Coastal cities: living on the edge

Environmental Health Perspectives, Nov, 2002 by John Tibbetts

In one of the greatest human migrations of modern times, people are flocking to coast, lines around the world. People in developing countries have relocated from the countryside to towns and cities of every size during the past 50 years. But the most dramatic population growth has occurred in giant coastal cities, particularly those in Asia and Africa. Many experts argue that cities will have to cope with almost all of the population growth to come in the next two decades, and much of this increase will occur in coastal urban centers.

Cities concentrate people and businesses--and their wastes. Yet most large cities around the world lack adequate provisions for treating their domestic and industrial wastes, which pour into coastal waters. At the same time, booming cities are sprawling across coastal environments, destroying important resources. These problems and the scale of population growth are most alarming in the tropics. Some coastal cities in the tropics are doubling their population in just a decade, so the pace of ecosystem change is much greater there.

Cities Take Center Stage

In 1950, New York City was the planet's only "megacity," defined as a city with more than 10 million people. Now there are 17 megacities around the globe, and 14 are located in coastal areas. Eleven of today's megacities are located in Asia, and the fastest-growing ones are located in the tropics. The United Nations (UN) Population Division anticipates four new megacities by 2015, including Tianjin, Istanbul, Cairo, and Lagos. All but Cairo are located on coastlines.

But megacities are just one part of the population boom in coastal areas. Two-fifths of the world's major cities of 1-10 million people are also located near coastlines. In 2001, almost 3 billion people worldwide lived in an urban center--generally defined as a town or city of more than 1,000-2,000 people--and by 2030 that number will likely increase to 5 billion. This population growth will be especially heavy in coastal urban areas of less-developed countries. By contrast, the percentage of people living in cities in North America, South America, Europe, and Japan is expected to remain stable at 75-85%.

Coastal populations on every continent have exploded as global trade has flowed into coastal nations through international ports, creating jobs and economic growth. The world economy grew more than fivefold between 1950 and 1990. The internationalization of finance, production, and services, plus advances in information technology and cheap labor, reduced physical boundaries around the world. Cities such as Sao Paulo, Buenos Aires, and Jakarta prospered after deregulation of financial markets, and their urban cores flourished with Western-style, high-income commercial and residential gentrification.

Rapid development and population growth are causing similar problems along shorelines around the world, according to a report in the January-March 2000 issue of Coastal Management by Stephen Olsen, director of the Coastal Resources Center at the University of Rhode Island, and Patrick Christie, a research assistant professor at the University of Washingtons School of Marine Affairs. Important habitats such as wetlands, coral reefs, sea grasses, and estuaries are being degraded or destroyed. Changes in the volume and quality of freshwater inflows to estuaries have affected water quality. As a result, estuary-dependent fish and shellfish populations and their associated fisheries are declining.

Moreover, fishermen are losing access to their fishing grounds. Resorts, hotels, and condominiums are usually built in attractive bays, inlets, and creeks that fishermen have traditionally used as docking facilities and fishing grounds. In many coastal areas, tourism drives up the cost of shorefront land, making it difficult for fishermen to live and work there. At some point, fishermen lack a place to sustain the infrastructure they need to ply their trade.

Coastal Growth in the United States

Many Americans are moving from high-density, cold-weather urban centers in the Northeast and Midwest to warm-weather, lower-density, suburban resort communities throughout the Sun Belt, including shorelines from Virginia to Texas, and also to the Pacific Coast, particularly Southern California. Of the 20 fastest-growing U.S. counties, 17 are coastal. Coastal counties cover less than 20% of the land area of the United States, but today they account for more than half of the nation's population.

According to the December 2001 report State oft he Coast, published by the National Oceanic and Atmospheric Administration (NOAA), the coastal population will grow to 165 million by 2015, a 50% increase over 1960. But the coastal portion of the U.S. population has remained stable since 1960 and will continue that way. The coastal portion has averaged about 54% of the national population total since 1960, and it's expected to remain the same to 2015.

Along U.S. shores, financial and entertainment centers such as New York and Los Angeles have continued as dominant forces in the world economy. At the same time, these metropolitan areas have seen striking changes in land use patterns since the 1950s. High-density development has boomed near harbors and on barrier islands, where land values are extremely high. But low-density development has also gobbled up laud in every coastal watershed, because Americans want to live in lower-density settings. "You see this massive outward flow around the United States," says Kenneth M. Johnson, a demographer and sociologist at Loyola University Chicago. As a result, many metropolitan areas have grown outward physically far more rapidly than their populations have risen.