gulleyAn “ephemeral gulley” that carried soil and agrichemicals from an Iowa farm toward the Gulf of Mexico during a 2010 storm. Photo: Environmental Working GroupNancy Rabalais, marine scientist and executive director of the Louisiana Universities Marine Consortium, is probably our foremost authority on the vast, oxygen-depleted “dead zone” that rears up annually in the Gulf of Mexico, fed by fertilizer runoff from large Corn Belt farms. (I interviewed her for my podcast last year.)

In a report on the PBS Newshour blog, Rabelais delivers some bad news: Floods in the Mississippi River watershed this spring are washing tremendous amounts of fertilizer into Gulf, promising to generate the largest dead zone on record.

In addition to carrying in fertilizer runoff, the floods threaten to worsen the dead-zone problem by flushing in much more fresh water than normally makes it into the Gulf, PBS reports:

A surge of fresh water creates a layering effect in the seawater, which compounds the problem. The freshwater sits above the heavier saltwater, acting as a cap that prevents oxygen from reaching the deeper water levels.

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Agribusiness interest groups like to sow doubt about the cause of the annual dead zone by claiming that other factors, such as residential lawns, contribute more fertilizer runoff than agriculture. I obliterated that notion in this post last year.

The fact that heavy rains in the Midwest translate to the ruin of larger swaths of the Gulf fishery points to an uncomfortable truth about industrial agriculture: It makes us more vulnerable, not less, to the very weather shocks (e.g., severe flooding) that we can expect from unchecked climate change.  

What do I mean? Let’s start with the soil and end in the Gulf.

The Corn Belt in the Midwest remains one of the globe’s greatest stores of prime topsoil, even though we’ve sacrificed about half of it since settlers first started breaking ground there in the 19th century. Federal conservation programs began to dramatically slow high erosion rates starting around 1985, but the upswing in corn prices over the past few years has changed all of that. As the Environmental Working Group recently demonstrated in its report “Losing Ground,” high crop prices and perverse policy incentives have inspired farmers to squeeze their land to the hilt, leading to much higher erosion rates than the government acknowledges — especially when storms hit. According to the EWG report:

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In some places in Iowa, recent storms have triggered soil losses that were 12 times greater than the federal government’s average for the state, stripping up to 64 tons of soil per acre from the land, according to researchers using the new techniques. In contrast to the reassuring statewide averages, the researchers’ data indicate that farmland in 440 Iowa townships encompassing more than 10 million acres eroded faster in 2007 than the “sustainable” rate. In 220 townships totaling 6 million acres, the rate of soil loss was twice the “sustainable” level.

Among the triggers for soil loss are what EWG calls “ephemeral gullies” (pictured above), which “reappear rapidly” during storms where “farmers have tilled and planted over natural depressions in the land.” The gullies then “form ‘pipelines’ that swiftly carry away the water the earth cannot absorb” — and along with it, tons and tons of soil that’s been lashed with fertilizers and other agrichemicals. One can only imagine the long gashes that formed across farmland during this spring’s prolonged deluges.

And bad planting decisions aren’t the only thing that make land vulnerable to soil loss and agrichemical leaching. As I reported last year, University of Illinois researchers have found that over the long term, reliance on synthetic nitrogen fertilizers reduces soil’s organic matter content — making it less able to hold water and nitrogen.

So, a system hinged on fencerow-to-fencerow mono-cropping and synthetic chemicals leaves our nation’s most prized farmland extremely sensitive to heavy storms. And when those storms hit, we get yet more pressure on another highly productive and ever-besieged ecosystem: the Gulf of Mexico fishery. EWG puts the case pungently:

The runoff from vulnerable farmland not only washes away soil — the fertile legacy of thousands of years of geological processes — but also carries with it a potent cargo of fertilizers, pesticides and manure that flows into local creeks and streams and eventually into the Mississippi River. Ultimately it ends up in the Gulf of Mexico, generating the notorious dead zone — a zone of depleted oxygen that suffocates marine life when it forms each year.

So this is the system that swears only it can “feed the world” as global population approaches 9 billion over the next decade? Given that we can expect more, not fewer, severe storms going forward, it seems wise to consider a switch to practices that build resilience instead of depleting it: organic no-till farming, mixed cropping, widespread use of nitrogen-fixing cover crops, and the like. But that would mean a severe change in federal farm policy. As EWG reports, the policies now in place ensure more of the same:

Chronically underfunded voluntary conservation programs are failing to blunt the damage caused by federal policies that push farmers to plant crops fencerow to fencerow. Between 1997 and 2009, the government paid Iowa farmers $2.76 billion to put conservation practices in place. It paid out six times as much — $16.8 billion — in income, production and insurance subsidies that encouraged maximum-intensity planting, not conservation. Across the Corn Belt, the gap was even greater — $7.0 billion for conservation and $51.2 billion for income, production and insurance subsidies. The $18.9 billion spent to subsidize expansion of the corn ethanol industry, along with misguided federal mandates to produce increasing amounts of ethanol, further increase the pressure to intensify production.

The next farm bill, scheduled for debate in 2012, will take form under draconian budget conditions. Farm-state pols are already posturing to defend expensive production incentives (read: crop subsidies and ethanol goodies) and direct budget-slashing zeal in the direction of hunger programs. Conservation incentives, too, are on the chopping block. In other words, the current policy regime has mountainous weight behind it. All the more reason to organize now for a progressive farm bill. Stay up to date on farm-bill developments by following the National Sustainable Agriculture Coalition’s excellent blog.