5/7_GREEN SPACES AND BIODIVERSITY // ASSESSMENT CRITERIA FOR AN ECOLOGICAL URBANISM // Measurement Tools for a Mediterranean Sustainable Urban Model

When talking about sustainability a lot of people immediately picture the image of a tree… or rather a forest like the main aim to achieve. In More Than Green we try to build an understanding that sustainability is further more than some environmental actions addressed to correct an environmental issue. For this reason we talk about social, cultural, economic and environmental sustainability in the urban environment. However, this does not mean that we obviate questions related to biodiversity in our cities.

In the previous history we talked about traditional Mediterranean cities as a referent in versatility, density and therefore complexity. But not everything was so idyllic, and precisely the excess of density led into overcrowding and insalubrity in many cases. From 19th century those problems tried to be avoided, amongst other things by means of the introduction of green areas in our cities, a fact that until then was only part of the countryside beyond the city walls.

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This process led into a sponge effect in our cities, a fact that allowed the introduction of green in public spaces generating boardwalks, boulevards, parks and gardens in a process that is still ongoing. Thus, finding the better way to introduce the maximum possible amount of biodiversity in our cities is still a pending issue. This would explain why we recently find urban green not only in our streets or squares, but also in facades, roofs and other unexpected locations.

Measures like these help avoiding complete soil impermeabilisation, plus absorbing a part of urban greenhouse gas emissions. Furthermore, these questions have side-effect consequences that produce a benefit in city life. Let’s see that in today’s story that takes place in this neighborhood::

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Summertime, it is 11am and you need to go for some shopping, nevertheless sun is burning out in the streets. You live downtown and you are not in the mood for shopping at all. The sidewalks blaze and you are not going to find any shadow in your way so your decision is to stay at home with your air conditioners at the maximum performance. After a while you boot your car, turn on its air conditioner at 18 degrees and drive to the mall for shopping. As soon as you finish you return home the same way and with the same temperature. However, your friend Roberto lives in other neighborhood whose streets were remodeled a couple of years ago.

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Some ruined houses were demolished there and a square was built in its place, and now there are leafy trees and neighbors spend their evenings chatting and taking some fresh air. What is more, almost all the streets have trees and even some benches, so even Roberto is in the mood for shopping around as the streets seem fresher and nicer. But the most important point is that Roberto’s impression about his neighborhood is shared by many of his neighbors. Thus, going out even if it’s warm, does not give the impression that you are taking a walk through desert, but you are having a little day-to-day adventure.

This decision of introducing green inside our cities is sort of an answer for the problem of overcrowding that we discussed before, but not the only one… there existed another possibility: placing the city in the countryside, that is to say the Garden City. Here the presence of green would be continuous since every house would have its adjacent plot which guarantees a direct contact with nature. Well, this idyllic situation of colorful roof housing, surrounded by grass and friendly animals degenerated in the next situation:

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If you live here we recognize that you have guarantees for a higher contact with green… because your father makes sure to water the plants every afternoon, and you have the entertaining task of mowing the lawn and pruning the trees when winter comes. But all of this happens at the expense of losing touch with your neighbors, who you barely know by the way, and with the disadvantage of living so far of downtown that you don’t even think about going there by foot. (see MOBILITY article)

Out of the fence that surrounds your house you find in the middle of nowhere… no trees, no storefronts to look at, nothing. (see PUBLIC SPACE article) Is living in a house like yours the meaning of leaving close to nature for real? Perhaps it is, partially. But it is also a matter of fact that with the proliferation of houses like yours the city (or better said the non-city) has become humongous, and the former countryside is now an enormous amount of identical dwellings with some green between them. So what we could call natural, or genuine countryside, is now smaller and much further.

So now we are going to see how the introduction of higher biodiversity in our cities has implications in improving sustainability.

ENVIRONMENTAL SUSTAINABILITY. Some of these ones have already been commented, but just for emphasizing the question: it improves water self-sufficiency avoiding surface runoff; the emergence of new species in our cities increases complexity in our ecosystem, the production of food resources inside cities mitigates external demand, etcetera.

SOCIAL SUSTAINABILITY. As we said, the presence of urban green improves public space’s livability, enhancing thermal comfort, buffering the heat-island effect, absorbing environmental noise, etcetera.

CULTURAL SUSTAINABILITY. Urban green presence was anecdotic in our traditional city, at least in public space. Nevertheless the typical passive energy strategies related to vegetation that are characteristic in private edification, or what is the same, the existence of inner courtyards as natural thermal regulation elements is closely associated to our Mediterranean culture. Maybe the key is finding how to extrapolate this experience to shared use in streets, squares and gardens.

ECONOMIC SUSTAINABILITY.

Improvement of thermal comfort conditions for instance can mitigate energy demands in our cities. Thus, with a tree planting strategy in our streets we will be not only increasing urban biodiversity but also reducing our energy bill… or what is the same, obtaining multiple benefits with just an only investment.

Finally, let’s see how diverse sustainability indicators aim to measure biodiversity (or at least the possible frame for this) in our cities.

First of all, we find a couple of quantitative indicators, which translate what the “wise men” behind world organizations decide that must be the ideal for our cities with no need of an excessive explanation:

The first one measures GREEN SPACE PER INHABITANT, being estimated that in our cities the value should exceed 10 sqm of public green areas per inhabitant (as long as the goal is promoting social use of our streets and squares). We can find the reason in WHO guidelines, which set the value between 9 and 14 sqm per inhabitant. From our perspective we raise the question of whether reaching that value in the interior of our consolidated cities can impact in the loss of the necessary density and compactness to achieve the desired liveliness. Thus, this is a value we must cautiously implement. The second one measures TREE DENSITY in our streets, and estimates that our streets should have one tree every 5 meters (in this case the value fits the European standard: 200-250 trees per km of double alignment street).

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The question would be then: what is the point of having a large metropolitan park if this is so far from where I live that I am never going to go there? To counteract this usual situation in our cities (most of them surprisingly reach the previous mentioned value), the following indicator measures SIMULTANEOUS PROXIMITY TO GREEN AREAS. Obviously, different things happen in the square around the corner than in the vast green area that Tempelhof airport in Berlin has become. It depends on what you want to do you go one way or another, because size DOES matter. If you just want to go for some sun or playing an informal football match with your friends you would maybe walk to the square, but if you want to train for running half marathon (and live in Berlin) you will go to Tempelhof. The important question is having the choice to arrive to both of them easily. Thus, the indicator fixes the minimum green area surface that must be at a determined maximum distance from the population.

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The last one is called BIOTIC RATE OF SOIL and aims to measure the amount of soil in our cities that is able to host life, or what is the same, establishing a limit to asphalt, paved or built surfaces. Thus it is estimated that at least 20% of half of our cities footprint should be permeable and for this different permeability factors are assigned according to the existing surface types.

To get more technical information about these indicators you can look up pages 537-546 of Guía Metodológica para los Sistemas de Auditoría, Certificación o Acreditación de la Calidad y Sostenibilidad en el Medio Urbano.