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  - Rybski, Diego
A1  - Reusser, Dominik Edwin
A1  - Winz, Anna-Lena
A1  - Fichtner, Christina
A1  - Sterzel, Till
A1  - Kropp, Jürgen
T1  - Cities as nuclei of sustainability?
JF  - Environment and Planning B: Urban Analytics and City Science
N2  - We have assembled CO2 emission figures from collections of urban GHG emission estimates published in peer-reviewed journals or reports from research institutes and non-governmental organizations. Analyzing the scaling with population size, we find that the exponent is development dependent with a transition from super- to sub-linear scaling. From the climate change mitigation point of view, the results suggest that urbanization is desirable in developed countries. Further, we compare this analysis with a second scaling relation, namely the fundamental allometry between city population and area, and propose that density might be a decisive quantity too. Last, we derive the theoretical country-wide urban emissions by integration and obtain a dependence on the size of the largest city.
KW  - Scaling
KW  - cities
KW  - climate change
KW  - development process
KW  - allometry
Y1  - 2017
U6  - https://doi.org/10.1177/0265813516638340
SN  - 2399-8083
SN  - 2399-8091
VL  - 44
IS  - 3
SP  - 425
EP  - 440
PB  - Sage Publ.
CY  - London
ER  -