Using this graphic and referring to it is encouraged, and please use it in presentations, web pages, newspapers, blogs and reports.
For any form of publication, please include the link to this page and give the cartographer/designer credit (in this case Phillippe Rekacewicz, February 2006)
Global Environment Monitoring System (GEMS), Freshwater Quality Programme, United Nations Environment Programme (UNEP), 2001.
Uploaded on Thursday 16 Feb 2012
Biological oxygen demand - BOD: 1976-2008
Phillippe Rekacewicz, February 2006
The availability of oxygen is one of the most important indicators of the condition of a water body, because dissolved oxygen, or DO, (the amount of oxygen dissolved in water) is necessary for most aquatic organisms, including fish and invertebrates. Some species have very defined lower limits of DO that they can tolerate. Increases in DO can indicate improvements in water quality, such as has occurred in many parts of the world in the last 30 years.
Over the two decades, rivers in Europe and Australasia have shown a significant statistical reduction in biological oxygen demand concentrations, (an indicator of the organic pollution of freshwater), suggesting positive trends. There was no change in the assessed results for North America, although there was a tighter data distribution, indicating the data available for 1991-2000 is less variable than for previous periods.