In the near future, cities will be the stages on which we address the world’s most pressing problems. Waste-management, while it may seem boring, is near the top of that list.

Waste is a huge problem in megacities, which are cities loosely defined as having over 10 million residents. The rapid rate of urbanization has exacerbated waste management in big cities, and, according to a report by the United Nations, their public waste systems often can’t keep up with their sprawling growth.

“The more urbanized and industrialized a country becomes, the more trash it produces,” said Ijjasz-Vasquez, a senior director for the World Bank's Social, Urban, Rural and Resilience Global Practice.

Moreover, improperly handled waste accelerates the spread of disease and often runs-off into waterways, polluting the environment. The impacts of this pollution disproportionately affect the poor.

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The city reportedly wastes 14 million tonnes of trash each year. To handle that, much of the waste is exported overseas to China; in fact, trash is the U.S.’s number one export to China.

New York, the largest city in the world’s most wasteful country, hasn’t neatly solved the escalating problem of trash. And, in the city itself, illegal dumping is still a problem.

After New York, Mexico City ranks as the second highest urban waster. The city wastes 12 million tonnes per year, closely followed by Tokyo, Los Angeles and Mumbai. After that come Istanbul, Jakarta, and Cairo, the last of which has its own garbage city.

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Whereas New York and Tokyo were once the only two megacities in the 20th century, the world will have forty-five such sprawling metropolises as a result of big urban migrations. These cities will host up to two-thirds of the world by 2030, according to the UN.

How these cities pivot to solve 21st centuries problems of waste will be critical. The world’s 27 megacities produce 12% of global waste, according to a PNAS study from 2015.

And the problem is only growing, says Vasquez, who expects the world’s annual trash production to reach 4 billion tonnes by the year 2100. That’s up from the 1.3 billion tonnes produced today, he told the LA Times.

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With such a daunting increase, it makes sense to focus on the huge cities that produce a disproportionate amount of trash: 13% of the world’s solid waste, relative to about 7% of global population.

So far, cities haven’t adequately responded to this reality. For example, in Beijing and other Chinese metropolises, recycling programs have become an ineffective for-profit industry, resulting in trash growing at twice the rate of its population, as per The Guardian.

And New York City should really be doing better than Tokyo, whose lower waste levels are a product of aggressive policy, despite having over twice as many residents.

Today, 54% of the world’s population lives in urban areas. As that percentage grows, city governments will need to throw their weight into innovative waste-management rather than simply ship the problem out of sight.