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Nutrient over-enrichment of freshwater and coastal ecosystems, or eutrophication, is a rapidly growing environmental crisis. Worldwide, the number of coastal areas impacted by eutrophication stands at over 500. In coastal areas, occurrences of dead zones, which are caused by eutrophic conditions, have increased from 10 documented cases in 1960 to 405 documented cases in 2008. In addition, many of the world’s freshwater lakes, streams, and reservoirs suffer from eutrophication; in the United States, eutrophication is thought to be the primary cause of freshwater impairment. Many of our largest freshwater lakes are entrophic, including Lake Erie (United States), Lake Victoria (Tanzania/Uganda/Kenya), and Tai Lake (China).

The increase in eutrophication is the result of human activities. Major sources of nutrients to freshwater and coastal ecosystems include wastewater, agriculture, and atmospheric deposition of nitrogen from burning fossil fuels. The drivers of eutrophication are expected to increase for the foreseeable future. Specifically:

• World population will continue to grow, reaching an estimated 9.2 billion by 2050, which will increase pressures on the productive capacity of agriculture and industry.
• Intensive agriculture and land use conversion—for crops, livestock, and aquaculture—will increase, especially in the developing world. In addition to population growth, intensifi cation is driven by changing dietary patterns. For example, over the period from 2002 to 2030, global meat consumption is expected to increase by 54 percent.
• Energy consumption is expected to grow 50 percent from 2005 to 2030. Fossil fuels, which release nitrogen oxides (NOx) into the environment when burned, will continue to be the dominant fuel source in this century.

As a result of these increasing global trends in population growth, energy use, and agricultural production, we expect that coastal and freshwater systems impacted by eutrophication and hypoxia will continue to increase, especially in the developing world.