Short answers, pulled from the story.
Urbanization is the process by which human settlements form and grow as more people live, recreate and work in cities and towns. It describes the population shift from rural to urban areas, the falling proportion of people in rural areas, and how societies and culture adapt. It refers to the proportion of a national population living in areas classified as urban, not just the absolute number of city dwellers.
According to the UN, 2007 was the turning point when more than 50% of the world population was living in cities for the first time in human history. At the turn of the 20th century, just 15% of the world's population lived in cities.
By 2050, forecasts put about 64% of the developing world and 86% of the developed world as urbanized. The predicted urban population growth is roughly 3 billion urbanites by 2050, much of it in Africa and Asia. The UN projects about 1.1 billion new urbanites from 2017 to 2030.
People move to cities because money, services, wealth and opportunities are centralized there, offering access to the labour market, education, housing and safety. Rural flight also drives urbanization, since farm life is exposed to drought, flood and pestilence. Conflict over land rights from globalization has forced less powerful groups such as farmers into cities.
Urban areas more than doubled from 33 million hectares in 1992 to 71 million hectares in 2015, consuming 24 million hectares of fertile cropland. Urbanization creates urban heat islands, urban runoff that pollutes streams and rivers, and eutrophication in water bodies. The ocean absorbs a quarter of human CO2, which makes it more acidic.
Urbanization shifts diets from plant-based rural eating toward processed foods higher in meat, sugar, refined grains and fats, raising obesity, as seen in Thailand. Nearly 23.5 million people in the United States lack a supermarket within one mile, creating food deserts. Rapid urbanization also raises mortality from non-communicable diseases like cancer and heart disease, and increases asthma risk.
The global urbanization average was 56.2% in 2020. As of 2022, rates exceed 80% in countries including the United States, Canada, Japan, Australia and South Korea. South America is the most urbanized continent, with more than 80% of its population in urban areas. China reached 54% urbanization compared with India's 36%.