The Growth and Decline of Urban Agglomerations in Germany

Innovative maps that illustrate the most recent socio-demographic urban changes in the major city urban agglomerations in Germany have very recently been produced in a joint project of the School of Geography and the Environment at the University of Oxford and the Research Institute for Regional and Urban Development Dortmund (Germany).
The Research Institute for Regional and Urban Development (Institut für Landes und Stadtentwicklungsforschung, ILS) investigates new social processes, especially those involving urbanisation in Germany and Europe. This includes economic, social and structural processes that are compared and monitored over time to gain a better understanding of the underlying developments. Testing state-of-the-art visualisation techniques are a significant part of this effort. This was the focus of a collaboration between researchers of the University of Oxford and the ILS Dortmund which resulted in the development of a series of highly effective maps called “cartograms” that provide new insights in the changing geographies of city regions in Germany.

Mapping the Growth and Decline of Urban Agglomerations in Germany
(click for larger version)

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Urbane Veränderungsprozesse in Stadtregionen Deutschlands

This is a German-language poster contribution looking at processes of change in the major urban agglomerations in Germany and novel ways of visualising these using cartogram visualisation techniques. Continue reading

The Pearl River Delta: A City of Cities

Earlier this year the British Telegraph Newspaper published a story about the creation of a new megacity in the Chinese Pearl River delta region. “China is planning to create the world’s biggest mega city by merging nine cities to create a metropolis twice the size of Wales with a population of 42 million”, the opener of their story stated. The region mentioned here is an area covering the cities of Guangzhou, Shenzhen, Donggaun, Foshan, Huizhou, Zhaoqing, Jiangmen, Zhongshan and Zhuhai (as described in the China Urban Development Blog). The story was quickly picked up by many news sources back then, while Chinese officials were quick to deny the reports. Stories like this show, how urbanisation and megacities have become a buzz word, and are used especially in relation to the emerging economies in Asia in order to picture these – for western-centric eyes unbelievably – large and still growing populations in the most urbanised regions on the planet. A few thoughts on the relevance of megacities in their global context have been published on this website before (related to the map of the world’s megacities).
With special regard to the Telegraph story I have drawn another map showing the population distribution of China (based on 2010 Data from the Chinese Census and from estimates of SEDAC’s GPW database) and highlighted the Pearl River Delta region in this map. The equal-population map shows a gridded population cartogram in which every grid cell is resized according to the total number of people living there. This map makes the plans of a more integrated Pearl River Delta region more understandable, and perhaps slightly less exciting for those who interpreted the news as the creation of a new megacity, rather than the logical step in connecting an already populous region.

Map / Gridded Population Cartogram of China and the Pearl River Delta
(click for larger map)

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Megacities on the Map

Megacities are major global risk areas. Due to highest concentration of people and extreme dynamics, they are particularly prone to supply crises, social disorganization, political conflicts and natural disasters. Their vulnerability can be high.

This quote from the IGU’s MegaCity TaskForce draws a quite bleak picture of what some believe to be the future of living for humankind. The UN World Urbanisation Prospects finally saw the urban populations surpassing rural living for the first time in human history in recent years, but we must not forget that these urban populations do not all live in what is referred to as a megacity.
A megacity basically is nothing more than a very large city. Widely used is a population of 10 million, but other definitions do exist, ranging from 5 or 8 million, and some people, such as German geographer Bronger are also including the population density of 2000 p. per sq km as a defining factor). The definition of a megacity should also be seen as a rather vague delimitation for a phenomenon that – despite it’s quantitative dimension – has a very qualitative nature: What happens, when extremely large numbers of people live in a very limited amount of space, and what happens, if these areas of very high density living even continue growing.
In the year 2000 there were 39 cities with a population of more than 5 million inhabitants, 2/3 of which were in the developing countries. This was a population of 225 million people, not even 5% of the world’s population. Today we have about 400 million people living in the largest cities on the planet – still far from the majority of the now more than half of the world’s population living in cities. And perhaps the majority of people on this planet may never live in one of these megacities. Why is everyone talking about megacities then anyway? The sheer size make these cities the ultimate examples for urbanization, and provide an insight to the diverse processes in such complex urban spaces. They are like a real-life laboratory for urban geographers who try to understand the impact and implications of urbanization processes, and may contribute to solutions how the urban future of humanity can be actively created and lead to a better and perhaps more sustainable life on this planet.
A gridded population cartogram can help to understand not only the locations of these largest of cities, but provides a look into their setting within the global population patterns by giving space to people and allowing to see where many people live in these large cities, and where people are in relation to these cities. A normal map (see further down) shows the high concentration of megacities especially in Asia, but we can see from the population cartogram that these are in those anyway very densely populated regions, while the megacities in South America appear more like (relatively seen) solitary bodies.

Cartogram / Map of the World's Megacities in 2015
(click for larger map)

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Urban development in the city of Cologne (Köln)

Mapping Cologne
In a previous post on this website I looked at urban mapping showing population changes in London. This time I dug up a different example for mapping cities from my map archive: The German city of Cologne (Köln) is one of Germany’s largest cities with a total population of approximately 1 million people. It its over 2000 years lasting history, its urban landscape changed considerably, and since the Prussian times in the 19th century fairly good mapping records cover the modern land use change from the pre-industrialised to the post-modern city. In a GIS mapping project some years ago, these changes have been digitized in full detail from some major topographic maps, covering the changes in the urban land use since 1850 (see bottom image of this page for the legend to this animation):

Map animation of the Land Use Change in the German city of Cologne / Köln

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Megacities and Earthquake Risk

Read more about this map:
Paper in the Journal of Maps: Gridded cartograms as a method for visualising earthquake risk at the global scale

The following map is a modified version of the earthquake vulnerability map published on this website last month (see that page for more details on the underlying earthquake map). The map itself does not show much new information, but includes an aditional layer containing the largest cities of the world, the so-called megacities (depending on the definition, these are cities with a population of more than 5, 8 or 10 million). The circles reflect the category in which each city belongs (based on 2015 estimations by the UN), and they are placed on the location of the city related to the total population distribution. As the map is resized according to the population (equal-population projection), the map also help to understand the setting of each city within the global population density, explaining why the artificial boundaries of a city do not always tell the full story of the urban population structure within a region. In some areas, such as Hong Kong and Guangzhou in the Pearl River Delta, cities are just one of several centres in a highly urbanised region – an urban sprawl – while other megacities like Mexico City or Moscow are in a more solitary location (although even here the extent of the populated area goes beyond the urban boundaries, and certainly the population is far from solitude). Without the city labels the map already showed the relation between human settlements and earthquake risk. The following map now allows to better understand the underlying geography if one is not so familiar with that kind of map transformation.
On a more technical note, the following map feature also includes another jQuery feature (I experimented with the image slider applied to maps on the earth at night map): This map uses the Zoomy Plugin to reveal a more detailed version of the map using an interactive magnifier. Click on the map map to enable the magnifier and see more detail (or if you don’t like that, click here for the usual large version of the map).

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