sUsanne Hablützel stared at the rooftop garden windows, breaking her workday. The view is not spectacular: a pile of dead wood sits on a tidy plot that houses Cocory, Toadflax, Thistle and Moss.
But Hablützel, a biologist who was in charge of Basel’s natural project, was fascinated by the plants and creatures brought by the roof. You can also see birds now–that was not the case before. ”
Hidden above the streets of Basel is an unstriking environmental wonder: Thousands of gardens perch on otherwise unused roofs. Thanks to policies enacted decades ago, the city has some of Europe’s greenest roofs – an average of more than 5 square meters (50 square feet) per person in 2019, or about the size of a large balcony.
The roof ranges from buildings on small office buildings (such as those in which Hablützel spy blackbirds stuff worms into their beaks to vast open spaces covering shopping malls, warehouses and hospitals. What makes Basel stand out among many other cities with green roofs is its insistence on using local seeds and plants — rather than treating green roofs as boxed exercises.
“Basel’s green roofs are like industrial wastelands, and their wildflowers are very good,” said Dusty Gedge, president of the European Federation of Green Roofs and Walls. He described Basel’s roof as a brown spot closer to the dry and natural grassland than the monotonous green grassland.
“Now, you show this to most people, and they go: ‘I don’t want to be on the roof.’” Gedge said. “But that’s what it provides for biodiversity.”
Basel’s attempts toward green roofs began in the early 1990s, when residents voted in favor of putting their bills into funding energy-saving measures. A green roof is the solution. Although this is not the first city to reach this concept – Linz, Austria and Stuttgart, Germany, began to promote them in the 1980s and have impressive coverage today – Basel quickly strengthened its plans by forcing green roofs on all new and renovated buildings with a slope of less than 10 degrees.
“This is the secret to success,” Habzel said. “It’s not only legal requirements, but also support subsidies, and the back and forth between scientists and cities.”
The most famous of these experts is Stephan Brenneisen, who leads the Urban Ecology Research Group at the University of Applied Sciences in Zurich. He made an academic introduction on the green roof 30 years ago, attracting the interest of the Basel authorities, and since then he continues to develop guidelines on how to design the city’s green roof.
“When we started, we did make them really basic,” Brennisson said. “But we found that it was very difficult and complex for companies that did this because this topsoil wasn’t easy to deal with.”
Brenneisen has since worked with the city to set standards for the depth of the garden and the types of seeds available. This is a fine-tuning exercise. For example, as climate rupture puts Basel in the face of violent weather exposure, the city’s minimum thickness increased from 12 cm (5 inches) to 15 cm.
Nevertheless, fundamentals have not changed over the past three decades, Brennisson said. “What I learned is that it’s a simple technique.”
Supporters praised the green roof as an inexpensive tool that is short in space and can be used to create natural oasis in urban areas. Like a park, the green roof cools the air during heat waves and stores water in storms. They also protect citizens from noise, reduce air pollution, and provide shelter for wildlife that people can also enjoy.
However, without policies supporting the prices of green roofs or social welfare, real estate developers will postpone them due to the cost of building them – owners blocked by maintenance costs. Depending on their size, the extra weight may also mean more concrete and steel is used in the building, thereby increasing the building’s carbon footprint.
After the newsletter promotion
“It’s an argument that Excel files are very good at arguing,” Gage said. “A green roof does a lot of midhole things… a solar panel or air conditioning unit can benefit one benefit. What we need is something that offers a variety of benefits. A green roof is a few things.”
So far, green roofs have barely hindered the rebound or lobbying of other environmentally friendly building solutions such as heat pumps, but there is still conflict. When cities like Basel first started building green roofs, they took advantage of unnecessary space. But the renewable energy boom has made developers and building owners increasingly cover roofs with solar panels instead of factories.
“PV panels pay directly for themselves, so they make a profit for everyone,” said Rebecca Landwehr of the German Building Greening Association. “It’s difficult when there’s so much competition for roof space.”
Some cities are trying to address tensions between climate change and adapting to their impacts by pairing green roofs with raised solar panels. Panels cover plants and protect them from wind, while plants cool the panels, thus improving their efficiency. Hamburg will build a “sun-green roof” in new buildings and renovations since 2027.
The industry says the bigger obstacle to green roofs is persuading city planners to update their building regulations.
“In fact, it’s not easy to change cities,” Brennisson said, adding that most cities rely on information activities and subsidies, but no longer make it necessary.
He added that thirty years ago, Austrian traffic planners told him that people like to make brochures on green plans – but if they don’t go further, it’s just a bad thing Billy. “After a certain point, you have to make it mandatory.”
