Frankfurt: Heat pioneer in green

In the hot summers of 2018 and 2019, Frankfurt am Main recorded the highest average annual temperatures in Germany. As Germany’s fifth-largest city, it also faces the challenge of urbanization. This is known to be at the expense of green spaces. The city is still well served by this – half of the areas are green or blue and there are around 200,000 trees. However, its location in the Rhine-Main basin means that there is little air exchange. So how is Frankfurt responding to heating as a result of climate change?

Frankfurt recognizes the important role of green and blue in stabilizing the city’s climate. “Adapting to climate change is the central task of future and public services in Frankfurt,“ says Rosemarie Heilig, Head of Climate and Environment. The city is adapting the available resources so that climate-adapted measures can be transferredasquickly as possible from a city-wide to a local level.

On the one hand, this requires a sound data basis. This is why Frankfurt prepares expert reports,modelsand simulations. For example, the “Climate Plan Atlas” summarizes knowledge about the urban climate in a comprehensible map format and serves as a basis for assessment. Here, Frankfurt’s heat hotspots are clearly recognizable: wherever high solar radiation, low air exchange and a lack of green spaces come together. These are mainly the banking district, industrial parks and some residential areas. In contrast, the green belt, the Main green space, the rivers and the winds from the southwest and northeast provide cooling. On the other hand, Frankfurt is pursuing a “double inner development“: the further development of built-up inner areas while at the same time increasing the quality of open spaces. The city pooled its expertise back in 2008 in the inter-agency“Climate Change Coordination Group”. This resulted in the “Frankfurt Climate Change Adaptation Strategy 2.0”.

Since 2022, Frankfurt has also been part of the “Globally Sustainable Municipality of Hesse” program. Based on the seventeen sustainability goals of Agenda 2030, the city is developing a strategy that will have an impact at municipal level and improve the quality of life of its citizens. To this end, “Frankfurt Green City” is analyzing existing sustainability activities and summarizing the results in a sustainability report. On this basis, the city then develops a concrete sustainability strategy.

Let’s take a closer look at the measures for the sustainability goal of climate protection. Frankfurt has initiated three instruments here. Firstly, the Energy Department regularly organizes ideas competitions on the subject of climate protection. Secondly, the Environment Agencypromotesthe planting of new trees with “The Gifted Tree” by giving away a deciduous tree when a property is purchased. As a result, 1,100trees have already been planted. Thirdly, there is the climate promotion program “Frankfurt freshens up – 50 percent climate bonus”. This supports house and property owners, companies and housing associations in implementing climate-activemeasures. The city covers up to fifty percent of the costs. Such investments can include green roofs and façades, unsealing or even publicly usable shading and drinking fountains.

In 2023, Frankfurt published a guideline on climate-adapted urban square design. In future, squares are to become more user-oriented and offer cooling on hot days. Citizens will have a greater say in this. Adjustment screws“ also help to ensure that the guidelines are easy to implement. One reference for such a redesign is Paul-Arnsberg-Platz.

In the fight against the heat, Frankfurt alsowants tobecome a “sponge city”. To this end, it is optimizing the grey, green and blue urban structure and is relying on the support of Ferdinand Ludwig’s Chair of Green Technologies in Landscape Architecture at TUM with the research project “Integrated Strategies for Strengthening Urban Blue-Green Infrastructures (INTERESS-I)“. For example, INTERESS-I has been developing strategies, concepts, designs and concrete implementations for Frankfurt since 2018. The city is investigating all usage options from drinking water to industrial water. For sustainable urban planning, Frankfurt must also safeguard the coldair flows that ventilate the city center. To ensure that these air currents remain intact, large, contiguous green spaces are needed above all. This is why the existing and planned urban trees are being optimized in terms of number, type and location. However, not only greenery at ground level, but also green roofs and façades have a cooling effect on buildings and their surroundings. In the fight against the urban heat island effect, the city also advises low surface sealing, unsealing and materials with a high albedo. One example of this is the construction of the Sankt Philipp Neri daycare center. The redesign replaced asphalted ground with green spaces.

This year, the city passed one of the most progressive statutes in Germany for the greening of properties and buildings, the “Design Statutes for Open Space and Climate”. From now on, it obliges new buildings and conversions to have greenery on façades, roofs and front gardens. The open space statute is necessary because existing regulations (development plans, tree protection statutes, etc.) are not sufficient as climate adaptation measures. According to David Edelmann (Greens), the statute is a milestone. Rosemarie Heilig (Greens), on the other hand, would like to see more specifications and speed: “We have now experienced in three summers of drought how much the city can heat up. The only thing that can help is more greenery.“ But there is also criticism. From an economic point of view, the new regulations inhibit construction activity and increase building costs. The CDU/CSU would also like to see the already revised statutes toned down. There are concerns about restrictions on property rights. But shouldn’t the right to gravel areas on the roof or in the front garden, for example, be subordinated to the common good?

As far as new planning areas are concerned, climate protection criteria now have more weight in competitions and planning. Building projects must now undergo a “climate check” and respond to climatological studies. The city is also continuously raising awareness of climate change adaptation among itscitizens. It provides regularand transparent information about new measures via publications, websites, hotlines, apps, tours and exhibitions.

Unfortunately, Frankfurt’s climate protection measures with regard to Agenda 2030 are not yet very advanced. The city is also appealing to citizens to install drinking fountains on publiclyaccessible property. However, it has so far only installed a few clearly visible drinking water points. Furthermore, a climate department has only been in place since this year. The new position now combines the climate change-related content from the environment and energy departments. Time will tell how quickly decisions are made there and how the interfaces are defined.

At district level, the new Europaviertel district in Frankfurt may appear to be a good example. It is one of the first urban districts in Europe to achieve the platinum sustainability certificate – partly due to the positive local district climate. But the associated Europa-Garten stands out negatively. As one of Frankfurt’s newest parks, it was closed for years due to legal disputes. Now the area is in need of renovation and is still unusable.

In general, the past shows that despite extensive ideas, isolated measures as well as incentive and advisory programs from the municipal side are often not enough to achieve climate protection goals. The scope for regulatory intervention by local authorities remains limited. So what can help? More detailed legal requirements at federal and European level would make it easier to implement climate adaptation programs at local level. And don’t forget – processes such as “Fridays For Future” show that civic engagement can also make a difference.