An analysis of the urban space Bayerischer Bahnhof with the focus on nature
In our last post, we reported our impressions and perceptions of the nature of the abandoned land. We would now like to take a closer look at some aspects of the area and its surroundings.
Nature in cities has many functions. It provides the basis of life for many plants and animals. In addition, it also has positive effects on people in the city.
In this article, we examine the current state of the abandoned land and point out the natural importance of abandoned lands in various aspects.
Regarding the upcoming constructions, it is even more essential to recognize the current state of nature and its importance. It has to be incorporated into the planning processes. Urban abandoned lands offer the opportunity to experience nature in an unregulated way. They exist as a habitat for plants and animals without profound interference by humans, such as fertilization and pesticides. The free development of nature like this can hardly be found elsewhere in the city.
One might think that it is more difficult for animals and plants to adapt to changed habitats, such as the abandoned land behind the portico of the Bayerischer Bahnhof, as they are strongly influenced by humans. The application of artificial sediments such as crushed stone or gravel sometimes modify the soil composition. Occasionally, sections of soil on inner-city brownfield sites are also completely sealed due to the use of concrete.
Contrary to this assumption, rare species of organisms often live in these overgrown areas. Species diversity, especially on older fallows, is often significantly higher than in the intensively used cultural landscape in the wider urban environment. Therefore, living organisms can develop here with less human influence. They provide important sanctuaries for animals and plants in densely built-up cities.
During our walk on the abandoned land, we could already identify some plant species. Most of these can be assigned to the strong herb layer typical for ruderal vegetation. In the area, we found species of ragworts, woodland vines, mullein, stinging nettles, and camomile.
Depending on the previous use, a variety of biotopes and small-scale habitats can develop on abandoned lands. Many areas have extreme conditions such as nutrient deficiency, drought, and heat and therefore harbor specialized animal and plant species. The free development of nature also creates habitats that are rare in the rest of the city.
Locusts, for example, tend to use dry areas rather than urban habitats. Heat-loving species such as the blue-winged grasshopper are highly endangered and live mostly in patchy and low-growing ruderal grasslands. For the lack of suitable habitats, specimens have moved into inner and outer city areas.
Ruderalized and sparsely overgrown older fallows can be habitats of the strictly protected sand lizard. Some of these rare reptiles were found on the brownfield at Bayerischer Bahnhof. Volunteers captured the lizards sporadically and relocated them to a new habitat in Zschepplin.
Besides, habitats of the protected European green toad were found in the area. This toad species had found a place to spawn in soil depressions filled with rainwater. Construction work and clearings on the abandoned land destroyed the habitat , according to a statement of Ökolöwe,
Green structures are of particular importance in cities. For residents, they provide a balancing function of the hectic city life.
In the following, the quantity and accessibility of green spaces in Leipzig will be examined with an emphasis on the area surrounding Bayerischer Bahnhof. Leipzig has a total area of 29781 ha. A total of 15139 ha of the city’s territory are “green”. The expression “green” includes forest, recreational and agricultural areas. In the diagram, it is apparent that Leipzig is about 50% “green”. However, only 18.18% are usable forest and recreational areas. Established parks occupy an area of only 516 ha, which is just under 3% of the city’s area.
Although Leipzig has a lot of green spaces, only some of these open spaces can be used by people. Created parks constitute new open and recreational spaces, especially in inner-city neighborhoods. An average of 15.9 m2 of open space is available to a Leipzig resident. However, due to uneven distribution across the city districts, this is not the case for every resident.
The accessibility of green spaces for inhabitants around the area of Bayerischer Bahnhof requires further investigation. The “Integriertes Stadtentwicklungskonzept Leipzig 2030”, assumes an open space of at least 2000 m². This area must be 250 m as the crow flies and about 5 minutes walking distance from the residences. Especially in “Südvorstadt”, it is striking how many residential areas have no access to open space, which the red area on the map indicates. The majority of the remaining residential areas have direct access to open space. Though, a resident only has 3 – 6 m² for their sole use.
Comparison to other green spaces
It is the aim of Leipzig’s urban development program to have a minimum provision of 6 m2 per resident. Due to population growth, the supply of open space per resident will continue to decrease. Consequentially, the problem intensity will increase, pointing to the need for a new city park in this area.
The abandoned land with a size of approximately 35.1 ha is one of many in Leipzig. Spanning approximately 3.3% of the city area, abandoned lands in Leipzig currently occupy about the same area as the landscaped parks and green spaces. As a part of the revitalization, a city district will replace this abandoned land, having a new park of about 8 ha. Within a radius of one kilometer, residents might visit the “Friedenspark” and the “Clara-Zetkin-Park“.
While “Friedenspark” was an old cemetery before, “Clara-Zetkin-Park” consists largely of wooded areas. “Friedenspark” is already an established park to the east of the abandoned land. The new park could be especially valuable for residents living in the west of the abandoned land, guaranteeing available open spaces.
Compensatory areas and replacement measures
The compensatory areas and replacement measures for the construction of the “City-Tunnel-Leipzig” (CTL), which was completed in 2013, must also be taken into account. These were defined utilizing the planning approval procedure of 2000-05-19. The plan amendment in 2004 preceded with the implementation in 2013 and 2014, with financial resources amounting to about 500000 €.
In total, there are three sub-areas. One of the areas (1) is located on the tunnel area south of the portico. Three measures have been formulated: Measure Bi/E4, Bi/E3, and Bo/E1. The content of these, you can read in the following paragraph.
The measures included the dismantling of the former unused railroad facilities of the Bayerischer Bahnhof. A 50 m wide air corridor between the tunnel portal and the stop “Bayerischer Bahnhof” was agreed upon. In addition, native shrubs were planted and bicycle and footpath connections were created. In order to create a green area that connects biotopes, an additional 860 m² of shrub-like, woody plants with fringe zones in form of grasses and perennials were seeded.
The two further partial compensatory areas are located south of the tunnel portal up to the stop “Semmelweisstraße” (2) and further up to the level of the locomotive shed (3). Measure Bi/E7neu was created for this purpose in the 2004 plan amendment procedure. It included the seeding of lawn and the planting of native, site-appropriate groups of trees to develop and maintain an extensive meadow area. Bicycle and pedestrian paths were also constructed in this area on both sides of the passage.
The measures aim to compensate for the loss of the previous vegetation. New habitats for fauna and flora should will arise and thus ensure the climate compensatory function of the area. The creation of public green spaces, which invite citizens to spend time there, should contribute to an improvement of recreational and open space use in the urban area. They would also interconnect zones with already existing and planned green spaces in the surrounding area.
The location of all compensatory areas was taken into account in the “Stadtraum Bayerischer Bahnhof” planning approval process. The future urban district park will integrate them in zones 5a, b, c. However, a current inventory of the city in the future neighborhood “Lößniger Straße” shows that only less than 50% of the woody plants planted at that time have survived. Therefore, they need to be replaced. During our visits to the site, we were also able to notice a low recreational and open space use of the green areas by residents. Also, the goal of creating an interconnected structure with surrounding green spaces will probably only be realized through the creation of the future park.
In a city, it is impossible to identify a single urban climate. Rather, there are many small microclimate areas where hot and cold can be right next to each other.
The Bayerischer Bahnhof abandoned land is an air-pollution climate remediation area. This means that the abandoned land and the vegetation can contribute to the relief for the urban climate. We discuss three climate issues at Bayerischer Bahnhof below.
There are four measuring stations for air pollution in Leipzig. The Saxon State Office for Environment, Agriculture and Geology (LfULG) carries out the measurement with the program IMMIKART GIS. Data of the measuring stations serve the calulations of air pollution values for other locations. Due to the surrounding traffic, the abandoned land suffers from a particular emission load of nitrogen oxides. This shows the map from 2018.
Medium air pollution levels affect the streets around the fallow. No limits were exceeded. It is important to keep NO2 levels low, as they can damage plants and in some cases contribute to soil acidification.
The areas around the abandoned land, especially “Südvorstadt” are built very densely. Intensive development reduces the night-cooling. The roofs of the buildings heat up strongly during the day and release the heat at night. As a result, the area around Bayerischer Bahnhof is an area of intense overheating. It exacerbate the risk of disturbing the balance between heating and cooling. Especially “Südvorstadt” and neighborhoods close to the city center are concentration points of nocturnal heat islands. Due to a lot of shadow-casting buildings, densely populated urban areas can be cooler than rural areas during the day, but at night the buildings emit heat. On the one hand, urban greenery lowers the air temperature through shading and evaporation. On the other hand, the abandoned land provides an important air exchange path, permitting the cooling of the surrounding neighborhoods.
The warm rising air in the city leads to low-pressure areas near the ground. Cold air from the surrounding areas flows in. However, this inflowing air can be modified and diverted by various obstacles, such as buildings, trees, and hills. This abandoned land acts as an corridor transporting air into the city.
The north-south ventilation pathway provides an important thermal balancing function. It is responsible for the reduction of heat and air pollution. Often, railroad tracks like the “Bayerischer Bahnhof” also provide an air corridor. Compensation currents can penetrate far into the urban area and thus also positively change the urban climate of Leipzig. It is important to maintain these corridors and not to interrupt or even prevent the exchange of air by high buildings.
Thanks to our visit to the abandoned land and the analysis, we are more aware of the importance of this area. However, due to population growth, the demand for housing in the city increases tremendously. Over the last 6 years, the growth has averaged at about 1.45% per year. Therefore, the planned apartments in the new neighborhood are imperative. In order to protect the city climate and prevent the intense overheating of the area, it is of immense importance to preserve the air corridor. The protection of biodiversity and urban greenery is a key task of sustainable urban development and must be taken into account. For the population living in the city, it is important to provide a natural compensatory area.