Cities are supposed to be one of the defining characteristics of civilisation, but I think Madison Grant said that cities would destroy the Nordic (northern European light-skinned/eyed) people.
https://www.amazon.com/Passing-Great-Race-Madison-Grant/dp/1389865827/ref=sr_1_2?s=books&ie=UTF8&qid=1524459091&sr=1-2&keywords=the+passing+of+the+great+race
Writing in the early part of the 20th century, he did not anticipate the spew of pollution which we now swim in:
http://www.collapse.news/2018-04-21-city-life-is-killing-humanity-95-of-humans-living-today-are-breathing-polluted-air-mostly-from-cities.html
“Even if you don’t have any unhealthy habits, something that you do every day could be killing you: breathing. A new report from the Health Effects Institute shows that more than 95 percent of the people on our planet are breathing in air that is unsafe. Unfortunately, it’s those who live in the poorest communities that are being hit the hardest. While cities are packed with people and can expose millions of individuals at once to unsafe air, the risk of indoor air pollution in rural areas should not be underestimated. Around 2.6 billion people were exposed to air pollution in 2016 due to the burning of solid fuel like biomass or coal in their homes to stay warm or cook.
Indoor air pollution also impacts the quality of air in the areas surrounding it. This number has dropped in recent years, but it’s still shockingly high. Meanwhile, around a third of people around the world have to contend with the misfortune of breathing in unsafe air inside as well as outdoors. Another cause of air pollution is the emissions from transportation, with diesel fuel being a big cause of air pollution in well-off countries like the U.K. In poorer nations, many people drive cars that are older and in bad condition, and these vehicles are linked to fine particulate matter that causes millions of deaths annually.”
In 2017 over six million peole died from causes linked to air pollution such as lung cancer, chronic lung disease, heart attack and stroke, with over half of these deaths being in India and China. Thus, city life is killing us, but it is hard to see any alternative to what we now have, since few are willing to give up comforts, and in any case, the elites want this sort of world, so we had better like it, or shut up. A small number will move to rural living, to continue the human line.