Farmers and lawn care companies in the Midwest use fertilizer to grow better crops and greener lawns. But excess fertilizer is washed downstream by rain, eventually reaching the Gulf of Mexico. Scientists say once in the Gulf, it triggers a process that causes a so-called ‘Dead Zone.’ The Great Lakes Radio Consortium’s Lester Graham reports:
Farmers and lawn care companies in the Midwest use fertilizer to grow better crops and greener
lawns. But excess fertilizer is washed downstream by rain, eventually reaching the Gulf of
Mexico. Scientists say once in the Gulf, it triggers a process that causes a so-called ‘Dead Zone.’
The Great Lakes Radio Consortium’s Lester Graham reports:
To get better crop production farmers use anhydrous ammonia to increase nitrogen levels in the
soil. To get greener lawns, homeowners use fertilizers that also can increase nitrogen and other
nutrient levels. But excess nitrogen gets carried away by rainstorms. For all or parts of 31 states,
that nitrogen is washed into ditches and creeks and rivers that are all part of the Mississippi River
basin. All of that land drains into the Mississippi and the Mississippi drains into the Gulf of
Tracy Mehan was the U.S. Environmental Protection Agency’s Assistant Administrator for
Water. Mehan points out that’s a lot of runoff that ends up in one place…
“It affects most of the inland drainage of the United States from Minnesota, from Ohio, from
Nebraska, Missouri, Iowa, Illinois all the way down to the Gulf of Mexico. So, we’re dealing
with a tremendously broad system here and with tremendous challenges to protect the Gulf of
Challenges because the nitrogen and other nutrients cause a problem.
Nancy Rabalais is a professor with the Louisiana Universities Marine Consortium. She says the
nitrogen causes a huge bloom of algae…
“Well, the nutrients stimulate the growth of plants just like fertilizers stimulate the growth of a
corn plant. But the plants in the Gulf are microscopic algae.”
Some of the algae is eaten by tiny aquatic animals and fish. But, with a huge algal bloom… some
of it just dies and sinks to the bottom. Those algae cells are consumed by bacteria that also
consume oxygen. Rabalais says that depletes the oxygen in the surrounding water…
“So what basically happens is that the production of algae is just too much for the system to
This oxygen starvation is called hypoxia. Marine life can’t live in a hypoxic area. Fish avoid it if
they can by swimming away. Other life that can’t move that fast dies. The size of the hypoxic
zone varies from year to year. Weather across the nation affects the amount of runoff that ends
up in the Gulf, but the trend has been a dead zone that’s gotten bigger over the past twenty
years… and according to Rabalais’ research it has doubled in size since the 1950’s when nitrogen
started being used extensively in agriculture.
(sound of boat engine starting up)
In Louisiana, the commercial fishers and shrimpers are concerned about the ‘dead zone.’ Some of
the smaller operations find it difficult to travel the longer distances to find fish outside the ‘dead
Nelwyin McInnis is with the environmental organization, the Nature Conservancy. Walking in a
marsh area in Louisiana, she talked how important it was to that region that farmers and
homeowners in the Midwest do something to try to cut back on the amount of fertilizer that ends
up in the Gulf of Mexico.
“Certainly any ways that you can reduce the fertilizer runoff would certainly be of value. And I
know each farmer can’t imagine their impact hundreds of miles away in the Gulf of Mexico, but
each one adds up and has an effect.”
But powerful agricultural interests say the ‘dead zone’ in the Gulf of Mexico is not caused by
nitrogen fertilizers in the farm belt. The American Farm Bureau has kept up a steady campaign
of denial of responsibility. Reports and essays published by the Farm Bureau question researcher
Nancy Rabalais’ findings. Rabalais says the Farm Bureau can question her all it wants. Her
published work has been reviewed by other scientists in close to a dozen major scientific journals.
“We don’t believe in collecting data and putting it on a shelf. We get it to the scientific public and
we also try to translate it so that the public, including the agricultural community can understand
what it’s saying.”
Whether the agriculture community wants to hear what those data are saying is another question.
However, the government is taking it seriously and is looking at ways to reduce the amount of
nutrients being washed into the Gulf of Mexico.
For the Great Lakes Radio Consortium, this is Lester Graham.