring frameworks that help cities to identify whether their change is normal or unusual in the EU and regional context, or to provide evidence that some mayors are concerned with maintaining natural habitat in living environment of people. Functional Urban Areas, the core cities and their commuting zones, where most European citizens live and work cover 20% of the EU territory. Urban population is increasing with regional patterns that are connected to different stages of economic development. Urbanization is increasing and this is confirmed by pressure indicators (increase impact of municipal waste or sealed soil); environmental quality indicators (population density) and structural ecosystem attributes, such as the degree of densification of settlements within FUA; a decline of number of areas occupied by croplands or natural areas and the increase of areas with a mix of uses. The commuting zones are assuming characteristics similar to the core cities. When evaluating the trends in vegetation cover of Urban Green Infrastructure, we recorded a more intense loss of vegetation within commuting zones than within core cities. Pressures and environmental quality indicators that have a clear EU regulation (noise pollution, air pollutants emissions and concentrations, bathing water) are all stable or improving at EU level.