Code Red: Mississippi River Under Nitrate Attack
WHY YOU SHOULD CARE
Because one of the most important bodies of water in the world is in danger. And you probably haven’t even heard about it.
By Anne Miller
What happens when filters get clogged — like your air-conditioning filter, your car filter, your coffee filter? You clean them out. But what happens if the filter is an entire ecosystem? How do you clean out one of the world’s largest river systems when it’s clogged?
We’re talking a filter that spans some 2,300 miles, and the sources of the stuff clogging the filter lie so far away from the places feeling the impact that it’s hard for one to see the other.
The Mississippi River is home to bacteria that naturally filter out things like nitrates before they reach the Gulf of Mexico. Nitrates, commonly used in fertilizers on Midwestern farms, drain into local streams, which feed into the big river — which ends in the Gulf. Today, the Gulf, like many other large water bodies, suffers from dead zones — areas in the water where few fish live.
These things are not unconnected. And a new study links them even further.
Almost 100 percent of the Mississippi River’s water passes through areas that should filter out the water’s nitrates before they can reach the Gulf. But a new study by hydrogeologists at the University of Texas at Austin found that the natural nitrate filtration system is overwhelmed. Nitrates are going into the water — and they’re staying in the water.
“Clearly, for all this nitrate to make it downstream tells us that this system is very overwhelmed,” says professor Bayani Cardenas of UT, who co-authored the study.
Nitrates are naturally occurring, but they also come from things like runoff from farm pesticides. And Americans have greatly altered the landscape that feeds into the river, from building levies to living on wetlands to creating drains for field runoff.
“Whatever capacity you have there for those micro-organisms to uptake or transfer the nitrogen is already being utilized,” says professor Aaron Packman of Northwestern University outside Chicago. Meaning: There’s a nitrate overdose in our soil and among our plants. How do we fix this?
Packman calls it a political problem: Farmers need to farm and Americans need to eat. Plus, it’s understandably difficult for an Illinois farmer struggling to make his farm productive to care about fish dying off half a continent away.
He says the way the river becomes more nitrate-filtering is to reclaim those natural systems: Restore wetlands and “reconnect floodplains to the river systems.” But he — and we — know that this leaves a lot of political work to be done.