Connectivity of green and blue infrastructures: living veins for biodiverse and healthy cities

What is green and blue infrastructure?

BIOVEINS focuses on the role of green and blue urban infrastructure on biodiversity. What is it?

Grey infrastructure refers to buildings, roads, and other urban constructions. Blue infrastructure refers to water elements, like rivers, canals, ponds, wetlands, floodplains, water treatment facilities, etc. Green infrastructure refers to trees, lawns, hedgerows, parks, fields, forests, etc. These terms come from urban planning and land-use planning.

In the past, roads and settlements seemed like human habitats that helped us to move across the landscape and find safe places to live in the wilderness. Today, there is so much "grey" infrastructure, in cities and in rural areas, that we are in the opposite situation. Land planners now talk about forming stepping stones and networks of blue and green infrastructures to allow animals, plants, water, clean air, and so on, to move safely around the landscape.

Europe has a large number of relatively small cities distributed somewhat evenly, with only two megacities: London and Paris. Across Europe there are different patterns, but many countries have a relatively high population density across large areas of the country, with an increasing trend towards medium-density peri-urban and suburban residence. Only central Spain and the Scandinavian countries have large areas of rural "wilderness". In 2016, the average population density in Europe was 16.4 inhabitants per km2, but this doesn't tell us much since only 44% of the total area of Europe is inhabited. Perhaps a better way to imagine the distribution of urban areas is that just 10% of Europe's area contains 75% of the population: in these areas, the population density is about 2400 inhabitants per km2. In the images above, you can see where people live in Europe-- and where people live, there is "grey infrastructure".

In the second image, you can compare the Berlin metropolitan area to a zoomed-out larger area with a more suburban-urban distribution of inhabitation. You can observe how the fragmentation and mixing together of green, blue, and grey infrastructures is much lower in the large city. These maps are from Eurostat, and you can find more statistics about urban life here: Eurostat Urban Europe 2016

Blue-Green Infrastructure can also specifically refer to an urban planning approach in which design of naturalistic or completely artificial infrastructures in the city is intended to allow the whole water cycle to occur within the city. This can improve the delivery of water-related ecosystem services (reducing pollution in the air, irrigating parks, providing local drinking water), as well as preventing harms like flooding and spread of contaminants (e.g. from cars). These designed infrastructures include things like "bioretention cells" also known as "rain gardens", which are small, specially constructed gardens where runoff from rain collects and contaminants and sediments are filtered out into the soil; "bioswales" or depressions where water runs slowly and contaminants and sediments collect and are filtered out into the soil or other structural material; water reservoirs; restored rivers with wet meadows where they can meander (curve naturally); wetlands constructed for bioremediation, by collecting contaminants in the tissues of the reeds; urban trees; small urban parks; green roofs and green walls. We will discuss some of these designs later in this blog.

--Meredith Root-Bernstein