Human populations in coastal zones have grown at unprecedented rates in recent decades. The United Nations (UN) estimates that 44% of the world's population (more people than inhabited the entire globe in 1950) live within 150 km (~93.2 miles) of the coast.1 In 2010, more than 123 million people, or 39% of the U.S. population, lived in coastal shoreline counties, yet these counties represent less than 10% of the continental U.S. land area. U.S. shorelines are expected to hold the most densely packed communities in the country by 2020, with 446 people per square mile (~2.6 km2) versus the national average of 105 people per square mile (excluding Alaska).2 In European Union (EU) countries that have a sea border, a majority of the population lives in statistical regions that are within 50 km from the sea; economic assets within 500 m of the sea in EU countries are estimated to have a collective value of between EUR 500 and 1,000 billion.3
Michelle E. Portman is with the Center for Urban and Regional Studies, Technion at the Israel Institute of Technology.
Tracey M. Dalton is in the Department of Marine Affairs at the University of Rhode Island in Kingston.
Jack Wiggin is at the Urban Harbors Institute at the University of Massachusetts Boston.