The effects of global change and regional human activities are especially pronounced in the coastal zone, a highly productive and dynamic environment that includes the continental shelves, estuaries, bays, lagoons, and the Great Lakes. Although estuaries and continental shelf waters comprise less than 10% of the Earth's surface, they account for about 25% of global biological production, store 90% of the global sedimentary accumulation of organic carbon, and support over 75% of U.S. fisheries. Nearly 50% of the U.S. population inhabits coastal counties that make up 10% of the nation's land area and account for at least 30% of the nation's gross national product.