Greening the City

Redesigning cities

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Ville et biodiversitÚ

Green-blue networks for cities

In France, the recent Grenelle Environment Forum made the creation of urban green networks one of its top priorities.  The goal is to protect against the loss of biodiversity caused by the expansion of built-up areas that break up natural habitats. The idea is to link natural habitats together, enabling animals and plants to move along ecological corridors connected to the city's surroundings. Green grids of this kind can be based on existing links, such as tree-lined avenues, railway lines, embankments, vacant lots, wasteland, etc. Cyclists and walkers can also benefit if footpaths and cycle paths are included. Blue networks, consisting of planted watercourses and bodies of water, could complete the network.

But how can such networks be made effective, so that the various species present in cities actually make use of them? What type of vegetation should be planted? What about the impact of lighting and noise? What ecological services could they provide? Is there a risk that they will promote the presence of species that are undesirable or that carry diseases transmissible to humans? How can such networks fit into city planning programs?  To such questions scientists still have very few answers. Hence the importance of the French 'Urban Green Network' research program (1) launched in 2009 and involving eleven research groups in the life sciences and social sciences in seven cities. Results are expected in 2012.

However, several cities throughout the world have already begun to apply the concept. For instance, Nantes is making use of the many waterways that criss-cross the city. Brussels has plans for a green grid that will link up the Belgian capital's parks. In Curitiba, Brazil, an ecological corridor dubbed 'green line' will connect neighborhoods which until now were separated by a highway. And Barcelona is aiming to set up a green corridor in the city center.

1. Program funded by the French National Research Agency with the participation of CNRS.

CNRS    sagascience