Nina Schwarz

A quantitative review of urban ecosystem service assessments: concepts, models, and implementation.

Although a number of comprehensive reviews have examined global ecosystem services (ES), few have focused on studies that assess urban ecosystem services (UES). Given that more than half of the world’s population lives in cities, understanding the dualism of the provision of and need for UES is of critical importance. Which UES are the focus of research, and what types of urban land use are examined? Are models or decision support systems used to assess the provision of UES? Are trade-offs considered? Do studies of UES engage stakeholders? To address these questions, we analyzed 217 papers derived from an ISI Web of Knowledge search using a set of standardized criteria. The results indicate that most UES studies have been undertaken in Europe, North America, and China, at city scale. Assessment methods involve bio-physical models, Geographical Information Systems, and valuation, but few study findings have been implemented as land use policy.

An integrated modelling framework for simulating regional-scale actor responses to global change in the water domain

Within coupled hydrological simulation systems, taking socio-economic processes into account is still a challenging task. In particular, systems that aim at evaluating impacts of climatic change on large spatial and temporal scales cannot be based on the assumption that infrastructure, economy, demography and other human factors remain constant while physical boundary conditions change. Therefore, any meaningful simulation of possible future scenarios needs to enable socio-economic systems to react and to adapt to climatic changes. To achieve this it is necessary to simulate decision-making processes of the relevant actors in a way which is adequate for the scale, the catchment specific management problems to be investigated and finally the data availability. This contribution presents the DeepActor approach for representing such human decision processes, which makes use of a multi-actor simulation framework and has similarities to agent-based approaches. This DeepActor approach is embedded in Danubia, a coupled simulation system comprising 16 individual models to simulate Global Change impacts on the entire water cycle of the Upper Danube Catchment (Germany, 77,000km^2). The applicability of Danubia and in particular the DeepActor approach for treating the socio-economic part of the water cycle in a process-based way is demonstrated by means of concrete simulation models of the water supply sector and of the domestic water users. Results from scenario simulations are used to demonstrate the capabilities and limitations of the approach.

Omnipresent Sprawl? A Review of Urban Simulation Models with Respect to Urban Shrinkage

Simulation models on urban land-use change help in understanding urban systems and assist in urban planning. One of the challenges of simulating urban regions in Europe as well as in North America or Japan is urban shrinkage, where deindustrialisation, massive population losses, and ageing cause unforeseen (or unexpected) commercial and housing vacancies in cities. In order to set up a conceptual framework for model improvement to assist such challenges, we review recent urban land-use-change simulation models, using four different modelling approaches: system dynamics, linked transport — urban models, cellular automata, and agent-based modelling. The focus of the review is to assess the causalities and feedback mechanisms that were implemented in these models. The results show that simulation models are very heterogeneous in implemented mechanisms leading to urban land-use dynamics. No single model fulfils all of the criteria required to model urban shrinkage in a spatially explicit way. However, system-dynamic models that are documented in the literature can serve as a good starting point for spatially nonexplicit simulation, and one example was found for linked transport — urban models which encompasses aspects of urban shrinkage. The potential of cellular automata is unclear as spatially explicit data on vacancies to feed this class of models is usually not available. Agent-based models appear to be the most promising approach for spatially explicit modelling of urban shrinkage.

Simulating Demography and Housing Demand in an Urban Region under Scenarios of Growth and Shrinkage

After the fall of the Berlin wall in 1989, demographic decline and urban shrinkage brought massive changes in the housing stock in East German cities. Urban planners and policy makers face complex problems caused by the resulting vacancies and demolitions and the handling of urban brownfields in the inner city. At the same time, cities are under ongoing pressure of suburbanisation. Because existing models focus mainly on demographic and urban growth and their impact on housing stocks, we present a simulation model that is able to compute both growth and shrinkage processes. We uncover nonlinear dynamics and feedbacks between demography, housing preference, and supply of housing space. The simulation results show that, despite population decline, the increasing number of single households leads to a growing total housing demand in the central parts of the study area. Beyond this area, residential vacancies in multistorey housing segments will remain regardless of population growth. At the same time, the simulations show that, despite population shrinkage and an overall oversupply of flats, there is a negative net demand for flats in affordable prefabricated housing estates as the percentage of low-income households increases. These findings will help planners modify or adapt their visions of the residential function in shrinking cities and to adjust current programmes of renewal and restructuring.

The bigger, the better? The influence of urban green space design on cooling effects for residential areas

It is well known that the cooling effect of an urban green space extends into its surroundings, cooling the immediate environment and mitigating urban heat problems. However, the effects of size, shape, and type of an urban green space on cooling remain uncertain. The objectives of our study were to quantify and compare the strength of the cooling effects of urban parks and forests, to determine how far the cooling effects extend into the surrounding residential environment, and to better understand how temperature gradients are driven by physical characteristics of the green space and the surroundings. Mobile air temperature measurements were performed in 62 urban parks and forests in the city of Leipzig, Germany, in the summer of 2013. Three indicators of cooling were calculated: the change in temperature (ΔT) at the park-width distance, the maximum ΔT, and the cooling distance. The relationships of these variables to the physical characteristics of the green spaces and their surroundings were examined in multiple regression models. Analyzing all three indicators revealed that cooling effects were greater in urban forests than in parks. Cooling increased with increasing size but in a different manner for forests and parks, whereas the influence of shape was the same for forests and parks. Generally, the characteristics of the green spaces were more important than the characteristics of the residential surroundings. These findings have the potential to assist in better planning and designing of urban green spaces to increase their cooling effects.

Soziale Dimensionen von Hitzebelastung in Grossstädten

Increasing heat stress is one of the impacts of global warming cities have to cope with and adapt to. The recent German and international debate focuses on the threat of increasing mortality rates, especially the vulnerability of the elderly people and measures to reduce it. Further, possibilities of adaptation to climate change by means of urban design to reduce the urban heat island effect are investigated. Little is known so far about the subjective perception of heat stress of different social and demographic groups, about how heat stress interferes with everyday life conduction of the inhabitants of cities, about subjective adaptation strategies and thus, about the interrelation of heat stress and the organization of the urban society. Building on two recent exploratory studies, the paper shows what other dimensions of heat stress are relevant too. The results give rise to a number of hypotheses on the social dimensions of heat stress that have to be further investigated. English Title: Social dismensions of heat-stress in cities.

Modelling the impacts of urban upgrading on population dynamics

Due to the rapid pace of urbanization, cities in the global South are growing with most of this growth occurring in informal settlements. Urban upgrading aims to improve living conditions in such settlements by improving the infrastructure but might lead to unexpected effects such as income segregation. InformalCity, a spatially explicit agent-based model, simulates the implications of urban upgrading in an artificial city. Our simulation experiments show that maintenance of the upgraded infrastructure, the scope of upgrading efforts, and timing (early vs. late investments) affect infrastructure quality, housing development and income segregation. However, we also find that urban upgrading interventions can have contradictory effects; for example, maintenance increases the quality of infrastructure and income segregation. Thus, policy makers need to establish clear targets for upgrading projects, and empirical evaluation studies should consider studying the impacts of urban upgrading on an entire citys development rather than limiting them to informal settlements. We model urban upgrading of informal settlements in an agent-based model (ABM).ABM allows evaluating impacts of upgrading on living conditions in the whole city.City-wide evaluation is a significant improvement over traditional approaches.Five configuration parameters for urban upgrading were distinguished.Upgrading has contradictory effects on infrastructure quality and segregation.

Leipzig-Halle : Ecosystem Services in a Stagnating Urban Region in Eastern Germany

Land use change makes an impact on ecosystem services and quality of life in urban regions. The dynamics of land use change as well as their effects are more clearly understood by taking local conditions into account. In the case of Leipzig-Halle, a period of heavy commercial and residential suburbanisation has recently come to an end. With uneven economic and population development, the region is characterised by stagnation and internal disparities. A clear-cut future development path is not self-evident. This raises questions for regional decision makers, planners and scientists alike: What are the potential land use developments of the future? Which of them are desirable and which are not? What, therefore, are appropriate and effective steering options? These questions are examined in this chapter.

Tools for Modelling and Assessing Peri-Urban Land Use Futures

Chapters 1 and 2 set the scene for the scenarios of possible futures, presented modelling results and identified a typology of rural urban regions. The next set of chapters in Part 2 focus on the case studies and what can be learned from them. Before examining each case study it will be useful to provide an overview of the various models and tools used to simulate potential land use futures of peri-urban regions and to assess their impacts across Europe. The focus of this chapter is at two scales: the pan-European (EU27) and the regional scale, as produced by the typology in Chap. 2 and exemplified by the case studies presented in Chaps. 4, 5, 6, 7, 8 and 9.

Describing Human Decisions in Agent-Based Social-Ecological Models - ODD+D an Extension of the ODD Protocol

Multiple agent-based models (ABM) on social-ecological systems exist in parallel investigating similar research questions. However, the choice of a particular human decision model is often not sufficiently empirically or theoretically substantiated in the model documentation. Furthermore, model comparison is difficult because model descriptions are often incomplete, intransparent and difficult to understand. Therefore we expand and refine the ‘ODD’ (Overview, Design Concepts, and Details) protocol to establish a standard to describe ABMs which includes human decision making (ODD+D). Since the original ODD is mainly from an ecological perspective, some adaptations are necessary for the social-ecological context. We extended and rearranged the design concepts and related guiding questions to differentiate and describe decision making, adaptation and learning of the agents in a comprehensive and clearly structured way. Furthermore, ODD+D encompasses a section on ‘Theoretical and empirical background’ to encourage that model design and model assumptions are related more closely to theory. The application of ODD+D is illustrated with a description of a social-ecological ABM on water use. We believe that our expansions help to make the ODD protocol a most suitable protocol to describe social-ecological ABMs and may support the review process of related manuscripts. The ODD+D protocol does not only improve the quality of model descriptions but also improves our understanding of models and is an important necessary step forward developing theory respectively frameworks for social-ecological ABMs.