National Geographic News
Canals hold pipelines that deliver oil and gas from offshore wells.

Canals crisscross the Mississippi River Delta near Golden Meadow, Louisiana, where nutrient pollution remains a problem.


Brian Clark Howard

National Geographic

Published April 11, 2014

U.S. federal scientists say water quality has declined in the massive Mississippi River Basin in recent years due to the combined effects of agricultural and urban infrastructure, despite decades of conservation efforts. That's a concern both for those who rely on the river system and for those downstream on the Gulf of Mexico, where a huge "dead zone" hurts fishing and recreational opportunities.

Scientists with the U.S. Geological Survey (USGS) sampled the main stem and four tributaries of the Mississippi River and found that levels of nitrate increased at more than half the sites from 1980 to 2010. Overall, nitrate levels increased by 14 percent during that period, the USGS reported in a congressional briefing on Capitol Hill Friday.

The new findings are a warning about water quality health nationwide, and raise a troubling issue: even when policymakers and environmental advocates try to clean up the waterways, their efforts are not always successful.

Scientists often focus on levels of nitrate because it plays an important role in the environment. The nitrogen in nitrate is an essential nutrient for plants. But too much of it leads to overgrowths of algae, called blooms, which can use up too much oxygen in the water (a process called eutrophication), choke out fish and seagrasses, and in some cases release toxic chemicals.

Large algal blooms have created dead zones in Puget Sound, the Chesapeake Bay, Long Island Sound, and many other waterways. The Gulf of Mexico is now host to the world's second largest dead zone, a patch of impaired sea about the size of New Jersey. (Learn more about river basins.)

"When oxygen gets too low, most fish can't live there," says Nancy Rabalais of the Louisiana Universities Marine Consortium, who studies the dead zone. "They'll swim away if they can, but if they are associated with the bottom they can't." She points to declines in shrimp catches and charter fishing trips in the area and an estimated loss of $82 million a year.

The Mississippi Basin is a good representative of the rest of the country because it has mixed urban and agricultural areas, and because "many lessons learned there can be applied throughout the U.S.," said Lori Sprague, a hydrologist with USGS's National Water-Quality Assessment Program, at the hearing.

Across the country, more than half of the streams and rivers are in "impaired condition," meaning swimming and fishing are not advisable, reports the Environmental Protection Agency.

Rising Tide of Nitrates

Sprague said that although data from decades ago are limited, available numbers show that since the 1940s, nitrate levels skyrocketed in the Mississippi Basin, from less than one million tons of input to about 13 million tons by the mid 2000s. The biggest sources are industrial fertilizers (41 percent) and animal manure (10 percent), followed by urban areas (7 percent), wastewater treatment (7 percent), and other sources.

The decades since the 1940s represent the maturation of the "Green Revolution," when agricultural productivity in the basin increased 400 percent, says Colin Wellenkamp, the director of the Mississippi River Cities and Towns Initiative for the Northeast-Midwest Institute in Washington, D.C.

Studies now show that about 16 percent of the nitrate in fertilizer is not taken up by the crops to which it is applied, Sprague said at the hearing. Instead, it runs off fields and makes its way into ground or surface waters.

Fertilizer use on farms began to plateau around 1980, and over recent years many farmers have been applying smaller amounts of chemicals, thanks to stronger formulations and the rise of "precision agriculture," in which more targeted applications are made. The same trend has persisted on many golf courses and other landscaping efforts.

Still, from 1980 to 2010, the biggest gains in nitrates were seen in the upper Mississippi and Missouri River Basins, especially in Minnesota and Wisconsin, which saw increases of 50 percent. Parts of Illinois and Iowa saw decreases in nitrates during that period.

Conservation Measures?

Sprague said the data are unable to show exactly what effects are responsible for the changing nitrate levels. Modeling shows that conservation measures decrease nitrate levels, but in the real world, many factors are at play, including population growth, urban sprawl, changes in livestock operations, switching crops from soy to corn (which uses more fertilizers), and conversion of marginal land to cropland to support a booming corn ethanol market.

For its part, the EPA has called for a 45 percent reduction in nitrate levels in the Mississippi Basin. "As a result, governments are increasing their efforts, and each state is developing a reduction plan, involving working with stakeholders to voluntarily reduce inputs," said Sprague.

In addition to measures taken on farms, many improvements have been made in wastewater treatment plants and in management of industrial sources of pollution. In general, such "point sources" of undesirable chemicals have been well managed since passage of the Clean Water Act in 1972, said Sprague. Management of "nonpoint source" pollution, such as runoff from farms, lawns, and roads, has been more difficult, although there has been progress made, such as discouraging fertilizing before rain and adding filters to stormwater runoff systems.

Suzanne Bricker, a physical scientist who manages the National Estuarine Eutrophication Assessment for the National Oceanic and Atmospheric Administration (NOAA), told the hearing that one positive case story is Tampa Bay, Florida. Since 1980, nitrate levels in the bay have dropped by 60 percent, leading to a significant restoration of the seagrass beds that fish depend on. That success was achieved by improvements to wastewater and stormwater treatment and efforts by the chemical industry to reduce spills.

David Helvarg, the executive director of the environmental advocacy group Blue Frontier Campaign, tells National Geographic that the federal government should take a stronger role in requiring nutrient reductions. The feds should set mandatory targets for each state, and then let local leaders do the implementation, he says.

Helvarg points to efforts taken by farmers in Illinois and Iowa to lessen runoff, including reducing the amounts of fertilizers applied and planting native vegetation around fields. In Florida, county governments have encouraged people to fertilize their lawns more selectively, in an effort to protect the fragile Indian River Lagoon.

But we need to move beyond voluntary efforts, he says. "We need to stop subsidizing agriculture for putting fertilizer on fields, because all that surplus just follows gravity down to the Mississippi, and then you are growing that second crop of algae."

Many efforts have involved public education, including telling people not to pour things down storm drains, to pick up after their dogs, and to avoid littering. "It took 20 or 30 years for people to figure out if they smoke they'll get cancer and if they don't put on their seatbelts they'll go through the windshield," says Helvarg.

Still, Bricker said that when it comes to the health of estuaries, "they would probably be a lot worse if we hadn't implemented management," given rising population and development.

Lessons From Pesticides

Sprague said better labeling and control of specific pesticides, such as metolachlor and diazinon, has resulted in measurable decreases in the chemicals in the Mississippi. That proves conservation steps can clearly have an impact, she noted.

Still, there is often a lag, even as long as decades, in observable results and changes on the surface because water takes a long time to migrate through the ground.

It is partly for that reason that about 57 percent of streams in agricultural areas and 83 percent of streams in urban areas still have pesticide levels that exceed EPA guidelines for aquatic health. About 10 percent of agricultural streams and 7 percent of urban streams show pesticide levels above EPA guidelines for human health.

To better understand and manage America's waterways, more long-term monitoring of water quality is needed, said Sprague. She added that the USGS has recently begun tracking salinity, dissolved oxygen content, carbon content, and other variables.

Alan Vicory, the chair of the Water Environment Federation's Government Affairs Committee, said at the hearing that monitoring is as fundamental for science as it is for health care. "Who hasn't had their blood pressure taken?" he asked. "That's monitoring, which is key to making decisions."

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Mallimodugula Bhaskar
Mallimodugula Bhaskar

On land fertilizers are 'resources' to grow more food but in water the same fertilizers are 'pollutants' that cause dead zones.

Farmers benefit from fertilizers, but fishers suffer due to them, why is this ?

What would happen if farmers used fertilizers to grow weeds, instead of grass and grain.

How to grow grass and grain in waterways using the fertilizers available for 'free'.

Fishers should thank farmers for providing them with 'free' fertilizers, instead of complaining that the fertilizer is killing fish.

Harold Reetz
Harold Reetz

I am concerned about the anti-agriculture tone of this article.  Fertilizer use and crop production data from the Midwestern states clearly show that farmers have in fact taken major action to reduce potential nutrient losses from their fields to the Mississippi River and the Gulf of Mexico.  Total nutrient application per acre has been steady or reduced in most states, even when manure use is included.  Balance of nutrients shows that over the past 20 years, most of these states have removed more nutrients (N, P, and K) than have been applied in fertilizers and manures.  When computed on the basis of total grain production, these data show substantial improvement in nutrient use efficiency.  This has been accomplished through improvement in the technologies of crop production systems, including use of precision farming tools, more efficient genetics of major crops, and better fine tuning of management to match nutrient applications to crop requirements.  The 4R system of nutrient management---right nutrient sources, right rate, right placement, and right time---has been used as a guide in recent years to match nutrient use to the bets research available.  Unfortunately, this major improvement in management and nutrient use efficiency has not resulted in as much impact on reducing the hypoxic zone as we would expect.  This might be an indication that fertilizer use per se is not the major contributor to nutrient loading that it has been claimed to be.  In any case, farmers continue to work toward improving nutrient use efficiency, to do as much as they can to reduce their contribution to water quality problems.  It is in fact an economic benefit to them to do so, because lost nutrients means lost investment in the nutrients they must purchase to grow crops.

Another concern is the common criticism in National Geographic publications and other popular press of the use of feed grains for producing ethanol.  Ethanol from grain is a renewable fuel that contributes to reduced air pollution compared to other fuel sources and helps reduce our dependence on imported oil.  We in fact use only a small part of our Midwest grain production for human food.  Most goes for livestock feed, either domestically or in exported grain for feeding livestock in other countries.  Very few people would be interested in using our corn and soybean crops directly for human consumption.  

Another myth commonly presented is that we could do better by shifting to organic production systems.  Our commercial fertilizers are much more efficient and more easily managed to prevent pollution than organic systems.  In fact, organic nutrients cannot be used by crops until they are converted to mineral nutrients---the same as our fertilizer nutrients.  And the reduced productivity of organic systems would mean that shifting our production systems to organic would mean converting more of our natural forest and grasslands to grain production, more use of our precious water supplies for irrigation, and more production on marginal lands that are inefficient and more erosion prone.

We need to thank our farmers and agribusinesses for their ongoing efforts to continue to provide the world with the most abundant, safest, and cheapest food possible, while at the same time minimizing negative impact on natural resources.  The world will be fed, and energy from agriculture will be produced by continuing to employ the best technologies and management systems we can devise.  Fertilizer use will have to continue to increase, but it will be accompanied by more efficient management and better genetics.

I would like to see National Geographic  and other publications give a fair analysis of this issue and the effective steps agriculture is taken to be a positive force.


Waste treatment plants along American rivers are not operated properly more so today with it's relaxed Regulations and lack of inspections due to financial cuts and political wim of the Right.

Hector Prieto
Hector Prieto

El Agua es la fuente de vida en este planeta.  Entonces por que la contaminamos con excremento y desechos? Sin agua, este planeta ciertamente morira igual que todos los que en el habitamos.  

Sprague said that although data from decades ago are limited, available numbers show that since the 1940s, nitrate levels skyrocketed in the Mississippi Basin, from less than one million tons of input to about 13 million tons by the mid 2000s. The biggest sources are industrial fertilizers (41 percent) and animal manure (10 percent), followed by urban areas (7 percent), wastewater treatment (7 percent), and other sources.

Harry C.
Harry C.

It is amazing to me that the American public doesn't readily accept the fact that humans are destroying their environment. But, that is really only a small portion of the planet. The rest of the world has the same problem. However, we must remember that in many poorer nations growing crops to feed their populace is essential. Fertilizers are necessary evils there. It would be interesting if genetic alteration in food crops could repel insects and eliminate the use of fertilizers. 

I live in a community surrounded by livestock, corn and soybean fields. We have a man made lake and have banned use of certain lawn fertilizers. But the runoff from the farms into the streams that feed our lake are full of nitrates. Last year the lake was closed because of algae blooms. We also have to deal with the insecticides sprayed from airplanes. 

 I often wonder what the world will be like for my grandchildren if mankind doesn't take steps now.  

angelo c.
angelo c.

Not until we have cut down the last tree, plucked every fish from the sea and poisoned every last river will we realize we cannot eat money.

As long as there is some money to be made by somebody, the environment will always take a back seat.

It's too late to do anything but maybe slow down our eventual self infliction of demise.

Even if we were to totally halt in an instant our destructive assault on the environment, it would take hundreds of years for the planet to show signs of any recovery.

Massive continental size of plastics floating and growing in the oceans, increasing formation of dead zones in our lakes and oceans, increasing levels of particulate matter in our air, confirmation of increasing levels of PCB's and heavy metals in extremely remote parts of our Arctic and Antarctic oceans and its native wildlife etc, ec, etc.

The Mississippi Basin is just a little tiny drop downstream of a much larger, global's not even a problem because problems have solutions and as pessimistic as it sounds, it is irreversible.

The only hope we have is to ingrain future generations the value of life and devalue the importance of amassing wealth and to de-globalize this farse of the  economy and hope the growth of this "new culture" outpaces the development of our current culture...and we all know that ain't gonna happen...

Have a wonderful day (cough, cough, spit, spit, cha-ching!)

Bob Perry
Bob Perry

There are only eight monitoring sights from the upper Mississippi River to the Gulf. That is not monitoring. There is no monitoring of nitrate in the Gulf of Mexico.  These people are not serious about finding out how and when nitrate levels rise in the Gulf and proving or disproving their hypothesis that nitrate is the problem. There is scientific instrumentation that could monitor nitrate real time and be very affordable.  The EPA scientific advisory board spent 11 years studying the theories and concluded that it was not just nitrate. A larger problem is the disposal of dredge material into the ocean by the Corps of Engineers.  That sediment should, as the state of Louisiana has requested, be put onto land.

Rodolfo Alonzo
Rodolfo Alonzo

I find this story very disturbing. Humans are the most destructive forms of life hands down. Subsistence living went out with the cowboys and Indians. I just put out some weed and feed on my lawn to kill dandelions. Not amphibians, wildlife, rivers.

Tu Fur
Tu Fur

@Harry C.
, Not all is as it appears in print. Since the EPA came into effect, much has been cleaned up. I can walk Los Gatos or San Jose Creeks and see the business drainage redirected. In the same day, I can walk Boulder Creek in Santa Cruz Co. and point out the raw sewage coming from summer cabins now used as year round homes. You have to chill. Real people are doing the best they can. Be part of the pressure on the country and city governments where you live. Take samples for a local University professor. Just stop sounding like the hordes of neo-alarmist. Please.

Gwendolyn Mugliston
Gwendolyn Mugliston

@angelo c.  you are so absolutely correct.  It seems to me if we all became Buddhists we migjht fare better.  Perhaps not Buddhist in name but buddhist by nature and figure out for everything we do what is the path of least harm.   Maybe this is why the white man hated the Indians so much.  Indians were dangerous and had dangerous "thoughts" and might contaminate the masses. 

Your second to last paragraph of devaluing the importance of amassing wealth is so very right.  It seems our woes and future demise is and will be associated with pride, fear, greed, lust and envy.  

Maybe the human species has a gene that comes into action when only the avaricious 1% become dominant and we just commit global suicide by self self immolation.

Sigh.  Some humans can be so fantastically generous and humane.  Why not all?  

David Seabaugh
David Seabaugh

@angelo c. @Gwendolyn Mugliston. We greedy, polluting, lusty, envious, wealth amassing Americans export 90 million pounds of grain alone every year. Most of it goes to the worlds poorest people and a large percentage of it is free. Yes, greedy Americans literally feed the world. If we took your advice and shut down our large wealth amassing farms and factories, the environment might be a little cleaner, but at what cost? Where is your Buddhist empathy for all those who would starve to death without our generosity?

Also, I happen to live in Louisiana and you will be happy to hear that our water quality is outstanding and fishing in the Gulf has never been better. To paraphrase Mark Twain; Reports of the death of the environment have been greatly exaggerated.


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