It’s the stereotype we’re all aware of – rich cities with sparkling streets and sidewalks, and poorer cities with rubbish piling up and dirty, congested roads.
But how true is this really? A study published in Nature Cities has found that cities with a higher per-capita GDP create more waste overall.
“We as a society tend to ignore the unpleasant side of our production,” says Mingzhen Lu, an assistant professor in environment at New York University.
And with almost two-thirds of the world’s population to live in cities by 2050, we need to be better aware of our own waste.
The researchers looked at three forms of waste – water use, garbage, and greenhouse gasses.
They examined more than 1,000 cities across the world, ranging from 50,000 to 24 million people in size. The researchers highlighted Chinese cities especially because they are a good example of rapid urbanisation where there is plenty of data.
They found that as the cities scale up, not everything gets more efficient. Garbage – or solid waste – scales upwards linearly. But wastewater production scales faster than what would be added for each person. The researchers aren’t sure why this is but suggest that wealth creation and water consumption might be tightly linked – for example in some industry settings.
Finally, greenhouse gases went in the other direction. If a city doubles in size, greenhouse gas emissions don’t double with it.
The team suggests that this means that bigger cities are more energy efficient but less water efficient.
More importantly, they showed that cities with a higher per-capita GDP generated more waste.
“Increases in GDP often improve the quality of life for individuals in cities, so we need ways to decouple the link between increasing economic prosperity and per capita waste production,” the researchers write in their paper.
“Perhaps we can look to San Francisco or Japanese cities as examples of high GDP and low waste cities.
“The structural features, cultural dynamics, and policies that allow these cities to reduce waste need to be more systematically understood in connection with scaling and deployed in most global cities.”