Olivier Rostang is writing his Master’s thesis on Digital Green Roofs at the Swedish University of Agricultural Sciences, SLU. During an FPX talk earlier in the autumn, he told us about how to find optimal places to enhance ecosystem services in the form of green roofs by using GIS, with examples from Uppsala.We took the opportunity to ask a little more about research on ecosystem services around the world.

You have taken a closer look at other projects around green roofs and using ecosystem services in urban planning. Tell us more about this!
– There is, among other things, a large EU project that is done in collaboration with Paris, Aarhus in Denmark and Velika Gorica in Croatia, as well as with three Chinese cities, including Shanghai and Beijing. The project called ReGreen looks at how to include nature-based solutions in cities to combat urban problems. SLU participates and I had the opportunity to present my project to the researchers in Paris, something that partly complements what they do in that it brings forth the practical aspect of “how do we implement the thing we know so far?”.

– Different cities have different types of environmental problems. Paris is heavily urbanized, and there is a great risk of longer-lasting heat waves. In China there are major problems with air pollution and in other cities there may be flooding as a clearly identified risk. By collaborating on best practice in the project, it is hoped to be able to find nature-based solutions to the problems. Why? Because vegetation cools cities, actively reduces air pollution and less sealed soils allow water to permeate and prevents flooding. And the best part is that all this is low maintenance.

What conclusions can be seen from different projects in the world?
– If we take the project in Paris e.g. they have focused on generating a better understanding around if and how green roofs create environments that increase biodiversity.  They have selected around 30 green roofs in the city and done quantitative and qualitative studies on all species that exist, insects, plants, etc. They found a lot of different species and also plants that are usually found around the Mediterranean but may thrive in Paris because the city is warmer for example. If we break down the concrete information they have found so far, then 30cm seems to be the limit of the thickness of the substrate where species diversity reaches a plateau. Buildings over 12 meters high also seem less suitable for biodiversity. The roof surface also plays a role: the larger the area, the more the biological diversity decreases. This may be due to the fact that it is more difficult for species to move between roofs when the buildings are too high and that a roof surface that is too large may be too exposed to strong winds.

-An important result in recent years is the insight around balancing the efforts and not creating monocultures and building the same thing everywhere. In order to create diversity of species, one must have a diversity of infrastructure types that benefit different species.

The same can be observed in other fields. Look at projects that grow trees to bind carbon dioxide. There, it is crucial to choose several different types of trees. Previous eco-projects in, for example, Turkey, China and Brazil where only trees of one species were planted resulted in a high proportion of the trees not surviving, and yet they continue to sell these trees for carbon offset purposes and other such programs. This may be because different species interact in different ways with insects and other species, which in turn benefit other species of trees. Had they instead planted different species of trees and spread them out, they might have succeeded better.

How important is it to also look at insects and other animals when planning green areas in urban environments?
– I think it is crucial that you include that aspect, though animals often make their way to green environments regardless. In the project One Roof – Five Possibilities, the focus has been on what can be controlled, i.e. the vegetation (at least to begin with). But they have also included some aspects of helping wildlife along the way by planning beehives and old tree trunks that become habitats for insects, and they in turn attract birds. But as I said, here too diversity is an important aspect.

– What you want to achieve is as little management as possible and you can do that by using permaculture principles. An example of this is if you e.g. have a garden full of killer snails, you can see it as if you have a snail problem, or you can see it as if you have lack of duck. To regulate a certain species, you may need to reflect on which species complements it in a form of self-regulation. Because you want to achieve such low handling and need to do as little as possible.

What else is new and interesting in your field?
– I think it is remarkable that it has taken so long to understand that urban ecosystems are something you need to invest in. For example, it is important to understand the interaction between green space and health, that is, if an area becomes greener then our health seems positively affected.


“Green areas seem to be able to even out differences between health inequalities in different economic groups. ”


In Sweden, for example, there are clear health differences between different socio-economic groups. For example, groups with lower income and education are at risk of having a heart attack on average 10 years earlier than people from higher income groups, which is almost twice as likely. The basic question behind this is why people with different living conditions have different health. 

-An answer to that may be access to green areas, something we know is lacking in areas where many from a lower socio-economic group live, for example in the million programs. We know that if people with the worst health and low socio-economy are exposed to green areas, their health tends to improve, up to the same levels as the highest socio-economic groups. It can, for example, be that if you are close to green areas, it is easier to go out and walk or run. We don’t know how exactly, but we know that you will be affected by it.

-A study conducted at KTH and the Stockholm School of Economics looks at willingness to pay for green areas, generally to create a more market driven approach to integrating green It is about the residents’ interest in and appreciation of green areas in their vicinity and how much one is willing to actually pay for it.

-Another project that looks at the connection between well-being and our surrounding environment is the FPX-funded BIG project that is run at the University of Gävle.  There you map how people move in the city through different types of environments, and explore how it affects their stress level, health and well-being.

– It is a gigantic project precisely because there is so much that affects our well-being, everything from seasons and weather, to different types of people and day, urban form and so on.

Olivier points to Uppsala Municipality’s in-depth overview plan as a good example where they have taken a deep dive and put more energy into planning how to improve and develop the city from an ecosystem perspective, linked to open, collected data.

– In recent years, an absolutely incredible infrastructure of digital data has been accumulated in the world, which is largely used to advertise and sell things. It would be great if we could get better at using this data also in urban planning, for example.

We know that cities are growing faster than ever, so there is an enormous amount to contribute to projects that have not yet been planned or built. In a study published a couple of years ago in which the Stockholm Resilience Center participated, it was concluded that around 60% of all urban areas that will exist in the future have not been built yet. 

– We possess a great deal of knowledge and experience in Sweden regarding urban planning, digitalization and the use of collected data. I believe that if we invested even more in it, we could export that knowledge and show others how to plan and build sustainable and health-promoting cities.



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