Most of us probably appreciate green roofs as a clever adaptation action that has not just many additional benefits but can be simply nice. We know inspiring examples from Basel, Malmö, Copenhagen, Rotterdam, Frankfurt and many other cities. So I was wondering, when I flew in to Valencia at the beginning of summer and saw all the empty flat roof tops: What a wasted potential!
The next morning I walked from my hotel to the meeting venue and enjoyed the fresh air of the huge park of the City of Science and Arts in the heart of Valencia. What a relief from heat! However, I was wondering where the water for these very green loans would come from during these hot summers in the Mediterranean. Indeed, when I asked my Spanish colleagues a bit later they confirmed to me that the supply is somehow challenging. Actually, they use non-potable water as Valencia has a double network that delivers also water of lower quality for other purposes. This sounds good, but still this water comes also from the aquifer and its abstraction stresses fresh water resources.
I came into thinking. Is our almost unquestioned paradigm here in the middle and more northern parts of Europe that green roof do good is universally right? I imagine that it could be a
challenge to provide all the water for the vegetation to grow on the roof tops in the heat and dryness of the Mediterranean summer. If the green roof is just meant for insulating the buildings,
normal building insulation and white roofs might do the job much cheaper. Or is it a nice space for people? I am not sure, at least not on the high rising, buildings. Could that be enjoyable in
the heat? I am not the green roof expert and maybe there are good and sustainable examples also in a hot and arid climate. I would love to hear more from such examples.
We need to rethink our approach
This experience makes me also wonder, if we that live further up in the north could learn from the south? We experience a very hot and dry summer up to Scandinavia over a long time. Also in my
region, all loans are burnt, shrubs and trees suffer. The city of Frankfurt puts huge efforts in watering the public trees and asks its citizens for help. However, in the region, where the
Frankfurt water is sourced, municipalities experience extreme scarcity themselves. Angry citizens ask how Frankfurt could water trees while they themselves need delivery by tank now. We need
rethink our strategies to manage our green areas in cities under the future climate. Recycled grey water from households and industries might be a source; harvesting rainwater in wet periods at
large-scale another one. And did I just say: ‘all is burnt’? Not exactly. There are some plants in the loans that did better. Actually, they are considered as ill-reputed as weeds, but maybe they
are part of our future solution?