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The Dead Zone

Below the Mississippi River, the Gulf of Mexico is choking to death, and midwestern farmers are the prime suspects.



If, for two or three months each summer, dead animals were strewn over 18,000 square kilometers of land in Missouri or Iowa, people would rightly be upset, and efforts would be immediately undertaken to correct the situation. --Douglas Harper Jr. and Nancy Rabalais

Every summer, a thousand miles from Chicago in a murky dark place where you and I have never been, the air starts to go away. Every creature leaves--if it can. Those that can't get away strain for the little oxygen that remains. Snails wander around with their siphons sticking straight up. Hermit crabs come out and lie on top of their borrowed shells. Worms emerge from the mud. Starfish lie on their burrows.

In some of the worst places they eventually suffocate. Occasionally their bodies don't even decompose.

Welcome to the hypoxic zone, located where the Mississippi River meets the Gulf of Mexico. ("Hypoxic" means the water contains less than two parts of oxygen per million parts of water--the point at which gulf trawlers don't catch any fish or shrimp.) Sixty years ago the hypoxic zone didn't exist. Six years ago it was only half as big as it is now. For the last five summers it has extended along the shore roughly from New Orleans to Houston--an area seven times the size of Cook County.

Nasty as it is, the hypoxic zone includes only about 1 percent of the gulf. And it's not permanent; every fall it breaks up as storms mix oxygen into the water. (Fish and shrimp and snails then return for another nine or ten months, though the ecosystem can't fully restore itself in that time.) Nor is it the worst such area in the world; two bigger and more severely depleted zones in the Black Sea and the Baltic Sea have killed fish and ruined fisheries. That hasn't happened in the gulf--yet.

It's no coincidence that this zone appears where the Mississippi River flows into the sea, carrying water from the Appalachians, the Rockies, and pretty much everywhere in between. In all likelihood, the hypoxic zone is a gift from unwitting midwesterners.

Wendell Shauman farms a thousand acres of coal black western Illinois soil so flat it would put a billiard table to shame. I spoke with him on a cloudy, threatening spring day when he was in a hurry. "I've got half a wagon of fertilizer stuck out in the field," he said, "and I want to get it in before it rains."

Fertilizer was just what I wanted to talk about. According to one theory, snails and starfish in the gulf die every summer because Shauman and people like him put too much anhydrous ammonia on their cornfields. Call it the Bad Fertilizer Theory. It's popular and plausible, but not quite proved yet.

To produce a good crop, corn needs more nitrogen than even fertile soil can usually provide. It can't use the abundant nitrogen in the air, so most farmers in this country give it a fertilizer that's produced by combining nitrogen from the air with hydrogen--a process first tried in Germany in 1910. "Anhydrous" is the most popular form.

Shauman holds a PhD in corn breeding and serves on the boards of the Illinois Farm Bureau and the Illinois Soybean Association. But, as he says, you don't need a lot of expertise to look up the rule of thumb for fertilizing in the latest Illinois Agronomy Handbook: it takes about a pound of nitrogen to grow 1.2 bushels of corn. (Farmers still measure corn this way, even though bushel baskets no longer play a role in the harvest.) So how much nitrogen should Shauman put on his fields?

Just as a big dog eats more food than a small one, a tall, thick stand of corn consumes more nitrogen than a stunted, thin one. In a perfect world, Shauman would put only as much nitrogen on the ground as the corn would need, and he'd apply it right before the corn needed it. Then the corn would quickly take it up, and little or none would escape downstream. But in this world, he has to apply fertilizer early--perhaps in the fall before planting, or in the spring before planting, or at the latest when the corn is still short enough to accommodate a tractor--and he can't predict what the weather will do to his crop after that. In other words, he has to put the food down before he knows what size dog he's feeding.

As a demonstration of how hard it is to know how much fertilizer to use, Shauman told me in early April, "There are two schools of thought about El Ni–o. In other years it has led to a midwestern drought"--in which case the crop will be small and he should apply less nitrogen. "The other group says the timing is off and our summer will be pretty normal"--in which case he should apply more nitrogen. "I've got to make a decision this week."

If Shauman fertilizes for good weather but it doesn't rain from June to September, then he'll lose money--and when the fall rains finally come, his fields will lose a lot of nitrogen in runoff. (Unlike other kinds of fertilizer, nitrogen dissolves in water and doesn't necessarily bind to soil particles, so even a conservation-minded farmer who guards against soil erosion may see his nitrogen investment head downstream.) If Shauman fertilizes for drought but we have regular rains, he'll harvest a lot less corn than he could have--maybe not even enough to pay his bills.

Having made this call year after year, Shauman has no taste for other forms of gambling. "We had a national meeting in Reno," he says with a quick grin, "and I never spent a nickel."

Of course nitrogen is a nutrient, not a poison. It builds protein in plants and animals. We wouldn't want to reduce it to zero in rivers or the gulf even if we could. "Louisiana's fisheries, and to a large extent those of the northern Gulf of Mexico, depend on the Mississippi River for their existence," state fisheries experts told an EPA hypoxia management conference in New Orleans in December 1995. The river delivers nutrients they need.

But nitrogen can be a problem for the same reason that phosphate detergents became a problem in some lakes and rivers in the early 1970s--it becomes too much of a good thing. More fertilizer (phosphate then, nitrogen now) enables more algae to grow. More algae become food for other sea creatures, including eventually the fish and shrimp that fuel a $2.8 billion industry on the gulf.

But more algae also mean more dead algae that sink to the bottom, where they "decay"--i.e, become food for an army of bacteria. Those bacteria have to breathe, and they use up much of the oxygen that's dissolved in the water--oxygen that everything else down there needs to survive. Plenty remains near the surface. But as the weather warms and the winds calm, the near-shore gulf comes to resemble a layer cake, with warmer oxygen-rich freshwater from the Mississippi lying on top of saltier, cooler gulf water. The dissolved oxygen on top doesn't get mixed with the water below. Fish swim away, shrimp migrate to a more favorable habitat, and the less-mobile bottom dwellers start gasping.

Has it always been thus? Occasionally, yes. Regularly, no.

Louisiana marine scientists Nancy Rabalais and Eugene Turner are the premier experts on the hypoxic zone. But they've been systematically surveying it only since 1985. Their 13 years' worth of data aren't enough to show whether today's zone is a human-created pestilence or just part of a long-term natural cycle. Earlier records are few, scattered, or from much deeper waters farther out in the gulf.

But Rabalais and Turner and geologist B.K. Sen Gupta have found a way to track hypoxia through the ages. They picked two tiny protozoans with perforated shells to serve as indicator species. One, Ammonia parkinsoniana ("A"), can tolerate hypoxia; the other, Elphidium excavatum ("E"), can't. They took cores of sediment from the bottom of the gulf dating back to the early 1700s, counted the dead As and Es in each layer, and compared numbers of the two species in each layer by calculating what they call an "A-E index." If hypoxia were a natural phenomenon--as skeptics and farmers sometimes claim--you'd expect the relative numbers of the two species to stay roughly the same over the years, or to cycle back and forth without any clear direction. Instead, the three scientists found a trend.

Sediment cores from the 1700s show that a group of 100 As and Es typically would have been made up of about 60 As and 40 Es. During the 1800s that ratio gradually changed to 70 As to 30 Es. Around 1920 it shot up to 80 to 20, and in recent years it has risen to 90 to 10, sometimes even 100 to 0. This unprecedented domination by Ammonia parkinsoniana is powerful evidence that current levels of hypoxia are something new under the sun.

"Seasonal hypoxia in the Mississippi bight has increased in intensity or duration, or both, for about 200 years," Rabalais and Turner concluded in the March 1996 issue of Geology. "The A-E index shows that the oxygen depletion...has become severe in the 20th century, especially since the 1950s."

If the Bad Fertilizer Theory is true, then midwestern farmers can shrink or eliminate the hypoxic zone by being better farmers and keeping excess fertilizer out of rivers. One way to do that is to fertilize less; another is to keep any unavoidable excess away from running water.

Some techniques would actually save farmers money:

9 They could make better estimates of their corn yield by scrutinizing the most reliable forecasts and not being overoptimistic.

9 They could count any manure they apply as part of the total nitrogen a field gets--a seemingly obvious procedure that's not always followed.

9 They could apply fertilizer only in the spring, rather than in the spring and fall, and apply any additional nitrogen next to the small corn plants in late spring or early summer. That way farmers would be closer to the summer weather and better able to predict it.

Other techniques would be more costly. "Precision agriculture"--using computers to keep track of yields and soil types and other factors on every square foot of every field--enables farmers to predict corn yields more accurately and apply more precise amounts of fertilizer. Buffer strips of grass can be allowed to grow along creeks and rivers to retain some nitrogen runoff and convert it into less available forms. Wetlands--including man-made ones--can do that job even better.

Are farmers bad stewards for not doing these things already? Maybe so, maybe not. None of these practices is as simple as it sounds to urbanites. Putting nitrogen on in the spring seems like an easy commonsense idea--unless you know that spring is the rush hour of the year. Farmers already have to plow and plant in the few dry, frost-free days available each spring. If they have to do all their fertilizing then too, they may run out of time or help. If they invest big money in precision-agriculture computers and equipment, they then have to analyze thousands of lines of data to figure out how to best manage each square foot. Building wetlands to hold nitrogen isn't cheap either, and according to an April 17 article in Science, constructed wetlands have yet to prove themselves to be as good as natural ones at processing nutrients.

What makes farmers like Shauman a bit testy is that none of these ideas is impossible to carry out. But each one makes their job a little bit harder to do. Added together they start to feel like a heavy burden imposed by people whose knowledge of farming is limited to 65-mph surveys.

The battle lines in this dispute were drawn a long time ago. Many farmers already feel underappreciated in a society that rewards talking heads more than productive hands. Some take this resentment a step further. The American Farm Bureau Federation's "Public Policy Digest" asks, "Will Hypoxia Become Farmer's Spotted Owl?"--because many farmers believe that the fuss about hypoxia is just one more environmental scare that could damage a regional industry. Last fall Nebraska Farm Bureau Federation president Bryce Neidig wrote in the bureau's newsletter, "I have never been a believer in any sort of conspiracy theory, but I am just about to believe that the environmental extremists are at least attempting to be part of a conspiracy against production agriculture."

A sense of persecution isn't surprising given that farmers have gone from a minority to a tiny minority within living memory. Those who would regulate them often don't seem to understand farmwork or take it for granted. And the farm press has passed along plenty of half-truths and misunderstandings--such as that the current level of hypoxia is natural and that traditional soil- conservation measures retain nitrogen.

On the other side of the battle line, environmentalists tend to like the Bad Fertilizer Theory because of their complicated love-hate relationship with agriculture. They're not comfortable with the way industrial-scale farms, which rely on capital and chemicals, have displaced small "family" farms, which depend on labor and animals. Enviros such as Paul Ehrlich and Lester Brown have built careers on predicting the imminent failure of modern farming, decade after decade. Others, such as Barry Commoner, have documented specific misdeeds. In his 1972 book The Closing Circle, he described the pollution of downstate Decatur's water supply by nitrates, one of the most common forms of nitrogen, from farm fertilizer. Environmentalists these days are also looking at a bigger picture than dead worms in the gulf. Most scientists agree that estuaries worldwide are getting more nutrients than they can use, and some have recently warned that humans are now manufacturing as much biologically usable nitrogen as natural processes do--creating a gigantic nitrogen glut that may upset the nitrogen cycle more than our production of greenhouse gases has upset the carbon cycle. The nitrogen glut appears to favor a few weedy plants, threatening biodiversity as well. If nitrogen is a global as well as a regional problem, then the Farm Bureau's worst fears may yet prove accurate--that environmentalists ultimately want to "either significantly reduce fertilizer application rates...and/or the cultivation of land in the Mississippi and related watersheds."

Environmentalists fuel their doubts about farmers' stewardship with their own set of colorful exaggerations--they refer to the hypoxic zone as the "Dead Zone," assert that "the only things oceanographers have been able to find alive in this zone are other oceanographers," and claim that fertilizer production has increased "exponentially."

So the Bad Fertilizer Theory comes with a built-in constituency and a built-in opposition. Yet the evidence does point strongly to farming--and fairly strongly to fertilizer--as the culprit.

First of all, environmentalists are right to look at farms first. Whether city dwellers appreciate it or not, farming is by far the most drastic change people have made to the midwest--Chicago is just a pimple on the landscape compared to fields of corn and beans. If the Mississippi is now delivering two or three times as much nitrogen to the gulf as it did in 1940--and it is--those fields out beyond the sidewalks are an obvious place to look for the reason.

Second, their hunch does indeed seem to be right. According to Donald Goolsby of the U.S. Geological Survey, the heavily farmed and heavily fertilized upper Mississippi valley--which includes most of Illinois and Iowa--drains just 15 percent of the Mississippi basin, but contributes a whopping 51 percent of the nitrogen in the river. A similar disproportionate effect--which points directly at agriculture--shows up at every level, from smaller watersheds down to individual fields. Mark David of the University of Illinois' Department of Natural Resources and Environmental Sciences is preparing a "nitrogen budget" for the state. His figures show that the Embarras River watershed, just south of Champaign-Urbana (where farming takes up virtually all of the land), drains 0.015 percent of the total Mississippi drainage area but contributes 0.1 percent of the nitrogen in the river--seven times more than you would expect. Carefully metered experimental fields at Purdue University's Water Quality Field Station outside of West Lafayette, Indiana, confirm this circumstantial evidence with measurements: the typical midwestern corn-soybean rotation lost four times more nitrogen over a two-year period than a control plot planted with native big bluestem prairie grass.

Case closed? Not quite. What we put into the river isn't necessarily what shows up in the Gulf of Mexico. Different inputs follow different routes to New Orleans and may get chemically changed or detained along the way. For instance, city sewage-treatment plants and industries--known in the trade as "point sources" of pollution--account for perhaps 3 percent of the nitrogen humans add to the environment in the Mississippi basin, according to Goolsby. But he says they might be responsible for as much as 25 percent of the nitrogen that's ultimately delivered to the gulf because, unlike fertilizer, their "contribution" goes straight into the water rather than percolating through the soil, where it may be chemically changed or bound up (and therefore unavailable to nourish either corn or algae).

Third, environmentalists seem to be right about the timing of the changes. In 1970 the Mississippi River near the gulf carried roughly the same amount of nitrate (the most common form of nitrogen in the river) as it did in 1905. Around 1970 those levels started to go up, peaking around 1980 at about double the earlier amount and remaining there. On a graph this sequence looks like a steep slope up to a high plateau. Whatever is causing hypoxia in the gulf should have a graph that looks about the same. Midwestern fertilizer use doesn't exactly match this chart, but it's pretty close--climbing dramatically since 1950, doubling since 1970, peaking around 1980, and holding steady or declining a bit since then.

Of course none of this proves causation. It could just be coincidence.

Fertilizer is by far the biggest single source of nitrogen going into the Mississippi. But midwestern farmers have added to nitrogen levels in other ways too.

Most farmers devote most of their land to growing annual crops such as corn and soybeans. Unlike trees and prairie grasses, these crops are in the ground only from May to October. The rest of the year there's nothing to take up the nitrogen that soil microorganisms will happily go on producing as long as the soil is above 50 degrees. (In preagriculture days trees and grasses would have absorbed nitrogen year-round, a fact that has interested Purdue agronomist Sylvie Brouder in the possibility of growing off-season cover crops to take up the extra nitrogen.) Legumes such as soybeans, with the ability to fix their own nitrogen dinner from the air, are natural. But having millions of acres of them is not; their remains are another source of nitrogen.

Less obvious to outsiders is the drainage tile--now plastic pipe--that midwestern farmers have laid in the past 140 years under 50 million acres of land in the U.S. About 10 million of those acres are in Illinois--over a quarter of the state. In much of eastern Illinois and western Indiana, where traffic now speeds down interstates 57 and 65, the land was a nearly impassable swamp before it was drained. Elsewhere tiling serves a less dramatic purpose: it dries the soil faster in the spring. Without that help, much of the midwest couldn't be planted until June--at significant cost to the corn yield. (The old farm saying was that planting anytime after May 1 cost "a bushel a day for delay.") By speeding water off the soil, drainage tile also speeds up the loss of nitrogen, which might otherwise stick around to be denitrified by bacteria into biologically unavailable forms or to be taken up by the crop. Says Purdue agronomist Ron Turco, "Nitrate is the problem created by tile drainage." He acknowledges that managing the output of the tiles would be "a whole new concept" for farmers.

Finally, the physical structure of the Mississippi River itself has changed. At the Louisiana end almost a third of the "Mississippi" now takes a shortcut to the gulf via the Atchafalaya. "That's the same amount of water that is discharged by the River Nile," notes Illinois State Water Survey chief Derek Winstanley. He adds that the Atchafalaya used to dump its sediment and nitrogen load into a lake that's now almost full--so, beginning in the 1970s, it began sending significantly more of both into the gulf.

Of all the arguments farmers use to suggest they're not the culprits, only the Atchafalaya theory seems credible. They also blame nitrogen from human wastes, car exhaust, and industrial pollution, but these matter relatively little by Goolsby's accounting. And as for lawns and golf courses, forget it. Their owners apply fertilizer at higher rates than farmers, but they don't cover anywhere near enough ground to make a significant difference. U. of I.'s Mark David found their contribution to be negligible in Illinois.

Rabalais and Turner carried on their hypoxic-zone research in relative obscurity until 1993, when the Mississippi flood put it on the map. That summer the size of the zone doubled, which wasn't too surprising. The shocker came afterward--the zone didn't shrink back to preflood levels in the summers of 1994 or 1995 or 1996 or 1997.

Seeing another jumbo hypoxic zone in 1994 was enough for attorney Melissa Samet of the Sierra Club Legal Defense Fund (now the Earthjustice Legal Defense Fund). In January 1995, ten years after Rabalais and Turner made their first survey cruise, Samet--acting on behalf of 18 environmental, social-justice, and fishery groups--asked the U.S. EPA to get serious about the hypoxic zone. The agency declined to convene an interstate management conference, but its Gulf of Mexico Program has been working on the matter. Last year it formed a Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, which has met twice and has enlisted the White House's Committee on Environment and Natural Resources for a scientific assessment. State Water Survey chief Winstanley is representing Illinois on the committee. Illinois agricultural and environmental agencies have also begun conducting their own assessments of nutrients and sediment in Illinois waters. Both state and federal groups are expected to have something to say by fall.

What should they say? "Any industry should always seek to operate in the most socially and ecologically responsible manner," replies environmentalist Rob Moore, executive director of the Central States Education Center in Champaign; he also runs an E-mail discussion list on midwestern river issues. "If you are causing problems downstream, as a conscientious landowner you should be doing all you can to mitigate those damages." Sandra LaBlanc of the National Catholic Rural Life Conference recently put the same thought another way in U.S. Catholic: "How do you put a price on 355,000 fish killed?"

Putting a price on things may not be easy in theory, but in effect we do so every day by making choices in real life. Most parents would give all they own to save their child; assuming hypoxia did those fish in, would you give $500 for those 355,000 lives?

In other words, the question has to be asked: how much does the hypoxic zone matter? No fix is likely to come free. What makes the question harder is that midwestern farmers don't pay the downstream costs of their current way of farming, and environmentalists and gulf fishermen won't pay the costs of the farmers' farming differently. Each side is free to claim that its own needs are absolute.

Samet wants a "nutrient reduction control strategy" to be "aggressively" implemented as soon as possible. "We recognize that reducing nutrient loading into the Mississippi River will not be without cost," she told a hypoxia workshop in Anaheim, California, last fall, "but the environmental, water-quality, and health benefits to each person within the Mississippi River watershed, and to the Gulf of Mexico and those who depend upon its bounty, will be enormous."

That's easy to say when someone else is footing the bill for the reductions. The serious question is, how "enormous" would she think the benefits were if the aggressive control measures consisted of requiring her law office to cut its use of paper in half or to make copies only between 4 and 5 PM?

Speaking on behalf of farmers, Terry Francl of the American Farm Bureau Federation in suburban Park Ridge urges patience rather than haste: "There's a real legitimate scientific research issue here that should be pursued. But it's going to take lots of money and years of research--I emphasize the plural."

That too is easy to say when someone else is footing the bill for the status quo. Would he be willing to spend years achieving scientific certainty before acting if the problem were that Illinois fields were being poisoned at random?

State Water Survey chief Winstanley has done his best to make sure that the national hypoxia study assesses costs and benefits carefully. But he prudently stops short of saying how they should ultimately be weighed against each other: "We put both sides forward--and let the public and decision makers decide."

Cost-benefit analysis is a must for keeping the discussion honest, but at the extreme it can produce nonsense. According to Iowa State University's Agro-Oceanic Nutrient Flux Center, Mississippi-basin agriculture is a $100 billion-a-year business; gulf fisheries bring in only around $3 billion. If these easily measured short-term dollars were all that mattered, it would be cheaper to farm the midwest to the hilt and sterilize the entire Gulf of Mexico. ADM could pay off all the fishermen and still be ahead, right?

That kind of absurd logic can be turned against agriculture too. According to the Statistical Abstract of the United States 1997, the construction industry produced more than $500 billion in buildings, roads, bridges, and utilities in 1992, while farm output totaled less than $200 billion. If easily measured short-term dollars were all that mattered, we should pave every field. But you can't eat a parking lot.

The Farm Bureau's Shauman and Francl are anxious to maintain agricultural production in the midwest. If enough Americans agree, then at some point we may choose to conserve prime midwestern farmland--in effect sending would-be suburbanites and their houses and malls back to the city (or back to some place like Boston, which has a less fertile hinterland). If that ever comes to pass, it will not be a purely financial decision. For the same not purely financial reasons, we may also find it prudent to farm the midwest in a way that will not make the Gulf of Mexico fishery go haywire the way Lake Michigan's has. ow

Art accompanying story in printed newspaper (not available in this archive): illustration by Slug Signorino.

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