The official measurements are in, and the Gulf of Mexico "Dead Zone" is the second-largest ever recorded.
Hurricane Dolly, which churned through the Gulf last week, may have mixed in enough oxygen to thwart researchers' predictions that this year's Dead Zone would exceed the largest on record, in 2002. Had the survey been conducted earlier, before Dolly, the official estimate would have gone in the books as significantly larger.
But there's small consolation in a lifeless zone of water off the American coast that covers 7,988 square miles, slightly bigger than in 2007, and about the size of Massachusetts. It failed to reach the New Jersey-sized proportions predicted.
The biggest Dead Zone on record was in 2002, when 8,481 square miles of water became lifeless. Last year, researchers also predicted a record was possible, but the dead zone reached 7,903 square miles.
This year's Dead Zone is nearly four times the size government agents have set as a goal, and the average seasonal Dead Zone is more than three times the goal.
"The continuing presence of a large dead zone highlights the need to implement ways to reduce the amount of nutrients coming from the Mississippi River watershed which have contributed to the dead zone growth in recent years," said Rob Magnien, director of NOAA's Center for Sponsored Coastal Ocean Research. "Reducing nutrient pollution to protect coastal resources is one of the greatest ecosystem management challenges that we face nation-wide."
The Gulf Dead Zone was so large this year for several reasons.
One prime culprit: The record Midwest flooding that caused the Mississippi to swell. The discharge of pollutants and nutrients from the Mississippi River causes algae to bloom in the Gulf of Mexico. When the algae dies, the decaying absorbs so much oxygen from the water that large areas become inhospitable to fish. The resulting lifeless area is called a eutrophic or hypoxic zone, or more colloquially, a dead zone. The condition is cyclic, and reaches its maximum in late summer.
Researchers emphasized the exceptional flow of water from the Mississippi as a prime driver of their prediction, but the other major reason is the use of fertilizers on farms across the Midwest. In 50 years, since the advent of modern agricultural techniques and changes to federal farm policy, farmers have increasingly planted more corn per acre, which depletes the soil and requires heavier inputs of chemical fertilizer. Most nitrogen fertilizers are derived from natural gas, so they are essentially a fossil fuel for food.
The acreage of corn planted, and the use of fertilizer, has skyrocketed in the past couple of years as Congress set quotas on the use of ethanol, an alternative fuel that in the United States is made primarily from corn. As requirements to use more ethanol increased, so did corn acreage and fertilizer used.
Ethanol is seen as a valuable alternative to gasoline, but making it from corn has proved problematic because it takes so much land, drives up food prices by siphoning off corn for fuel use, leads to additional pollution and provides little more energy than it takes to produce. More promising plant sources of ethanol are being studied, including switchgrass, which can be used to make cellulosic ethanol. Biofuels are seen as a promising alternative to gasoline in part because the growing of crops absorbs some of the carbon emitted by burning the fuel, making them a more sustainable option than digging up long-buried hydrocarbons and putting them in the atmosphere.
The record flooding in the Midwest was attributed by many to global warming. At least, many scientists including those in federal agencies agree that this type of flooding is going to become more frequent and intense as the climate heats up.
So the dead zone in the Gulf of Mexico, which robs fishermen of valuable fishing grounds and harms or kills wildlife, can be seen as another consequence of global warming. In this case, a proposed solution to global warming is also fueling a serious environmental problem.
The world is getting familiar with the carbon cycle and how pumping carbon that's been buried for millions of years into the atmosphere causes some global problems, but the out-of-whack nitrogen cycle is just as problematic.
The World Resources Institute recently mapped the world's dead zones and found a whopping 415 eutrophic (nutrient-saturated) zones, including 169 that are known to be hypoxic (devoid of oxygen) and another 169 that probably are. The researchers believe the number is much higher, since only the United States and the European Union do an adequate job of counting and reporting problem coastal areas. China and other fast-growing Asian economies are likely polluting their coasts, but the problem hasn't been documented, the researchers say.
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