<a href="//commons.wikimedia.org/wiki/Red" class="mw-redirect" title="Red">Red</a> <a href="//commons.wikimedia.org/wiki/Circles" class="mw-redirect" title="Circles">circles</a> on this map show the location and size of many of <a href="//commons.wikimedia.org/wiki/Earth" title="Earth">our planet’s</a> <a href="https://en.wikipedia.org/wiki/Dead_zone_(ecology)" class="extiw" title="en:Dead zone (ecology)">dead zones</a>. <a href="//commons.wikimedia.org/wiki/Black" class="mw-redirect" title="Black">Black</a> dots show where dead zones have been observed, but their size is unknown. It’s no coincidence that dead zones occur downriver of places where <a href="//commons.wikimedia.org/wiki/Homo_sapiens" title="Homo sapiens">human</a> population <a href="//commons.wikimedia.org/wiki/Category:Density" title="Category:Density">density</a> is high (darkest <a href="//commons.wikimedia.org/wiki/Brown" class="mw-redirect" title="Brown">brown</a>). Darker <a href="//commons.wikimedia.org/wiki/Blue" title="Blue">blues</a> in this image show higher concentrations of particulate organic matter, an indication of the overly fertile waters that can culminate in dead zones.
Robert Simmon &amp; Jesse Allen
2010-07-17
<a rel="nofollow" class="external text" href="http://earthobservatory.nasa.gov/IOTD/view.php?id=44677">NASA Earth Observatory</a>