Green infrastructure

The fragmentation of the metropolitan landscape, which is largely due to human activities, has ended or reduced ecological connectivity. This situation is apparent at 37 critical points for green connectivity. Surface run-off and floodplains have always been a key factor in urban development, and they must be assessed in order to rebuild ecological connections. Water is a scarce and very valuable commodity, and this situation is being exacerbated by climate change. From the point of view of biodiversity, the metropolitan area of Barcelona contains unusual water-related environments including the Llobregat and Besòs basins, various streams, and the wetlands and dune areas in the coastal strip.

As a result, it is necessary to examine and assess the surface hydrography as a blue structure with an ecological connection role, and the role of the region's own underground resources in ensuring the metropolitan area's water supply. The streams, rivers and permeable soils in the main recharge areas in both agricultural and forested areas, must be preserved to avoid flooding problems downstream, and in urban environments to achieve better regulation of water and heat.

Eighty per cent of the agricultural land in river valleys and mountain areas has been lost since 1956. In spite of the strong human pressure, the metropolitan area of Barcelona still has a high level of biodiversity. The same characteristics in terms of relief that determined how the land was occupied has preserved areas of high ecosystemic value in Collserola, the Garraf massif, the Ordal mountains and the Marina mountain range. These areas, which have largely retained their forest cover, are combined with agricultural activities in the metropolitan area, either in areas such as the one occupying the lower course of the River Llobregat, or those alternating with forest masses. In the Mediterranean landscape, the organisms and ecosystems in its biodiversity is under heavy pressure (afforestation, deforestation, abandonment of crop land, urbanisation), partly due to climate change. Human activity in the form of extensive agriculture and extensive livestock farming is necessary to maintain it for this reason.

The structure of the agroforestry mosaic must be restored, fertile soils protected and activities that guarantee its active management permitted, in order to prevent biodiversity being lost and to be able to guarantee the natural cycle and the supply of water and local foodstuffs, and to minimise the natural risks involved in a territory that is over-forested due to a lack of management.

The fragmentation of the territory has created transitional areas between the city and agricultural and natural spaces, which have become marginalised. In fact, 10,742 hectares of the metropolitan territory have become interstitial spaces. It is important to note that over 25% of the population lives in areas affected by some segregated infrastructure.

Meanwhile, urban planning regulations do not meet the new social demands regarding the quality and habitability of green spaces. Only 25% of green spaces classified as such actually perform an ecosystem function in practice, which means that the areas allocated to green spaces by planning are an imprecise, non-permeable and not particularly green system. In fact, 65% of the population live in urban environments suffering from a high impact from motor vehicle traffic and with few urban green areas.

This means that urban settlements must be reconnected with the environment, the quality of green spaces must permeate into the fabrics, with a focus on their relationship with the natural and productive environment. Green connections and parks with metropolitan value, which make cities socially and ecologically cohesive, are particularly important in this relationship.