Protection of marine waters from the harmful consequences of nutrient enrichment is a challenge to resource managers because the sources and delivery routes of N and P are diverse. Combustion of fossil fuels produces gaseous nitrogen oxides, and animal production and fertilizer use produce volatile ammonia, two sources of atmospheric N that can be carried by winds and deposited on coastal waters and lakes hundreds of kilometers from their origin. Modern high-yield agriculture, golf courses, parks and urban gardeners presently use commercial fertilizers in large quantities -- substances that became cheap to produce in the mid 20th century – the era in which N and P concentrations began to increase in surface waters carrying agricultural and urban runoff to the sea. The world's human population is growing disproportionately in the coastal zone, creating an additional challenge of reducing nutrient inputs from municipal waste, septic systems, and fertilizer runoff from lawns and gardens. Projections indicate that the largest future increases in N and P delivery to the coastal ocean will occur in eastern and southern Asia where populations and economies are growing most rapidly.