Environmental Effects of Growing Energy Crops

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News this week that the dead zone in the Gulf of Mexico, caused by agricultural run-off from the mid-west, is again this year going to be quite large.

There is some disagreement about exactly how large.  A article from Minnesota Public Radio leads off with: "A scientist with the National Oceanic and Atmospheric Administration, NOAA, says this summer's dead zone could be as large as 8500 square miles. That's 77 percent larger than the average size of the dead zone over the last two decades."

The article continues:

The issue of nitrogen is especially important this year because it's the main fertilizer used on the nation's corn crop.

U.S. farmers this spring planted one of their largest corn crops ever, up almost 20 percent from a year ago. Much of the increase will go to meet the demands of the ethanol industry.

Runoff from farm fields carries nitrogen into streams and rivers and eventually the Gulf of Mexico. NOAA's David Whitall says the corn-biofuels-dead zone link is one area researchers will examine as they search for answers.

...One federal study says if ethanol production continues to expand, nitrogen loads to the Gulf could increase another 30 percent.

At CNN, on the other hand, the size of the dead zone is portrayed somewhat differently:

The oxygen-poor "dead zone" off the Louisiana and Texas coasts isn't quite as big as predicted this year, but it is still the third-largest ever mapped, a scientist said Saturday.

...The 7,900-square-mile area with almost no oxygen, a condition called hypoxia, is about the size of Connecticut and Delaware together. The Louisiana-Texas dead zone is the world's second-largest hypoxic area, she said.

This year's is about 7.5 percent smaller than [had been] predicted, judging by nitrogen content in the Mississippi River watershed.

[Previous predictions were] about 8,540 square miles, which would have made it the largest measured in at least 22 years. More storms than normal may have reduced hypoxia by keeping the waters roiled.

No mention at CNN of any role any role in the dead zone of biofuels.  The difference between the numbers cited by the two sources is less than 5%, which probably isn't a big deal, especially give then fact that neither article cites error bars.  But there is a difference in focus.  On the one hand, the dead zone is bigger than ever, on the other, not so bad.  Corn acres are certainly up in the U.S., and the effects of the consequent increase in irrigation and fertilizer use is something to keep an eye on.

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