Currently, over 80 percent of the global population resides in urban areas, a statistic that’s on the rise, emphasizing the necessity for cities to enhance both human health and environmental sustainability, as detailed in a significant United Nations report.

The latest Outlook for Global Urbanization report, published in 2018, indicated that 55 percent of the population lived in urban settings. However, these estimates vary internationally based on disparate definitions of urban and rural regions. For instance, Denmark considers an urban settlement to be one with a population of about 200, while Japan sets the threshold at 50,000, obscuring the understanding of global urbanization.

To clarify matters, Sarah Hertog, a researcher for the United Nations in New York, identified urban areas as those with at least 50,000 inhabitants and a density of 1,500 people per square kilometer, or cities with a minimum of 5,000 people and 300 people per square kilometer.² “For the first time, we applied a consistent definition across all countries,” Hertog stated.

The researchers analyzed satellite and national survey data from 237 nations and territories to project global urbanization trends for 2025. Their findings indicated that 45 percent of the world’s population currently resides in cities, most within urban areas of fewer than 250,000 inhabitants, meaning a total of 81 percent of people are urban residents, with the last 19 percent in rural regions.

Statistical models incorporating factors like aging and migration patterns predict that by 2050, 83 percent of the global population will inhabit cities rather than rural settings. Although the overall number of city and town residents will rise until 2050, the rural population, mainly influenced by the Democratic Republic of the Congo, is expected to peak in the 2040s and subsequently decline until 2050.

These new estimates will assist the United Nations in tracking progress towards its goals. Hertog noted that the aim is to achieve the 11th Sustainable Development Goal, which aspires to make urban areas more inclusive, safe, resilient, and sustainable by 2030. The outcomes will also be included in a report by the Intergovernmental Panel on Climate Change to help inform policies to mitigate climate change.

Factors driving urban population growth differ by region. In eastern and southern Asia, rural-to-urban migration is predominant. “People migrate not just for job opportunities and education, but also for social interactions,” according to Hertog. While international migration significantly influences Europe and North America, in sub-Saharan Africa, the rise is largely attributable to higher birth rates compared to death rates.

The increase in urbanization presents both challenges and opportunities for the environment. As urban populations expand city limits, improper public transport planning can lead to urban sprawl, increasing car dependency and carbon emissions. Conversely, thoughtful planning can yield more energy-efficient transit options than those offered in rural areas.

Urbanization also impacts health. For instance, residents in urban settings are typically more susceptible to air pollution and extreme heat, which correlate with issues like cardiovascular problems and a higher risk of Alzheimer’s disease, as stated by Andrea Mechelli from King’s College London. Moreover, the scarcity of green spaces in certain urban locales can lead to heightened anxiety and cases of depression, he emphasizes.

However, urbanization also offers health advantages. “Healthcare in urban settings tends to be more accessible and comprehensive compared to rural areas,” notes Mechelli. “Additionally, social connections are easier to establish in cities, where individuals can find like-minded people, unlike in rural regions where one might need to travel for hours to meet others with similar interests.”

This does not imply that urbanization should be halted or that city living is undesirable. Mechelli concluded, “This report underscores the urgency to enhance our urban environments, making them greener and more livable, which would yield numerous benefits.”