Dead Zones

Abstract

This book explores the many rivers, lakes, and oceans that are losing oxygen. Aquatic habitats with little dissolved oxygen are called dead zones because nothing can live there except some microbes. The number and size of dead zones are increasing worldwide. The book shows that oxygen loss causes fish kills, devastates bottom-dwelling biota, reduces biological diversity, and rearranges aquatic food webs. In the 19th century in rich countries and in poor regions today, dead zones are accompanied by waterborne diseases that kill thousands of people. The open oceans are losing oxygen because of climate change, whereas dead zones in coastal waters and seas are caused by excessive nutrients, which promote excessive growth of algae and eventually oxygen depletion. Work by Gene Turner and Nancy Rabalais demonstrated that nutrients in the Gulf of Mexico come from fertilizers used in the US Midwest, home to the most productive cropland in the world. Agriculture is also the biggest source of nutrients fuelling dead zones in the Baltic Sea and other coastal waters. Today, fertilizers contaminate drinking water and kick-start harmful algal blooms in local lakes and reservoirs. Nutrient pollution in some regions has declined because of buffer zones, cover crops, and precision agriculture, but more needs to be done. The book concludes by arguing that each of us can do our part by changing our diet; eating less, especially eating less red meat, would improve our health and the health of the environment. A better diet could reduce the amount of greenhouse gas emitted by agriculture and shrink dead zones worldwide.