Manuel Wolff

The impact of urban regrowth on the built environment

After several decades, an increasing number of European cities have been experiencing population growth after a longer phase of decline. This new growth represents not just a quantitative phenomenon but also has qualitative implications for the urban space and the built environment. A juxtaposition of re- and de-densification, as well as changes in land use, in the form of a small-scale spatial mosaic, can be observed. A crucial factor for estimating the relationship between the built environment and demand for it is population density. Increasing population densities may put pressure on sustaining a certain quality of life and on ecological recovery spaces. In this vein, an indicator concept for re- and de-densification will be applied to the city of Leipzig, one of the most illustrative examples of a regrowing city, in order to shed light on the complex relationship between changing human housing demands and their impact on land use. The concept involves measuring population density. Our study has demonstrated that, although similar density changes can be observed in different periods in different parts of the city, they are dominated by different drivers, leading to the formation of different spatial patterns. The results of our study emphasise that regrowth should be understood as a distinctive process because it is distributed very heterogeneously within the city area, with a variety of spatial effects and impacts. The concept allows us to draw conclusions about processes that mitigate, drive or reinforce regrowth, and therefore contributes to a better understanding of this phenomenon and its implications for land use.

Urban growth and decline: Europe’s shrinking cities in a comparative perspective 1990–2010

At the beginning of the 21st century, the phenomenon of shrinking cities was widely discussed across Europe. Most European countries saw an increasingly ageing population and an internal migration from underdeveloped to more competitive locations. Since the turn of the century, and in contrast to the past, a great deal has been written about the causes and impacts of shrinkage, as well as about policies and planning strategies. However, the state of knowledge in a cross-national comparative perspective is rather poor because, to date, studies have basically analysed large cities and empirical evidence hardly shifts attention to the contextual influence on local dynamics. Against this background, this paper fills the gap between macrotheoretical conceptualisation and empirical observation by testing a heuristic model of urban shrinkage encompassing the whole range of cities in Europe. The paper questions to what extent urban shrinkage represents a broader trend in Europe in terms of both duration and distribution, and aims to investigate the influence of economic and demographic drivers on the non-linear evolution of shrinking cities in Europe. Thereby, the spatial distribution of different trajectories of shrinking cities in urban Europe in the period from 1990 to 2010 will be presented in a comprehensive survey which reveals that 20% of European cities experienced shrinkage between 1990 and 2010, whereas 883 cities face recent shrinkage.

Wohnungsleerstand in Deutschland. Zur Konzeptualisierung der Leerstandsquote als Schlüsselindikator der Wohnungsmarktbeobachtung anhand der GWZ 2011

ZusammenfassungDer Wohnungsmarkt in Deutschland ist derzeit von gegensätzlichen Tendenzen geprägt: Angespannten Märkten mit zum Teil ausgeprägter Wohnungsknappheit stehen entspannte Märkte mit hohen, zum Teil sogar sehr hohen Wohnungsleerständen gegenüber. Für beide Situationen ist die Leerstandsquote eine maßgebliche Bezugs- und Messgröße, sie fungiert als Indikator für die Bewertung. Jedoch ist die Leerstandsquote bislang kein systematisch untersuchter bzw. elaborierter Indikator, sie wird in den unterschiedlichen wissenschaftlichen und politischen Diskursen unterschiedlich quantifiziert und qualifiziert. Hier setzt der Artikel an, indem er auf der Basis einschlägiger Literatur eine systematische Kategorisierung von Leerständen vorschlägt und eine Heuristik für die differenzierte Bewertung von Wohnungsleerständen aus verschiedenen Perspektiven entwickelt. Diese Heuristik wird anschließend mit den Daten der Gebäude- und Wohnungszählung (GWZ) 2011 empirisch veranschaulicht. Anhand dessen kann gezeigt werden, dass zwar der Großteil deutscher Kommunen eine angemessene Leerstandsquote zwischen 3 und 5 % aufweist, jedoch erhebliche regionale und raumstrukturelle Unterschiede auftreten. Aus der Analyse der Leerstandsquoten können insofern keine flächenhaften Generalisierungen bzw. vereinfachende Aussagen für die Wohnungs- bzw. Stadterneuerungspolitik abgeleitet werden. Dies macht deutlich, dass die Leerstandsquote der Qualifizierung bedarf, wenn sie für planerische und politische Entscheidungen genutzt werden soll.AbstractAt present the housing market in Germany is characterized by contrary trends: Strained markets with partly distinct housing shortage are facing each other with relieved markets even with very high vacancies. For both situations the vacancy rate is a decisive indicator for evaluation. However, the vacancy rate so far is not systematically investigated and elaborated as an indicator but rather is quantified and qualified differently by various scientific and political debates. Against this background the paper suggests a systematic categorization of vacancy rates based on relevant literature. Additionally it develops a heuristic for a differentiated evaluation of housing vacancy rates from different perspectives. This heuristic is then backed up empirically by data from the building and housing census (GWZ) 2011. Thus, it can be demonstrated that the majority of German municipalities has indeed a moderate vacancy rate between 3 and 5 %, but also that substantially regional and spatial-structural differences appear. In respect of the analysis of vacancy rates no spatially-extensive generalization or simple conclusions for housing and urban renewal policies can be drawn. This underlines that a qualification of vacancy rates is necessary in order to be utilized for planning and political decisions.

From Shrinkage to Regrowth: The Nexus Between Urban Dynamics, Land Use Change and Ecosystem Service Provision

Urban shrinkage, commonly understood as population loss of an urban area, and post-shrinkage regrowth have become prominent pathways of urban development across Europe. While many cities, mostly in Eastern Europe, are still shrinking today, other cities that shrunk in the past now see new growth. Numerous cities have undergone this transformation from shrinkage towards new growth within only one or two decades – a relatively short time. Both shrinkage and regrowth have considerable impacts on urban land use, be it on densities or types of use. Both offer a variety of potentials and risks for sustainable use of urban land as well as for the provision of green spaces and urban ecosystem services (UES). On the one hand, there is the risk that new growth after shrinkage puts pressure on the qualities that emerged and/or were created in the time of shrinkage such as less density, more green areas, or spaces for experimentation and innovation, will be questioned in their existence and benefit. On the other hand, regrowth after shrinkage offers the great opportunity to make use of those qualities in order to build more sustainable regrowing cities and to ensure good provision of environmental qualities and ecosystem services for large segments of the population. Here, many trade-offs emerge, and many new challenges have to be addressed. Often, there is a complex setting of actors and interests that make it complicated to negotiate solutions.

State rescaling and economic convergence

ABSTRACT This paper critically engages with State/Space theory by interrogating the soundness of its fundamental assumptions regarding the rescaling of capitalism and by questioning the validity of its proposition about ever-rising spatial imbalances and economic divergence in post-1970s’ Europe. The paper employs descriptive, cartographic and econometric analysis of the regional and urban growth data covering 28 European Union countries and 11 major OECD and BRICS economies. The vast volume of multi-scalar evidence presented here cannot substantiate the central rescaling hypothesis about Europe’s increasing spatial disparities. A set of alternative explanations is proposed to account for the reported European economic convergence trends.

Compact or spread? A quantitative spatial model of urban areas in Europe since 1990

Changes in urban residential density represent an important issue in terms of land consumption, the conservation of ecosystems, air quality and related human health problems, as well as the consequential challenges for urban and regional planning. It is the decline of residential densities, in particular, that has often been used as the very definition of sprawl, describing a phenomenon that has been extensively studied in the United States and in Western Europe. Whilst these studies provide valuable insights into urbanization processes, only a handful of them have reflected the uneven dynamics of simultaneous urban growth and shrinkage, using residential density changes as a key indicator to uncover the underlying dynamics. This paper introduces a contrasting analysis of recent developments in both de- and re-concentration, defined as decreasing or increasing residential densities, respectively. Using a large sample of European cities, it detects differences in density changes between successional population growth/decline. The paper shows that dedensification, found in some large cities globally, is not a universal phenomenon in growing urban areas; neither the increasing disproportion between a declining demand for and an increasing supply of residential areas nor actual concentration processes in cities were found. Thus, the paper provides a new, very detailed perspective on (de)densification in both shrinking and growing cities and how they specifically contribute to current land take in Europe.

On the Connection Between Urban Sustainability Transformations and Multiple Societal Crises

Crises are a frequent companion of global urbanization; within the last decades, a wide range of crises has influenced the fates of cities and their inhabitants. When reviewing the first two decades of this century, we might feel that we are living in a “time of constant crises”; starting with the real estate and financial crisis in 2007/2008, a wide range of subsequent crises has spread all over the world: various economic, real estate, and bank crises, as well as the Euro debt crisis, which have led to political crises with significant social repercussions, also across Europe (Funke et al. 2015). In addition, a number of wars and violent conflicts such as, e.g., those in Syria and Northern Iraq have caused new crises; in particular, the increased refugee migration towards Europe (preferably to large cities of some European countries), an area that still has to cope with the consequences of the above-mentioned crises. Multiple environmental crises are receiving much less attention at the moment (Gawel 2014). These include biodiversity loss or climate change that evokes extreme events, such as floods or droughts that also regularly impact on cities or urban regions. Last but not least, the increasing demographic polarization of the world’s population, with population decrease and ageing in the developed countries and further population growth in the Global South, are perceived as a long-term crisis that is leading, e.g., to increasing south-north migration at a global scale. Given a situation of “multiple crises”, i.e., crises that differ in their nature but are characterized by many interlinkages concerning their roots and impacts, we can observe emerging crisis-driven policies. These policies vary according to the type of crisis: bank rescues and austerity policies to tackle the financial crisis, diplomacy and border closures to regulate the immigration crisis, massive international climate-protection agendas and meetings to address the climate crisis that are characterized by particular interests and symbolic declarations, and so on.

Combining tacit knowledge elicitation with the SilverKnETs tool and random forests – The example of residential housing choices in Leipzig

Residential choice behaviour is a complex process underpinned by both housing market restrictions and individual preferences, which are partly conscious and partly tacit knowledge. Due to several limitations, common survey methods cannot sufficiently tap into such tacit knowledge. Thus, this paper introduces an advanced knowledge elicitation process called SilverKnETs and combines it with data mining using random forests to elicit and operationalize this type of knowledge. For the application case of the city of Leipzig, Germany, our findings indicate that rent, location and type of housing form the three predictors strongly influencing the decision making in residential choices. Other explanatory variables appear to have a much lower influence. Random forests have proven to be a promising tool for the prediction of residential choices, although the design and scope of the study govern the explanatory power of these models.

Zimmer frei? Die Wiederentdeckung der Relevanz des studentischen Wohnens für lokale Wohnungsmärkte

ZusammenfassungAngesichts steigender Studierendenzahlen und zunehmender Wohnungsknappheit gewinnen Diskussionen über das Segment des studentischen Wohnens in Politik, Medien, Wohnungswirtschaft und Wissenschaft erneut an Aufmerksamkeit. Verlässliche und umfassende Informationen über die Märkte und Marktentwicklungen dienen in diesem Zusammenhang als wichtige Voraussetzung für sozialpolitische und wohnungswirtschaftliche Entscheidungen. Dabei wird deutlich, dass in Wissenschaft und Praxis nur geringe Kenntnisse über die aktuelle Entwicklung und Struktur des Segments und seinen Auswirkungen auf die lokalen Wohnungsmärkte vorhanden sind. Der Beitrag setzt an dieser Forschungslücke an. Für das Segment des studentischen Wohnens werden zunächst die Faktoren der steigenden Wohnungsnachfrage Studierender herausgearbeitet und Untersuchungen zum studentischen Wohnen im Hinblick auf ihre wohnungsmarktpolitische Bedeutung vorgestellt. Weiterhin werden die Entwicklung und Struktur der Angebots- und Nachfrageseite in ihrer jeweiligen Besonderheit charakterisiert und Kopplungseffekte mit dem lokalen Wohnungsmarkt abgeleitet. Vor dem Hintergrund der derzeitigen Diskussion um Wohnungsknappheit werden die Folgen der Marktbedingungen auf Mieter- und Vermietermärkten für Studierende herausgearbeitet sowie marktspezifische Handlungsansätze zur Erhöhung der Markttransparenz dargestellt.AbstractDue to the rising number of students and an increasing shortage in housing in many university cities, debates about student housing are starting to gain more attention from politics, the media, the housing industry and science. As a result, the state of knowledge about the structure and development of the local housing market and its impact is rather limited in both theory and practice. Reliable and comprehensive information about the housing market and its evolution are essential for socio-political and housing-related decisions. This paper aims at filling this research gap. After describing factors related to the rising demand in student housing, case studies focusing on student housing and its political significance are presented. Furthermore, this study characterises the development and structure of supply as well as the demand for student housing, and how these factors interrelate with the local housing market. In light of the current discussion about the housing shortages, the consequences of the rental market conditions for students are highlighted. Finally, this paper concludes by providing possible approaches to ensure market transparency