In Spain, the green areas are included in a legal entity called reserva de suelo para espacios libres -land reserve for public open spaces-, whose total area is defined in relation to both the sector area and the sector gross floor area for building. This land reserve also includes public squares, so that the green areas are usually sharing open space with other cemented public areas.
However, these green areas are not required to be situated at a close distance from housing areas or to have a suitable shape with a certain number of tress and a well-preserved diversity of flora and fauna. What’s more, they do not need to comply any special requirement for accessibility except for the streets that head into them as it has previously been taken into account by the planning. Because of that laxness and the blindness of certain urban planners and politicians, who only see the green areas as a necessary harm to justify the legality of the urban activity and the normal urban development, our green areas are often neglected, untapped and placed in the less accessible areas of the city. Happily, more and more studies are reaffirming the benefits of the green area as an element which introduces new ecological, environmental, social, cultural, sustainable and also economic values into the cities -you can read more here: how green are our cities?-.
But the green areas, besides all the benefits provided, are also structural areas that support other necessary functions of the city. Likewise the urban infrastructures supply with drinking water, sewers, electricity or gas, a green area can also be understood as an infrastructure if it is able to provide green services to the city, exceeding its own local environment: the rivers, the urban forests and the water ponds are natural elements with a great biological and ecological interest, but also valuables as habitats in relation to the city and as areas for leisure and sports. Even more, they can hold paths and cycle lanes to connect different neighbourhoods, be carbon sinks for fixing the CO2 and the particulates in the air, form acoustic barriers against noise pollution, and become areas of water infiltration to protect the city from the floods and the storm water runoff.
Clearly, the restoration and creation of new green urban areas improves the citizens’ quality of life but, if they are only managed as single elements and not as part of a system, they can only be understood as green facilities but not as infrastructures. In other words, the green infrastructure is only completely functional if it is considered on a territorial scale that exceeds the urban settlements boundaries: in the ecosystem processes, the green areas need to be in relation to the closer green areas for strengthening both the biological and the genetic diversity of the species, the movement of flora and fauna, and the conservation and management of their habitats. At the same time, a sustainable use of the natural resources for reducing noise and pollution levels, or for managing water, wastes and productive soils, makes only sense in a territorial scale. Sustainability is only possible in a global scale that exceeds the city limits, such as the natural resources exceed themselves the city limits. Sustainability should not be read from a local but territorial point of view to understand a settlement and its environment as an indissoluble thing.
But that regional-territorial influence is maybe more intense from a social and cultural side, in which the green infrastructure can articulate the relation between the city and its territorial environment. Indeed, green infrastructures connect the urban areas to the rural land -and to the sea, forests, meadows and mountains-, insert the nature into the urban fabric, reduce the stress of the citizens, can be productive farming lands, and have symbolic and identitary values as memories of the lost nature in a transformed habitat.
In that way, the green infrastructure is something more complex than a common green space -more than an urban park, a garden or a tree-covered street- because, besides the idea of green, it provides the city with ecosystem services. The European Commission, in the Green Infrastructure report (2010), defines the potential components of a green infrastructure: protected areas, healthy ecosystems and areas of high nature values, water courses and floodplain areas, wetlands and coastal areas, meadows, forests, hedgerows and ecological farming areas, restored habitat patches, eco-bridges to asset species movement, nature friendly multifunctional zones, urban parks, green roofs and facades, and other urban areas that help minimize the climate change.
Certainly, a green infrastructure does not need to be necessarily a natural-born green area since there are only a few true natural areas or with small human impacts in Europe today. Indeed, a green infrastructe is more like a tool that develops ecological, sustainable, cultural and social functions, using local flora and fauna to integrate the city in its territorial area.
How could we develop green infrastructures in our cities? There are some significant examples, like Emerald Necklace, a system of urban parks in Boston, designed from 1878 to 1896 by Frederick Law Olmsted -who also designed New York’s Central Park- and maybe the first example of an urban green infrastructure. Other examples, like the Hamburg Green Belt, the Green Infrastructure of Chicago region, the Grey to Green initiative of Portland, the Green Strategy of Berlin, the Ontario Green Belt, the Ottawa Green Belt and the Green Infrastructure Plan for Stockholm are also interesting developments from a local to a territorial scale of the green infrastructure concept.
In Spain, the paradigm is the Vitoria-Gasteiz Green Belt, a system of interconnected periurban parks and natural spaces which contains the urban growth of Vitoria-Gasteiz by defining an area of ecological transition -an ecotone between biomes- in contact to the agricultural plain of the Llanada Alavesa and connected by water streams and ecological corridors to the inner city green areas and to the northern and southern mountains. In a territorial scale, the Green Infrastructure and Landscape Territorial Plan of Valencia and, also there, the Territorial Plan for the protection of the Huerta of Valencia, are other good examples.
Green Infrastructure report, European Commission, 2010
Infraestructura verde urbana, El blog de Fariña, 2012
The Interior Green Belt. Towards an Urban Green Infrastructure in Vitoria-Gasteiz, Centro de Estudios Ambientales, 2012
Design With Nature, Ian McHarg, Natural History Press, Garden City, New York, 1969
Land Mosaics: The Ecology of Landscapes and Regions, Richard T.T. Forman, Cambridge, 1995