The history of the 19th and 20th centuries could fairly be characterized as the history of urbanization. Today, every culture is rife with stories of the trek from the countryside to the city in search of work, education, sophistication, power and money. To stay behind was to be condemned to a life of parochialism and poverty. Will the history of the 21st century be more of the same?
It's starting out that way. Every year countless millions continue to stream into the metastasizing boundaries of Shanghai, Bangkok, Jakarta, Dhaka, Calcutta, Lahore, Cairo, Lagos, Nairobi, Johannesburg, Rio De Janeiro, Caracas, and Mexico City. Countless millions more are crowding into the ever sprawling urbanized areas surrounding so-called world-class cities such as Tokyo, Singapore, London, Paris, Rome, Toronto, New York, Seattle, Chicago, Los Angeles, Houston and myriad other vibrant modern cities across the globe. The attraction of the city for the young has never been so strong. This migration has become like a howling wind that will blow back anyone who tries to walk in the opposite direction.
Yet the forces which have made all of this migration possible seem like they are coming to an end. The fabulous advances in food production of the last century are slowing. We are having a harder time keeping up with population growth. This is partly the result of a self-reinforcing loop in which more urban growth means more land for housing and infrastructure and the consequent destruction of fertile farmland needed to feed this growing population. The result of this and other factors has been that per capita grain yields which peaked in 1984 have actually declined. Yes, there is overall more food available; but the key figure--as anyone who has gone hungry can tell you--is food per person. Naturally, people eat things other than cereal grains. But for most of the world, cereal grains are the central source of food calories; some 80 percent of all calories eaten are in the form of grain products and the products of livestock fed on grains.
We face a litany of other problems as well: the overuse of underground and surface waters, the collapse of fisheries, climate change, deforestation, loss of biodiversity, toxic pollution, and the depletion of strategic minerals. In addition, the growth in world oil production appears to be stalling out. Yet, against this backdrop, waves of humanity keep washing into the world's cities.
It is like the momentum of the tides which take water further up onto the beach even as the gravitational force which brought that water there is waning. People continue to come into the cities despite all the challenges of doing so because the whole system--even as it frays at the edges--practically forces them to.
Those who are concerned about sustainability talk about making cities more sustainable. But that is an oxymoron. Cities have never been sustainable. They have always needed more from the land than the land under them could give. But the issue is more nuanced than that. On the one hand, living more densely in an energy-constrained world makes sense. It reduces travel for all purposes, economic and social. And, in the past people did live in walkable villages and towns. Some still do. But today, at least in North America, only those living in large cities can really do without a car.
On the other hand, the explosive expansion of urban areas is primarily driven by economic growth and rising population. These two trends will be called into question in the energy-constrained world that is emerging in the 21st century. Without cheap energy it will be difficult to keep food production and economic growth on its current upward path. And, even if the two continue to rise, they may not do so at a rate that satisfies the world's hunger for both food and energy.
But try encouraging people to stay put in their rural landscapes when the hope of a better life is all in the city. Part of the reason is that the rural landscape is being systematically decimated by city residents through soil degradation (due to industrial farming); voracious mineral extraction and its often toxic side effects; and the felling of forests for fiber and to clear land for more agriculture. Add to this the persistent underfunding of public infrastructure and services in rural areas.
The ideal among serious thinkers about sustainability is a more decentralized living arrangement than we currently have--and one that is much lighter on the land and the entire ecosphere, of course. But the continuing crush of people moving toward the world's cities may not stop anytime soon even in the face of declining energy supplies. In part that's because the alternative, the countryside, has been so damaged in many places that it offers no alternative at all for the teeming millions in the cities.
What this means is that we will be obliged to figure out how to make our cities, even our megacities, somehow work even as the challenges of climate change and resource depletion begin to hit us full force. At this date that seems an impossible task. Perhaps in the long run we will be able to make living in the countryside and its villages and towns attractive to most people again. For now we will have to do what we can to respond to the growing number whom the lure of the city is bringing within its borders every day.