The Dead Zone Dilemma

Research Blogging / by Dave Munger /

Is saving our atmosphere killing our seas? Biofuels may stifle global warming, but scientists warn that agricultural runoff causes new problems.

Each year in April and May as farmers in the central US fertilize their crops, nearly 450 thousand metric tons of nitrates and phosphates pour down the Mississippi River. When these chemicals reach the Gulf of Mexico, they cause a feeding frenzy as photosynthetic algae absorb the nutrients. It’s a boom-and-bust cycle of epic proportions: The algae populations grow explosively, then die and decompose. This process depletes the water of oxygen on a vast scale, creating a suffocating “dead zone” the size of Massachusetts where few, if any, animals can survive.

The EPA has been working to reduce the size of the dead zone, with a goal of shrinking it to about 5,000 square kilometers—a quarter of its current size—by 2015. But a new study in Environmental Science & Technology shows that other efforts to preserve the environment may be exacerbating the dead zone. Kristopher Hite, a graduate student in biochemistry at Colorado State University, explains the implications of the study on his blog, Tom Paine’s Ghost.

The study examined the implications of a 2007 law that requires the US to annually produce 36 billion gallons of biofuels by 2022. Barring major biofuel production breakthroughs from sources like algae or microbes, most of this fuel will come from crops grown in the central US; the fertilizers and other agricultural waste they produce will flow straight down the Mississippi and feed the dead zone. Hite says the study, led by Christine Costello, found that meeting this goal will make it impossible for the EPA to reach its target reduction in the size of the dead zone. Even if fertilizer-intensive corn is replaced with more eco-friendly crops like switchgrass, the vast increase in agricultural production will cause the dead zone to grow unless preventive measures are taken.

So what can be done about it? The Society for Conservation Biology suggests that increasing the size of wetlands or other buffer zones around the source of the pollution—the farms themselves—could help.

Unfortunately, artificial wetlands have their own negative ecological side effects. As this post at Conservation Maven shows, some created wetlands are dominated by invasive species. Apparently, the heavy equipment used to build the sites also compacts the soil in a way that makes it more difficult for native species to flourish.

But not all human-made wetlands are bad. Conservation Maven also points to a Swedish study which found that less-diverse wetlands dominated by tall plants are actually more efficient at removing nitrogen from runoff than many other sites. So creating wetlands can be a very effective means of removing pollutants from water, even if local biodiversity suffers. The current pace of biofuel development, however, exceeds the capacity of available wetlands.

Hite remains an optimist, pointing to new technology that uses fungi to convert the cellulose in wood chips, corn stalks, and other agricultural “waste” into biofuels. If this can be done efficiently, we could eventually harvest several times more energy from the same amount of cropland. Even while acknowledging that we may still face problems like the Gulf’s dead zone, Hite believes that ultimately technology can help us prevent greater ecological disasters like global warming.

But should Hite even be making this case? How do we decide whether it’s ecologically sensible to produce biofuels or build wetlands? Some have argued that the advocacy of scientists like Hite and websites like Conservation Maven is misplaced. Shouldn’t scientists just be interested in giving us the facts, staying removed from policy decisions and letting the general public and politicians decide how to act? Doesn’t becoming an advocate introduce bias into the scientific process, potentially tarnishing results?

James Hrynyshyn is a freelance journalist and unapologetic environmental advocate who says that many of the best scientists, from Albert Einstein, to Carl Sagan, to NASA’s James Hansen, have also been important policy advocates. On his blog, The Island of Doubt, Hrynyshyn cites a May paper in Conservation Biology by Michael Nelson and John Vucetich, who argue that scientists’ advocacy positions can easily be separated from scientific truths. For instance, late in his life the great chemist Linus Pauling damaged his reputation by peddling vitamin C as a cure-all, but that didn’t take away from his earlier scientific contributions, for which he won two Nobel prizes.

More importantly, Hrynyshyn says, it’s unfair and unwise to restrict individuals—who are interested citizens as well as working scientists—from participating in the political process, especially when those individuals have knowledge and expertise that applies directly to important problems. Conservation biologists can both alert us to potential ecological disasters and offer insight into how to solve them. Why not tap their expertise to help form policy decisions?

There’s much more discussion of ecology—and ecologists’ role in creating environmental policy—at

Originally published September 30, 2009

Tags climate consensus ecology research risk

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