TY - JOUR A1 - Pradhan, Prajal A1 - Kriewald, Steffen A1 - Costa, Luís Fílípe Carvalho da A1 - Rybski, Diego A1 - Benton, Tim G. A1 - Fischer, Günther A1 - Kropp, Jürgen T1 - Urban food systems: how regionalization can contribute to climate change mitigation JF - Environmental science & technology N2 - Cities will play a key role in the grand challenge of nourishing a growing global population, because, due to their population density, they set the demand. To ensure that food systems are sustainable, as well as nourishing, one solution often suggested is to shorten their supply chains toward a regional rather than a global basis. While such regional systems may have a range of costs and benefits, we investigate the mitigation potential of regionalized urban food systems by examining the greenhouse gas emissions associated with food transport. Using data on food consumption for 7108 urban administrative units (UAUs), we simulate total transport emissions for both regionalized and globalized supply chains. In regionalized systems, the UAUs' demands are fulfilled by peripheral food production, whereas to simulate global supply chains, food demand is met from an international pool (where the origin can be any location globally). We estimate that regionalized systems could reduce current emissions from food transport. However, because longer supply chains benefit from maximizing comparative advantage, this emission reduction would require closing yield gaps, reducing food waste, shifting toward diversified farming, and consuming seasonal produce. Regionalization of food systems will be an essential component to limit global warming to well below 2 degrees C in the future. Y1 - 2020 U6 - https://doi.org/10.1021/acs.est.0c02739 SN - 0013-936X SN - 1520-5851 VL - 54 IS - 17 SP - 10551 EP - 10560 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Fluschnik, Till A1 - Kriewald, Steffen A1 - Ros, Anselmo Garcia Cantu A1 - Zhou, Bin A1 - Reusser, Dominik Edwin A1 - Kropp, Jürgen A1 - Rybski, Diego T1 - The Size Distribution, Scaling Properties and Spatial Organization of Urban Clusters: A Global and Regional Percolation Perspective JF - ISPRS International Journal of Geo-Information N2 - Human development has far-reaching impacts on the surface of the globe. The transformation of natural land cover occurs in different forms, and urban growth is one of the most eminent transformative processes. We analyze global land cover data and extract cities as defined by maximally connected urban clusters. The analysis of the city size distribution for all cities on the globe confirms Zipf’s law. Moreover, by investigating the percolation properties of the clustering of urban areas we assess the closeness to criticality for various countries. At the critical thresholds, the urban land cover of the countries undergoes a transition from separated clusters to a gigantic component on the country scale. We study the Zipf-exponents as a function of the closeness to percolation and find a systematic dependence, which could be the reason for deviating exponents reported in the literature. Moreover, we investigate the average size of the clusters as a function of the proximity to percolation and find country specific behavior. By relating the standard deviation and the average of cluster sizes—analogous to Taylor’s law—we suggest an alternative way to identify the percolation transition. We calculate spatial correlations of the urban land cover and find long-range correlations. Finally, by relating the areas of cities with population figures we address the global aspect of the allometry of cities, finding an exponent δ ≈ 0.85, i.e., large cities have lower densities. Y1 - 2016 U6 - https://doi.org/10.3390/ijgi5070110 SN - 2220-9964 VL - 5 SP - 1543 EP - 1559 PB - MDPI CY - Basel ER - TY - JOUR A1 - Zhou, Bin A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - The role of city size and urban form in the surface urban heat island JF - Scientific reports N2 - Urban climate is determined by a variety of factors, whose knowledge can help to attenuate heat stress in the context of ongoing urbanization and climate change. We study the influence of city size and urban form on the Urban Heat Island (UHI) phenomenon in Europe and find a complex interplay between UHI intensity and city size, fractality, and anisometry. Due to correlations among these urban factors, interactions in the multi-linear regression need to be taken into account. We find that among the largest 5,000 cities, the UHI intensity increases with the logarithm of the city size and with the fractal dimension, but decreases with the logarithm of the anisometry. Typically, the size has the strongest influence, followed by the compactness, and the smallest is the influence of the degree to which the cities stretch. Accordingly, from the point of view of UHI alleviation, small, disperse, and stretched cities are preferable. However, such recommendations need to be balanced against e.g. positive agglomeration effects of large cities. Therefore, trade-offs must be made regarding local and global aims. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-04242-2 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Gudipudi, Venkata Ramana A1 - Rybski, Diego A1 - Lüdeke, Matthias K. B. A1 - Zhou, Bin A1 - Liu, Zhu A1 - Kropp, Jürgen T1 - The efficient, the intensive, and the productive BT - Insights from urban Kaya scaling JF - Applied Energy N2 - Urban areas play an unprecedented role in potentially mitigating climate change and supporting sustainable development. In light of the rapid urbanisation in many parts on the globe, it is crucial to understand the relationship between settlement size and CO2 emission efficiency of cities. Recent literature on urban scaling properties of emissions as a function of population size has led to contradictory results and more importantly, lacked an in-depth investigation of the essential factors and causes explaining such scaling properties. Therefore, in analogy to the well-established Kaya Identity, we develop a relation combining the involved exponents. We demonstrate that application of this Urban Kaya Relation will enable a comprehensive understanding about the intrinsic factors determining emission efficiencies in large cities by applying it to a global dataset of 61 cities. Contrary to traditional urban scaling studies which use Ordinary Least Squares (OLS) regression, we show that the Reduced Major Axis (RMA) is necessary when complex relations among scaling exponents are to be investigated. RMA is given by the geometric mean of the two OLS slopes obtained by interchanging the dependent and independent variable. We discuss the potential of the Urban Kaya Relation in mainstreaming local actions for climate change mitigation. KW - Sustainable cities KW - Urban CO2 emissions KW - Urban scaling KW - Kaya Identity KW - Urban Kaya relation Y1 - 2018 U6 - https://doi.org/10.1016/j.apenergy.2018.11.054 SN - 0306-2619 SN - 1872-9118 VL - 236 SP - 155 EP - 162 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Li, Yunfei A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - Singularity cities JF - Environment and planning. B, Urban analytics and city science N2 - We propose an upgraded gravitational model which provides population counts beyond the binary (urban/non-urban) city simulations. Numerically studying the model output, we find that the radial population density gradients follow power-laws where the exponent is related to the preset gravity exponent gamma. Similarly, the urban fraction decays exponentially, again determined by gamma. The population density gradient can be related to radial fractality and it turns out that the typical exponents imply that cities are basically zero-dimensional. Increasing the gravity exponent leads to extreme compactness and the loss of radial symmetry. We study the shape of the major central cluster by means of another three fractal dimensions and find that overall its fractality is dominated by the size and the influence of gamma is minor. The fundamental allometry, between population and area of the major central cluster, is related to the gravity exponent but restricted to the case of higher densities in large cities. We argue that cities are shaped by power-law proximity. We complement the numerical analysis by economics arguments employing travel costs as well as housing rent determined by supply and demand. Our work contributes to the understanding of gravitational effects, radial gradients, and urban morphology. The model allows to generate and investigate city structures under laboratory conditions. KW - Gravity models KW - population density KW - urban fraction KW - fractal geometry Y1 - 2021 U6 - https://doi.org/10.1177/2399808319843534 SN - 2399-8083 SN - 2399-8091 VL - 48 IS - 1 SP - 43 EP - 59 PB - Sage Publ. CY - London ER - TY - JOUR A1 - Boettle, Markus A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - Quantifying the effect of sea level rise and flood defence-a point process perspective on coastal flood damage JF - Natural hazards and earth system sciences N2 - In contrast to recent advances in projecting sea levels, estimations about the economic impact of sea level rise are vague. Nonetheless, they are of great importance for policy making with regard to adaptation and greenhouse-gas mitigation. Since the damage is mainly caused by extreme events, we propose a stochastic framework to estimate the monetary losses from coastal floods in a confined region. For this purpose, we follow a Peak-over-Threshold approach employing a Poisson point process and the Generalised Pareto Distribution. By considering the effect of sea level rise as well as potential adaptation scenarios on the involved parameters, we are able to study the development of the annual damage. An application to the city of Copenhagen shows that a doubling of losses can be expected from a mean sea level increase of only 11 cm. In general, we find that for varying parameters the expected losses can be well approximated by one of three analytical expressions depending on the extreme value parameters. These findings reveal the complex interplay of the involved parameters and allow conclusions of fundamental relevance. For instance, we show that the damage typically increases faster than the sea level rise itself. This in turn can be of great importance for the assessment of sea level rise impacts on the global scale. Our results are accompanied by an assessment of uncertainty, which reflects the stochastic nature of extreme events. While the absolute value of uncertainty about the flood damage increases with rising mean sea levels, we find that it decreases in relation to the expected damage. Y1 - 2016 U6 - https://doi.org/10.5194/nhess-16-559-2016 SN - 1561-8633 VL - 16 SP - 559 EP - 576 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Zhou, Bin A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - On the statistics of urban heat island intensity JF - Geophysical research letters N2 - We perform a systematic study of all cities in Europe to assess the Urban Heat Island (UHI) intensity by means of remotely sensed land surface temperature data. Defining cities as spatial clusters of urban land cover, we investigate the relationships of the UHI intensity, with the cluster size and the temperature of the surroundings. Our results show that in Europe, the UHI intensity in summer has a strong correlation with the cluster size, which can be well fitted by an empirical sigmoid model. Furthermore, we find a novel seasonality of the UHI intensity for individual clusters in the form of hysteresis-like curves. We characterize the shape and identify apparent regional patterns. Y1 - 2013 U6 - https://doi.org/10.1002/2013GL057320 SN - 0094-8276 SN - 1944-8007 VL - 40 IS - 20 SP - 5486 EP - 5491 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Böttle, Markus A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - How changing sea level extremes and protection measures alter coastal flood damages JF - Water resources research N2 - While sea level rise is one of the most likely consequences of climate change, the provoked costs remain highly uncertain. Based on a block-maxima approach, we provide a stochastic framework to estimate the increase of expected damages with sea level rise as well as with meteorological changes and demonstrate the application to two case studies. In addition, the uncertainty of the damage estimations due to the stochastic nature of extreme events is studied. Starting with the probability distribution of extreme flood levels, we calculate the distribution of implied damages in a specific region employing stage-damage functions. Universal relations of the expected damages and their standard deviation, which demonstrate the importance of the shape of the damage function, are provided. We also calculate how flood protection reduces the damages leading to a more complex picture, where the extreme value behavior plays a fundamental role. Citation: Boettle, M., D. Rybski, and J. P. Kropp (2013), How changing sea level extremes and protection measures alter coastal flood damages, Water Resour. Res., 49, 1199-1210, doi: 10.1002/wrcr.20108. Y1 - 2013 U6 - https://doi.org/10.1002/wrcr.20108 SN - 0043-1397 VL - 49 IS - 3 SP - 1199 EP - 1210 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Hic, Ceren A1 - Pradhan, Prajal A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - Food Surplus and Its Climate Burdens JF - Geological Society of America bulletin N2 - Avoiding food loss and waste may counteract the increasing food demand and reduce greenhouse gas (GHG) emissions from the agricultural sector. This is crucial because of limited options available to increase food production. In the year 2010, food availability was 20% higher than was required on a global scale. Thus, a more sustainable food production and adjusted consumption would have positive environmental effects. This study provides a systematic approach to estimate consumer level food waste on a country scale and globally, based on food availability and requirements. The food requirement estimation considers demographic development, body weights, and physical activity levels. Surplus between food availability and requirements of a given country is considered as food waste. The global food requirement changed from 2,300 kcal/cap/day to 2,400 kcal/cap/day during the last 50 years, while food surplus grew from 310 kcal/cap/day to 510 kcal/cap/day. Similarly, GHG emissions related to the food surplus increased from 130 Mt CO2eq/yr to 530 Mt CO2eq/yr, an increase of more than 300%. Moreover, the global food surplus may increase up to 850 kcal/cap/day, while the total food requirement will increase only by 2%-20% by 2050. Consequently, GHG emissions associated with the food waste may also increase tremendously to 1.9-2.5 Gt CO2eq/yr. Y1 - 2016 U6 - https://doi.org/10.1021/acs.est.5b05088 SN - 0013-936X SN - 1520-5851 VL - 50 SP - 4269 EP - 4277 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ribeiro, Haroldo V. A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - Effects of changing population or density on urban carbon dioxide emissions JF - Nature Communications N2 - The question of whether urbanization contributes to increasing carbon dioxide emissions has been mainly investigated via scaling relationships with population or population density. However, these approaches overlook the correlations between population and area, and ignore possible interactions between these quantities. Here, we propose a generalized framework that simultaneously considers the effects of population and area along with possible interactions between these urban metrics. Our results significantly improve the description of emissions and reveal the coupled role between population and density on emissions. These models show that variations in emissions associated with proportionate changes in population or density may not only depend on the magnitude of these changes but also on the initial values of these quantities. For US areas, the larger the city, the higher is the impact of changing its population or density on its emissions; but population changes always have a greater effect on emissions than population density. Y1 - 2019 U6 - https://doi.org/10.1038/s41467-019-11184-y SN - 2041-1723 VL - 10 PB - Nature Publ. Group CY - London ER -