New York: A supertanker every 1.5 days

Resource consumption of the 27 largest megacities in the world for the first time in comparison

New York ranks first among the 27 largest megacities in resource consumption © rabbit75 / thinkstock
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New York is a real energy-hungry, Tokyo is surprisingly economical and London is the only megacity whose power consumption is even declining. How the 27 largest megacities of the earth deal with energy, water and other resources, an international research team has now for the first time comprehensively compared - with some amazing results. But they also show that the growing metropolitan areas disproportionately consume resources.

The major metropolitan areas of the world continue to grow: in 1970 there were only eight cities worldwide with more than ten million inhabitants, in 2010 there were already 27 such megacities - more than half of the world's population now lives in cities. But that has consequences. Because the metropolitan areas with their dense population consume enormous amounts of resources.

27 city giants in comparison

How many of these are actually Chris Kennedy of the University of Toronto and his colleagues have now for the first time in the 27 largest megacities studied in comparison. Among them are the world's largest conurbation Tokyo, Mexico City, Shanghai, Mumbai and Guangzhou, but also the US cities of New York and Los Angeles and major European cities such as London, Paris and Moscow.

Even the totals show how high the resource requirements of these giants are among the metropolitan areas: 6.7 percent of the world's population live in the 27 largest megacities. Yet their residents consume nine percent of the world's electricity and ten percent of the fuel. At the same time, they produce almost 13 percent of global waste.

Energy and water consumption of the 27 largest megacities © Kennedy et al./ PNAS

A supertanker every one and a half days

However, the comparison of the cities with each other showed clear differences. The frontrunner in the negative sense was New York in almost all categories: The US megacity consumed the most energy and water and produced almost three times as much waste as the next metropolis, Mexico City. New York's energy needs alone are equivalent to charging a supertanker every 1.5 days, Kennedy reports. "When I saw that, I thought that was incredible, " says the researcher. display

In total, nine megacities are among the super energy eaters: Moscow, Seoul, Los Angeles, Shanghai, Guangzhou, Osaka, Tehran, Mexico City and London consume more than 1, 000 petajoules a year, which is equivalent to about 280 gigawatt hours. In terms of water consumption, New York was 10.9 million megaliters ahead of Guangzhou and Shanghai at 9.8 and Los Angeles at 6.6 million megaliters. The least used Jakarta with only 0.48 million megalitres.

Wealth, density and location play a role

As a reason for the differences, the researchers mainly call the economy: "rich people consume more and ultimately throw away more stuff, " said Kennedy. "The average New Yorker consumes 24 times more energy than a resident of Jakarta and produces more than 15 times the waste." It is no coincidence that megacities such as Calcutta, Lagos or Delhi are in the bottom of the list of consumers.

However, the geographical location and density of urban settlements also play a role, as the researchers explain: cities located in cooler regions also consume more energy because they heat more in winter need. Examples of this are New York and Moscow. In addition, "Least dense cities like Los Angeles and New York have more living space per capita, " the researchers said. "That leads to higher power consumption through heating, lighting and other applications."

The world's largest megacity Tokyo is at least in water consumption in a positive example free images

There is another way

But wealth and location do not explain all differences, as the researchers emphasize. The comparison also reveals that some cities are actively and successfully working to reduce their resource use while others are not. The 34-million city of Tokyo has reduced energy consumption from traffic through its effective public transport system. Targeted measures also ensured that the loss of water through leaks in the piping system was reduced to just three percent.

Seoul is also a positive example: The city has developed and installed a system for the secondary use of domestic water, for example, for toilet flushing. As a result, the resource water is used more effectively. Counter examples are the South American metropolises of Rio de Janeiro and Sao Paulo: Here, more than 50 percent of the water seeps unused into the ground. "These are places that are actually very close to water but they let it seep away, " says Kennedy.

The resource eaters are growing rapidly

And the development continues, because the megacities are growing rapidly, as the researchers report. In the ten years from 200 to 2010, half of the 27 megacities surveyed grew by more than ten percent, while Istanbul, Dhaka, Beijing, Shenzhen and Shanghai even grew by more than 40 percent. As the population grows, so does the demand for resources - and for the most part, even disproportionately fast. In nine of the megacities power consumption increased three times more than the population.

The exception here is London: The British capital is the only one among the megacities whose power consumption declined despite rising population. This was achieved, among other things, by a 66 percent increase in the price of electricity and increased energy efficiency in buildings and equipment, the researchers report.

"It shows that megacities can make progress in reducing their resource use, " said Kennedy. "That's encouraging." The study also shows that there is an urgent need for action. (Proceedings of the National Academy of Sciences (PNAS), 2015; doi: 10.1073 / pnas.1504315112)

(University of Toronto, 29.04.2015 - NPO)