Dead zone (ecology)
In March 2004 the newly established UN Environment Programme published its first Global Environment Outlook Year Book (GEO Year Book 2003). It said there were 146 dead zones in the world's oceans. In these zones marine life could not live due to low oxygen levels. Some of these zones were as small as a square kilometer (0.4 mi2), but the largest dead zone covered 70,000 square kilometers (27,000 mi2). A 2008 study counted 405 dead zones worldwide.