Saturday, February 09, 2008

Science Focuses on Cities

The latest issue of Science is a special issue on the topic of cities. There are a number of interesting articles, like Ruth Mace's "Reproducing in Cities" and Christopher Dye's "Health and Urban Living". Here are a few samples:

"Reproducing in Cities" by Ruth Mace

ABSTRACT: Reproducing in cities has always been costly, leading to lower fertility (that is, lower birth rates) in urban than in rural areas. Historically, although cities provided job opportunities, initially residents incurred the penalty of higher infant mortality, but as mortality rates fell at the end of the 19th century, European birth rates began to plummet. Fertility decline in Africa only started recently and has been dramatic in some cities. Here it is argued that both historical and evolutionary demographers are interpreting fertility declines across the globe in terms of the relative costs of child rearing, which increase to allow children to outcompete their peers. Now largely free from the fear of early death, postindustrial societies may create an environment that generates runaway parental investment, which will continue to drive fertility ever lower.

And from Dye's "Health and Urban Living":

For the citizens of 18th century London and Paris, it was the worst of times. As far as public health was concerned, the best of times would be for future generations. By modern health standards, London in the 1700s was a slum: Between 10% and 30% of infants died before their first birthdays, and although the death rate of young children was lower in richer parts of the city, there was little variation in life expectancy across social classes. Edwin Chadwick's "sanitation revolution" gained momentum in the early 1800s and was given greater impetus by the Public Health Act of 1848, but even in 1858, the River Thames brought "the sewage of three millions of seethe and one vast open cloaca.". Conditions were no better in 19th century Paris: Relatively high food prices and poor sanitation left Parisian men more stunted than men elsewhere in France. In Europe today, about 70% of people live in urban areas. In the Europe of 1800, only 10 to 15% of people did so, partly because of the atrocious living conditions. Cholera, dysentery, measles, plague, smallpox, tuberculosis, typhus, and other infections, exacerbated by undernourishment, imposed an "urban penalty" such that deaths, mostly of children, exceeded births. London, Paris, and other European cities could only grow by immigration from the countryside.

The 1848 act focused on sanitation—piping clean water to homes and safely disposing of human waste—but led on to a wider range of environmental improvements that had benefits for health, including ventilation of dwellings and streets, the preservation of green spaces, and the upgrading of road surfaces (6). By the start of the 20th century, urban health was typically improving faster than rural health in the industrialized world, and towns and cities grew faster than their hinterlands. As cities expanded, they started to provide a variety of indirect benefits to health: large markets with a steady and diverse food supply, economies of scale with low transportation costs, organized public services, and a critical mass of educated people that was needed to establish centers of enterprise, learning, and innovation.

Today, more than half the world's population—about 3.3 billion people—lives in urban areas, including roughly 50,000 settlements of at least 50,000 people. By 2015, and for the foreseeable future beyond, population growth will be mainly urban, mainly in the 500 or so cities that have 1 million to 10 million inhabitants, and mainly in poorer countries. Although three-quarters of the people who earn less than a dollar a day still live in rural areas, the proportion and number of poor people living in urban areas are rising. About one in three urban inhabitants—roughly one billion people—now live in slums, but the proportions are much higher than this average in sub-Saharan Africa and South Asia.

....Many of the prescriptions for better urban health are in fact self-evident and are often inexpensive: healthy housing, primary health care, communicable disease control through sanitation and vaccination, safe roads, and targeted assistance to women. They are also not specific to urban areas. The tough problem is that technical solutions need a framework in which they can be executed. Hence, the call for "healthy governance," regulated land ownership, probity in financial investment, social cohesion, the empowerment of civil society, and foresight in planning the physical environment. The right structure is hard to create because there are no recipes for social cohesion and good governance. Yet there is an imperative to succeed: If cities are the "defining artifacts of civilisation", a nation may now be judged by the health of its urban majority.