Between asphalt and concrete

Anyone looking for green spaces in major German cities may have to search for a long time in some places: streets and bike paths are paved, trees and meadows are giving way to new buildings and parking lots. And every day, new areas turn gray. Experts see municipalities facing a mammoth task: in order to protect people from the consequences of the climate crisis, such as heat waves and flooding, cities must be rebuilt. But is that happening?

CORRECTIV, in collaboration with Vertical52, a platform for satellite journalism, has investigated the urban sealing of three German cities: Leipzig, Hamburg, and Stuttgart. Using images from the Sentinel 2 satellite, we are showing for the first time which neighborhoods are particularly affected by asphalt and concrete and where urban sealing has increased the most. And we have found surprising results that are representative of many cities in Germany.

Despite official commitments to climate adaptation, soil sealing is increasing in all three cities. Leipzig, for example, has set itself the goal of planting 1,000 new trees each year. At the same time, between 2018 and 2024, eight square kilometers of green space were lost, an area equivalent to 1,120 soccer fields.

Leipzig, often perceived as a “green oasis,” is more sealed than one might think. Between 2018 and 2024, the proportion of concrete and asphalt surfaces rose from 29.2 to 31.2 percent—an increase of about six square kilometers.

Stuttgart, on the other hand, often perceived as the epitome of an industrial city, is surprising: since 2018, green spaces have increased by one square kilometer, which is about 0.5 percent of the city's area. Noteworthy is the targeted unsealing of already heavily built-up neighborhoods such as the Europaviertel or around the city hall. Overall, however, the amount of sealed land in the capital of Baden-Württemberg is also increasing by one square kilometer.

None of the three cities has concreted and asphalted as much as the Hanseatic city of Hamburg: 14 square kilometers – an area about five times the size of the St. Pauli district – were newly sealed between 2018 and 2024.

Concrete is poured elsewhere for unsealing

The three cities are examples of a trend throughout Germany: where green spaces and fallow land once acted as natural air conditioners, absorbing rainwater and providing habitats for insects, birds, and small rodents, concrete and asphalt now dominate. However, densely built-up urban residential areas are particularly affected by extreme weather such as heat and heavy rain.

According to Anja Bierwirth, an expert in sustainable urban development at the Wuppertal Institute for Climate, Environment, and Energy, cities need to de-seal more than they seal in order to adapt to the consequences of the climate crisis. The often touted goal of “net zero,” i.e., removing as much concrete and asphalt as is sealed, is not enough. This is because every sealed and built-up area is lost and needs “many decades or centuries to regain the same ecological value it had before it was sealed,” she says.

Our satellite analysis shows that heavily sealed urban areas such as Hamburg's old town, Stuttgart's main railway station, and Leipzig's eastern city center turn into saunas in summer. Our analysis shows that it is on average up to seven degrees hotter there than in other districts, which affects people with pre-existing conditions, older people, and children in particular. Homeless people in particular lack protection. And the burden is increasing: 2024 was the hottest summer since records began over 80 years ago.

Concrete surfaces also become a problem during heavy rainfall: sewers overflow and basements and parking garages fill with water. In the worst case, it is not only people's health that is threatened, but also their livelihoods and safety, as the flooding in the Ahrtal showed.

Municipalities and cities are heading unprotected into a climate emergency

It is primarily cities and municipalities that can protect their residents from extreme weather and green their streets and squares: they decide whether areas are to be unsealed or built on. However, in many places, people are knowingly heading toward a climate emergency without taking any protective measures.

In 2023, only one in three counties stated in a survey conducted by CORRECTIV, BR, NDR, and WDR that they would unseal land to cool cities during heat waves. The number is probably even lower: the statistics are missing more than 70 of the 400 counties and independent cities that did not respond at all.

The federal government is aware of the problem. The Federal Ministry for the Environment states on its website that reducing land consumption is a key environmental policy concern. Every day, Germany loses 52 hectares of land to new housing developments and transport routes – equivalent to 72 soccer fields.

However, the federal government quietly postponed the target of its sustainability strategy to reduce land consumption from 2020 to 2030. Germany and the European Union do not even intend to achieve “net zero,” i.e., only sealing as much land as is freed from concrete and asphalt, until 2050.

Local authorities must consider climate adaptation

But why are cities finding it so difficult to stop soil sealing? One reason is that departments within city administrations are strictly separated from one another. However, climate protection and adaptation affect all areas of administration. Nevertheless, they are often assigned to a single department or the climate management office. The result is contradictory urban development: a green, nature-oriented square is created next to a department store with ground-level parking spaces instead of space-saving underground parking or rooftop parking spaces.

When it comes to new construction projects, builders often take a radical approach: decades-old trees and shrubs are cleared and the construction site is concreted over. Later, a landscape architect plants individual bushes to supposedly compensate for this. The main thing is that they are easy to maintain. This is a problem in schools, among other places: instead of preserving green spaces, schools have to buy and install sun sails in the playground to protect children and young people from the heat.

City expert Bierwirth criticizes: “What is the plan for adapting our schools to climate change—just have more days off when it's hot?” She warns: “Then some children go home to cramped, overheated apartments with no garden or park outside, while others can study in a well-air-conditioned house with a garden.” In urban development, everyone needs to consider the dimension of climate change adaptation – right from the start.

Germany is fundamentally good at rebuilding and reconstructing, says city expert Bierwirth. “But we lack experience and tools for rebuilding cities and adapting them to new situations.” As a result of the war, many cities were destroyed, which Germany rebuilt.

For Bierwirth, Germany is currently facing a reconstruction task “on a scale we have never seen before.”

Empty offices, lack of housing: building regulations exacerbate space shortage

Another problem is building legislation. So far, building and planning laws haven't really been adjusted to deal with the effects of climate change. For example, if a property owner wants to build a residential building on their land and it fits in with the surrounding area, the local authority cannot simply reject the plan on climate protection grounds. What's more, many cities are facing an acute housing shortage. Our analysis of satellite data shows that residential construction is one of the main reasons why new land is being sealed.

This is also the case in Stuttgart: A spokesperson for the city wrote to CORRECTIV in response to an inquiry, stating that one of the largest projects is the Böckinger Straße residential quarter. There, 5.5 hectares of land previously used primarily for agriculture or horticulture are being resealed to create 400 residential units. The neighborhood is located in the Rot district, one of the areas where land sealing has increased the most between 2018 and 2024.

The Stuttgart branch of the environmental organization BUND sharply criticizes the project, writing in a statement that the city is disregarding its own requirement not to build on greenfield sites. At the same time, thousands of office spaces stand empty in the city center – but converting them into residential space is difficult. “In the seven largest cities in Germany – including Stuttgart – 60,000 new apartments could be created by converting vacant office space,” says Pfeifer. And this could be done without sealing new land or further densifying the already densely built-up city center. However, this would require cities to change their development plans, which could take years in larger cities.

The Federal Ministry for Housing, Urban Development and Construction, headed by Klara Geywitz (SPD), is currently working on an amendment to the Building Code to defuse such conflicts. Local authorities are to be given more leeway to convert commercial space into residential space. Whether this will succeed in practice remains to be seen.

Hamburg has been dragging its seal removal plan for four years

In Hamburg, too, the desire for new living space is winning out over green space. “Urban development projects such as those in Oberbillwerder or Fischbecker Rethen, which together involve the development of 170 hectares of agricultural land, are problematic,” says Christian Gerbich, nature conservation officer at the environmental association NABU Hamburg. But there are alternatives: “Along Hamburg's main thoroughfares, there are often single-story houses or supermarkets with parking lots that could be used more effectively for additional living space,” says Gerbich.

According to environmental groups and local folks, dependence on investors is driving urban sealing in all three cities. When a district is thinking about whether to build a new Lidl or Edeka supermarket, it's easy for an industrial park to replace green space on the agenda. To keep investors happy, the city doesn't require that apartments and underground parking be built above the supermarket. Then, as is so often the case, a new parking lot is built next door.

“The districts are responsible for development planning,” says Gerbich, “the Senate has no say in the matter.” Although the government could theoretically set targets, the districts would resist concrete guidelines from above. There is no legal instrument to ensure that national targets are implemented at the local level.

This decentralization means that the districts rely on the others to do something. The result: there is no holistic view of the city.

Particularly bitter: back in 2020, the Senate promised a plan for how to successfully unseal Hamburg. Four years later, there is still no concept. When will it come? “Publication dates have not yet been set,” the Hamburg Authority for Environment, Climate, Energy, and Agriculture wrote in response to a CORRECTIV inquiry.

At least the city set up a heat hotline for citizens last year and is working on a heat action plan.

Stuttgart, of all places, is greening more than others

Our analysis revealed another surprise: when new sealing takes place, it is often in affluent districts outside the city center, such as the Freiberg district in the north of Stuttgart. There, the sealed area increased by around 11 hectares between 2018 and 2024 – equivalent to 15 soccer fields.

Yet Germany does not lack housing: on average, only two people now live in each household. Often, it is older people for whom the space has become too large. At the same time, young families in many large cities are desperately searching for affordable housing. The solution could lie in affordable and sensible home swaps. However, the necessary instruments for this are currently lacking.

At least Stuttgart is on the right track overall: between 2018 and 2024, around 207 square kilometers of urban land were newly sealed.

However, according to a spokesperson responding to CORRECTIV's inquiry, Stuttgart has not designated any new areas for industrial and commercial use for years. Our satellite analysis shows that, unlike Hamburg and Leipzig, Stuttgart is unsealing rather than sealing heavily sealed neighborhoods such as Europaviertel, Bruckwiesen, and Am Rosensteinpark. The city also plans to protect its citizens from heat waves with green spaces. But progress is slow—our satellite analysis shows that only one square kilometer of green space has been added in six years. “There is considerable resistance when parking spaces are removed, especially from businesses that fear this will threaten their existence,” says Gerhard Pfeifer, managing director of the Stuttgart Regional Association of Friends of the Earth Germany (BUND). Stuttgart's basin location could be particularly dangerous during heavy rainfall.

This causes torrential streams to form, which rush towards heavily sealed areas such as the main station, city hall, and the Europaviertel district. “We have proposed several oversized streets that could be dismantled to unseal areas,” says Pfeifer. “They are located on the slopes of Stuttgart, which are prone to flooding during heavy rainfall.”

Leipzig in the flood zone: Sealing also increasing in the city center

Leipzig also needs to protect itself from flooding. The city, which has seen the strongest growth in Germany over the past 20 years, is one of the ten municipalities most at risk from river flooding in Germany. Land sealing is progressing here, mainly to create housing, and former war wastelands are being built on.

The districts of Neulindenau, Plaußig-Portitz, and Zentrum-Südost and -Ost are particularly affected, according to satellite analysis by CORRECTIV and Vertical52.

Upon request, Leipzig's Office for Urban Greenery and Waterways stated that the city wants to make urban growth space-efficient and preserve green and open spaces, for example through the multiple use of buildings and open spaces. Although the amount of green space per Leipzig resident has been declining steadily since 2017, “the area of public green spaces and parks has remained stable since 2020.”

According to Niclas-Robin Rosendahl from Ökolöwen Umweltbund Leipzig, the city is not as green as it seems at first glance. He cites the Millennium Field as an example of the lost battle for green spaces. The 2.3-hectare brownfield site is located in Lindenau, one of the ten of Leipzig's 63 districts where land sealing has increased the most in percentage terms since 2018.

“The International School Leipzig, Leipzig's largest campus for 1,600 students, is to be built on the Jahrtausendfeld,” says Rosendahl. The private school is far too large a construction project for the last large open space in the west of Leipzig. Ironically, the city itself classified this area as particularly worthy of protection in a climate analysis. Nevertheless, it is now threatened by sealing.

Wilhelm-Leuschner-Platz is also causing controversy. The square is around six hectares in size and is located south of the city center in the Zentrum-Süd district. Starting in fall 2024, the city will develop the square with apartments, office space, and playgrounds, among other things.

René Sievert, chairman of NABU Leipzig, criticizes the fact that decades-old trees have been cleared for the development—even in areas where no buildings will be constructed. Replacement plantings will never be able to replace the old trees, he says. “As is so often the case, the city did not investigate the impact of the construction plans on nature and biodiversity in advance,” he told CORRECTIV.

Since 2019, NABU has organized rallies and vigils, demonstrated on site when the old trees were cleared in 2023, and even filed an urgent lawsuit, which was unsuccessful. “In the main proceedings, the content of our evidence was not even addressed,” Sievert says. The Higher Administrative Court is currently reviewing the appeal.

For Tobias Peter, city councilor and leader of the Green Party faction in Leipzig's city council, the developments on Wilhelm-Leuschner-Platz are a step in the right direction: "Seventy percent of the square is already sealed, which is anything but a green oasis. Ökotopia, the winning design in the open space competition, on the other hand, envisages extensive unsealing and species-rich greening of the western half of the square with numerous hedges and 50 preserved and 130 additional trees." According to the design, extensive unsealing and species-rich greening with hedges and trees is planned.

The Green Party has pushed through a city council resolution stipulating that, starting in 2030, no more land will be sealed than unsealed throughout the entire city. Rosendahl is skeptical: “Leipzig is generally good at coming up with nice-sounding concepts. But when it comes to implementation, that's where the difficulties arise.”

In all three cities examined—Hamburg, Leipzig, and Stuttgart—it is primarily environmental initiatives that are fighting for every square meter of unsealed soil. And in doing so, they encounter resistance and bureaucratic hurdles. Sievert from NABU Leipzig sums it up: “You have to put in a maximum effort to achieve a small thing.”