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15.06.2023 - Ausgabe: 3/2023

On the way to sustainable and resilient urban development or how to achieve a transformation towards more openness and aesthetics

by Graduate Engineer and University Professor Christa Reicher (Aachen Institute for Urban Planning and European Urban Studies)
© nordenfan / stock.adobe.com

All over the world, cities and regions are currently facing comprehensive transformation processes: social and demographic change, climate change, scarcity of resources, digitisation and new technologies are only the major challenges. Not least, due to the recent Covid-19 pandemic and international multi-crises it has become even more clear how quickly the framework conditions can change and the pressure to act increases. Hence, we also have to rethink in the field of urban planning and development. There can be no "business as usual"; this would severely limit our quality of life and especially the quality of life of future generations.  

If we want to make the transformation sustainable and resilient, we need to use significantly fewer resources, focus on land recycling and approach circular planning and building with commitment at all levels. Consequently, ideas and wishful thinking about linear urban development are simply unrealistic. And this raises more than ever the question of how we should respond in urban planning and development to changes brought about by new drivers and crises.  

It starts with land consumption

Global developments are alarming with regard to land consumption: due to increasing urbanisation and population growth, it is estimated that 230 billion square metres will be built worldwide in the next forty year, which corresponds to the area of a metropolis like Paris per week (cf. ACE 2021). Thus, increasing land consumption is obviously one of the main drivers that urban development has to deal with and how crises can be countered. 

Every day, according to the Federal Statistical Office, an average of about 50 hectares per day are newly designated for settlement and transport areas in Germany (cf. Federal Statistical Office Wiesbaden, 2021). This means that the federal government's goal in the German sustainability strategy of limiting the average daily increase to less than 30 hectares by 2030 and reducing it to "net zero" by 2050 is still nowhere in sight. Open space is lost through land consumption and is thus no longer available for important ecosystem services, biodiversity and other uses, such as natural climate protection, food production and the expansion of renewable energies (cf. position paper UBA 2023:17). 

The reasons for the increasing land consumption are manifold: the demand for living space has been steadily increasing. The Federal Statistical Office put the average value for Germany in 2020 at 47.4 m² per person. On average, 0.2 m² are added per year (cf. Empirica Regio). And even the aspired circular land economy of not using any more land for settlement and transport purposes by 2050 seems to be a long way off. Yet land is a finite resource and further sealing must be avoided at all costs against the background of climate change. 

Redensification and land recycling in inner-city locations therefore play an important role, because they offer great potential in terms of land-use. Despite enormous development pressure on our cities, the motto "inner development before outer development" still applies to urban planning and urban development. From an urban development perspective, the development of abandoned or underused sites is of great importance because in this way not only the site itself is activated, but the revitalisation can also have a major stimulating effect on the neighbourhood and the larger spatial context of the city. In most cases, these areas have good connections to the existing infrastructure; the follow-up costs for development and connections to the public transport system can be reduced through higher utilisation. Conversion also offers the opportunity to reorganise existing urban structures and overcome barriers created by previous land use.

Accordingly, inner-city areas usually have many locational advantages. Often, these areas enjoy a particularly favourable location and are considered "prime real estate" in the context of urban development. In many cases, the existing infrastructure and development can also be used for new purposes, thus providing possibilities to create and implement new urban development concepts. 

The challenges of reducing the consumption of space by activating abandoned and underused land is thus a central adjusting screw for sustainable and resilient urban development, knowing that any vision for the future of a brownfield site must also take sufficiently into account the relevant climate and resource protection issues. 


Priority for "multiple internal development”

The current situation in our cities is also influenced by profound changes in the utilisation structure: Economic change is reflected not only in deindustrialisation but also in new forms of urban production and services. With the change from an industrial to a knowledge society, the question arises more than ever what consequences are to be drawn from the changing "business fundamentals" for the spatial organisation of the city: Living and working are increasingly being combined on a small scale. As a result of the Covid-19 pandemic, the relationship between living and working has changed. Home office seems to be a new normality for many professions. With the changes in the professional work, the need for office space is decreasing. 

And in general, production is becoming much more city-friendly, because technological progress has enabled us to produce in a more eco-friendly way, and the share of industrial production in total economic activity has been declining for many years. 

At the same time, retail is facing enormous challenges. The increasing online trade as a driver and amplifier of the crisis has for years called up the question of what the future of stationary retail is. The Covid-19 pandemic has acted like an accelerator for the decline of retail and led to serious vacancies of shop premises and other retail spaces. In the inner city, which was previously too mono-functional, this opens up new opportunities for creative uses and the return of production to inner city locations. Under the changed framework conditions, not only do the "old" uses rearrange themselves spatially, but they also constitute themselves differently and partly develop into "new" types of use such as commerce & tourism, industry & culture or co-working & living.  

The activation of underused areas represents an inner development that provides answers to the drivers and the multiple crises and that can also take on a compensatory function beyond an appropriate economic redensification. It should preferably encompass different contents and demands in the sense of "multiple inner development", i.e. it should be multidimensional and focus on long-term quality goals.  Accordingly, inner development should not only aim at increasing building density, but also fulfil the demand for diverse usage, an expansion and qualitative upgrading of the green space volume, the physical activity offer as well as the consideration of building culture and energy aspects. 

“Multiple inner-city development" is thus an important component of sustainable urban development, but it can only succeed if the various disciplines - at least urban, landscape and transport planning - work closely together and the different concerns are integrated into the planning process (cf. UBA 2022:15). The networking of the actors and their integration into a goal-oriented and transparent process design is a prerequisite for successful sustainable urban development. 


Open space and landscape as urban elements 

The conscious avoidance of building on inner-city areas and their long-term preservation as open spaces with a landscape character - also in an urban context - can be a good answer to the diverse drivers and crises. After all, city and landscape have long ceased to be traditional opposites, but are merely different expressions of the cultural imprint on our environment. For urban planning, this recognition means that the landscape must be understood as part of the city, and that the idea of landscape as complementary to the city seems outdated. Landscape can easily form an equal part of the urban fabric. At the same time, the function of landscape varies according to the respective situation. In an inner-city context, landscape can generally support and strengthen urbanity as an urban planning element. The idea of creating a city with landscape is therefore by no means absurd. On the contrary: it is obvious against the background of the effects of climate change. 

Climate change in combination with the density of buildings in cities is leading to increased heat events in cities, which have an impact on the well-being of residents and the overall quality of life. Against this background, urban green spaces are suitable for mitigating negative health effects due to their cooling function (Bowler et al. 2010). In addition to cooling, green spaces play an important role in terms of shading, water retention and water storage and thus make an important contribution to climate adaptation. A very central motto of sustainable urban planning must be to create as much space as possible for greenery and for water. Cities should ideally absorb CO2 in the future instead of emitting it.

The discussion about urban green-blue infrastructure, understood as a network of near-natural and designed vegetation- and water-dominated areas and elements in the city, is increasingly moving into the focus of urban development. Green-blue infrastructure provides a wide range of ecosystem services and at the same time contributes to recreation, physical activity and encounters. Within cities, green spaces are mostly distributed unequally: The central locations are often characterised by only few green spaces; there is a particular need for action here (cf. BBSR 2022:102f). At the same time, the Covid-19 pandemic has highlighted the problem of socially unjust distribution and accessibility of urban green and open spaces. 

With a view to this network and the corresponding urban spaces, it is important to ensure that they retain their quality of stay for all the different interest groups involved in the functioning of the complex system of the city. This means creating inclusive open and urban spaces that respond to the needs of local residents and at the same time are open and accessible to other stakeholders. Moderating conflicting or overlapping demands on urban open spaces through different, sometimes contradictory demands is a difficult task. It goes hand in hand not least with the danger of over-programming and over-design (cf. Reicher, Tietz 2022) and calls up questions about the openness of structures - also concerning the uncertainties we will have to deal with in urban development in the future. 


Resilience and openness to overcome competition 

In this phase of instability, one finding is becoming increasingly important in urban development: the importance of resilience in the face of disasters and the ability to independently renew our neighbourhoods, cities and regions after a crisis. Without resilience, no real progress will be possible in our society. In urban planning, "urban resilience", which also includes openness to new spatial constellations and the agreement of previously competing uses, thus takes on a whole new relevance. The Covid-19 pandemic will possibly be over at some point - the climate crisis, however, remains and will even intensify. 

A good concept of urban resilience must follow the criteria of climate change mitigation and adaptation. It is based on at least five competencies: 

  • Robustness: in the sense of being able to deal with disruptions in a resilient manner.
  • Flexibility: a flexible response to change 
  • Ability to learn: learning from crisis situations that have been overcome
  • Multi-disciplinarity: to pursue multidisciplinary approaches  
  • Holistic approaches: developing comprehensive and integrated solutions (cf. Council of the European Union 2013)

A resilient urban system encompasses almost all areas of life, from the provision of public services to a sustainable mobility concept, from resource-conserving urban development to climate-friendly urban design with usable unsealed green spaces. However, it must also include the participatory aspects, i.e. forms of participation and civil society engagement of the population. Process-oriented planning approaches that succeed to combine top-down and bottom-up approaches in an intelligent way are more sustainable today than ever before. Existing concepts and strategies do not become obsolete, but an integrated view and a dialogue-oriented planning process with local people is becoming increasingly important.

Resilience not only plays a role at the various spatial levels - from the neighbourhood, to the city, to the surrounding region - but is relevant for all levels of action in urban development. It is about actively adapting to and changing future challenges: "Urban resilience thus stands for a comprehensive culture characterised by a shared change of perspective that holistically brings together continuous learning, proven experience and visions for the future." (BMI 2021: 6). 

Richard Sennett analyses the social dimension of the city, the relationship between built and experienced space, in a very complex way in his book "The Open City" (2018). He asks what an open city that not only allows diversity, disorder and change, but also creates the necessary prerequisites, can look like. This aspect of open and hybrid use can be related to the open spaces, but also to the buildings - more than ever, home offices are found in the flats - and to the streets and traffic spaces as the car-poor city centres have been tried out during the lockdown without official regulations.

So the resilient city of the future must be sufficiently strong to withstand the contradictions of different interests, because it allows for spatial complexity and diversity while at the same time being open to the unpredictable. In resilient cities, the needs of the people and an orientation towards the common good are the focus of planning and practice. The Covid-19 pandemic and climate change have shown us that we need more than ever diverse, changeable and open spaces that help us to generate more quality of life.


The rediscovery of aesthetics as a sustainability factor 

The justified demand for openness in the sense of potential spaces that can react to the unforeseen must not have a negative influence on aesthetics. The aspect of aesthetics not only goes hand in hand with the demand for beauty and quality design, but is also closely linked to sustainability. The more aesthetic something is, the more worthy of preservation it is and the more prudent we are in dealing with it from the very beginning. We find it difficult to tear down and rebuild something that is perceived as beautiful. Buildings and urban spaces that are beautiful are usually preserved and well maintained. Aesthetics even belong to the "elementary needs of humans", according to Christian Illies in a Spiegel interview (Koerth 2018). 

Aesthetics also contribute to the quality of life, because an attractive and beautiful environment influences - consciously or sometimes unconsciously - our sense of well-being. In urban planning and development, social challenges find their answers in the built environment; these have to take into account aspects such as affordability and functionality, but also meet the demand for design quality. Aesthetics is therefore not a contradiction to the desired openness and resilience, but is above all a contribution to sustainability. 

This claim is also pursued with the concept of the "New European Bauhaus" (NEB), initiated by EU Commission President Ursula von der Leyen in 2020. "The New European Bauhaus aims to create a new lifestyle that reconciles sustainability with good design, requires less carbon and is inclusive and affordable for all." (Cooperation international 2021). Aesthetics, sustainability and inclusion, as called for by the "New European Bauhaus", are mutually dependent and place the concern of attractiveness at the centre of our actions. Attractiveness means more beautiful, sustainable and inclusive forms of living together.

Quality is more important than quantity. Quality public spaces and sophisticated architecture increase the attractiveness of a city and a region and thus make an important contribution to the quality of life. At the same time, good design increases the value of real estate and the urban yield in the long term.


How can a sustainable transformation succeed? 

Multi-disciplinarity and holistic approaches to solutions create the foundations for shaping the upcoming complex planning processes towards resilience, aesthetics and openness of cities and rural spaces.

In order to achieve a successful sustainable transformation, the great significance of public green and open spaces in cities for the well-being of the population will have to be appreciated. This provides the basis for a paradigm shift in urban planning: the unconditional praise of structural densification must be replaced by conditional praise that attaches greater importance to public and private open spaces without disregarding the social concern - the creation of living space. In other words, densify in the right places and consciously preserve open space elsewhere and protect it from development. 

Moreover, planners must be aware that all strategies and concepts that we develop and design today must take into account the needs of the future generations. The implementation will take many years, during which the framework conditions may change again. 

Accordingly, for the cities of the future, it is of utmost importance not only to focus on individual aspects in the sense of multi-disciplinarity, but to pursue a decisive paradigm shift through a cross-linked and networking approach. Because more openness and aesthetics will lead the way to sustainable and resilient urban development.



ACE – Architects’ Council of Europe (2021): A sustainable, fair and beautiful built environment to address the climate and biodiversity crisis. Brüssel, 28.10.2021

Bowler, D.;  Buyung-Ali, L.; Knight, Tm; Pullin, As (2010): Urban greening to cool towns and cities: a systematic review of the empirical evidence. Landsc Urban Plan 97: 147-155 

Bundesinstitut für Bau-, Stadt- und Raumforschung (BBSR) (2022): Wie grün sind deutsche Städte? 03/2022, Bonn 

Bundesministerium des Innern, für Bau und Heimat (BMI) (2021): Memorandum Urbane Resilienz. Wege zur robusten, adaptiven und zukunftsfähigen Stadt, Berlin 

Council of the European Union (2013): Council conclusions on EU approach to resilience, Brüssel 

Difu (2017): Was ist eigentlich...Transformation, Berlin 

Empirica Regio (2021): Wohnungsmarktbeobachtung. 

Online verfügbar unter: https://www.empirica-regio.de

Neike, C.; Schreier, J.  (2020): Städte müssen smarter und anpassungsfähiger werden. Online verfügbar unter: https://www.bandbreite.io/staedte-muessen-smarter-und-anpassungsfaehiger-werden-a-932056/

Koerth, K. (2018): Viele Bauen hässliche Häuser, das ist fatal. In: Spiegel Kultur,   26.08.2018

Kooperation international (2021): Neues Europäisches Bauhaus: Verbindung von Nachhaltigkeit mit Stil und Inklusion. Verfügbar unter https://www.kooperation-international.de/aktuelles/nachrichten/detail/info/neues-europaeisches-bauhaus-verbindung-von-nachhaltigkeit-mit-stil-und-inklusion/

Reicher, C.; Tietz J. (2022): Atmende Städte. Zukunftschancen für Stadt und Land mit und nach Corona, Wiesbaden (ISBN 978-3-658-37758-8)

Sennett, R. (2018): Die offene Stadt. Eine Ethik des Bauens und Bewohnens. Zweite Auflage. Hanser, Berlin

Statistisches Bundesamt (2021): Siedlungs- und Verkehrsfläche. Online verfügbar unter: https://www.umweltbundesamt.de

Umweltbundesamt (UBA) (2022): Dreifache Innenentwicklung. Definition, Aufgaben und Chancen für eine umweltorientiere Stadtentwicklung, Berlin 

Umweltbundesamt (UBA) (2023): Positionspapier Umwelt und Klima schützen – Wohnraum schaffen – Lebensqualität verbessern, Berlin 



Prof. Christa Reicher has been Chair of Urban Planning and Design and Director of the Institute for Urban Planning and European Urban Studies at the Faculty of Architecture at RWTH Aachen University since October 2018. She has held the UNESCO Chair "Cultural Heritage and Urbanism" since 2023. 

In 1993 she founded the international planning office RHA REICHER HAASE ASSOZIIERTE with offices in Aachen and Dortmund.

In 2022 she has been awarded the Grand Prize for Building Culture by the Association of German Architects and Engineers (DAI). 

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