Ask Eartha: What is the dead zone, and why is it growing? |

Ask Eartha: What is the dead zone, and why is it growing?

A streak of lightning lights up the pre-dawn sky in Gulfport, Mississippi, Thursday morning, Aug. 10. The dead zone in the Gulf Coast has gorwn to 8,776 square miles.
Tim Isbell / AP | The Sun Herald

Dear Eartha,

I recently heard a story about a dead zone in the Gulf of Mexico. It’s the first I’ve heard of it, and apparently it’s getting bigger. What is the dead zone, and why is it growing?

– Will, Frisco

I’ve also been reading stories about the dead zone, Will, so I’m really glad you asked about it! This is an interesting topic because, like many environmental problems, there are many interrelated issues at play, from agricultural policy and practices, to climate change and economics.

To begin, let’s start with the basics.

Almost all forms of life need oxygen to survive. We might get this oxygen in different ways — through lungs, gills or even skin — but without this wondrous gas, we’d be toast. The term “dead zone” is used to describe aquatic environments where life can’t exist because there isn’t enough oxygen. And as far as the Gulf of Mexico is concerned, lack of oxygen in the water is largely caused by agricultural runoff.

Animal manure and chemical fertilizers are the primary agricultural sources of excess nutrient pollution. Modern industrial farmers commonly plant season after season. This practice helps to maximize profit, but without a chance to replenish nutrients, soil loses its fertility. To make up for this, many farmers rely on inorganic chemical fertilizers to maintain high production levels.

Trouble is, degraded soils don’t hold as much water, and when it rains, both soil and their fertilizers are washed into our waterways. In America’s agricultural heartland, these chemicals end up in creeks and streams that eventually spill into the Mississippi River and the Gulf of Mexico. Plants love nitrogen and phosphorous, and the fertilized runoff is full of them. These simple elements feed algae, which bloom profusely in the well-nourished waters. Once the algae die, they decompose, and it’s this process of decomposition that robs the water of oxygen. Aquatic critters that can move will swim out of dead zones; others, like organisms that live on sea floors, will die.

This year, the Gulf dead zone is in the news because it’s larger than ever before. At 8,776 square miles, it’s the size of New Jersey. And scientists predict that, unless action is taken, the dead zone will continue to grow. Why? Because of climate change.

A study recently published in Science magazine predicts that the amount of nitrogen in U.S. waterways will increase 19 percent by the end of the century. In the Gulf, it could increase up to 24 percent. This is because climate change will increase total rainfall, which will simply wash more fertilizer downstream.

Dead zones can negatively impact local economies. Just think — if you’re a Gulf Coast fisherman who relies on a thriving ecosystem for an income, the dead zone could both decrease the total catch and increase your costs by making you travel further to find healthy fish. This could mean higher prices for consumers and the loss of jobs for fishermen. And some algal blooms are toxic to humans, impacting the drinking water supply.

It’s not just Gulf states that are at risk. Last year, an algae bloom forced the closure of half the Dungeness crab fishery in Washington state. Some Colorado rivers, like the Arkansas and the South Platte, struggle with water quality issues, including excess nutrients. Although we don’t have the levels seen in more polluted waterways, we can still be part of the solution. Here in Summit, you have options for planting your own garden, joining a farm share program or purchasing organic produce at farmers markets or grocery stores. By focusing on improving long-term soil fertility, supporting organic agricultural practices and purchasing locally produced food, we can lessen the impact of the industrial food systems that cause so much water pollution in America’s heartland. Visit to learn more about how you can decrease the environmental impact of your food choices.

Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at

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