Restoring Nature’s Water Filter: How Streamside Vegetation Can Save the Gulf of Mexico

(Reprinted from the Environmental News Network):

Back in 2003’s Global Environment Outlook Year Book, the United Nations Environment Programme (UNEP) declared the ocean’s “dead zones” the world’s top emerging environmental challenge. Now a recent report by UNEP says the number of dead zones, or low oxygenated areas in the world’s oceans, may have now grown to as many as 200, up from an estimated 150 in 2003.

Spreading dead zones have more than doubled over the last decade and are becoming the leading threat to commercial fisheries. The most well-known dead zone is in the Gulf of Mexico. Its occurrence has been directly linked to nutrients or fertilizers brought to the gulf by the Mississippi River.

Each summer, following spring flows from the Mississippi, the Gulf of Mexico experiences a massive die off of bottom-dwelling creatures like crabs and oysters, and sees an exodus of shrimp and fish from traditional fishing grounds along the coast. Scientists say the source of the Gulf’s now 8,000-square-mile dead zone is a condition of low oxygen levels, called “hypoxia,” largely caused by an influx of excess nitrogen from farm fertilizers, sewage and industrial pollutants.

U.S. Energy Policy and Dead Zones

In early 2008 scientists predicted the Gulf Dead Zone could grow to a record 10,000 square miles. The reason? According to the June 12, 2008 issue of U.S. News and World Report, U.S. farmers, encouraged by ethanol mandates and higher commodity prices, have expanded corn plantings and driven the acreage of other crops to record levels. Farmers along the Mississippi Valley are using more fertilizer, which contains nitrogen and phosphorous. These chemicals, when not used by crops, often find their way from farmland into water. Corn, because of its shallow roots, tends to be quite “leaky.” Excess nutrients lead to increased algal production and increased availability of organic carbon within an ecosystem, a process known as eutrophication. As the algae die and decompose, they consume oxygen, suffocating everything from clams and lobsters to oysters and fish.

Restoring Nature’s Water Filter

In July 2008 Hurricane Dolly stirred the gulf waters keeping dead zone expansion to a minimum. Scientists are testing floating, wave-powered pumps, designed to mimic the stirring effects of hurricanes. While these technologies may be of some use, Trout Headwaters, Inc. (THI), a private aquatic restoration firm based in Livingston, Mont., advocates a simpler, yet still challenging approach: Implementing policies and devoting our collective energies toward restoring and protecting nature’s own, perfect, water filter.

THI has worked with the U.S. Army Corps of Engineers and others to demonstrate improved, vegetative approaches to stabilizing and restoring streams and rivers in the Mississippi Delta. THI is dedicated to the development and application of state-of-the art technologies and treatments for restoring critical streamside or “riparian” vegetation. Healthy riparian vegetation acts to filter harmful pollutants, sediments and excess nutrients that wash into waterways from agricultural fields and urban areas.

Louisiana State University geologist Paul Kemp said in a National Public Radio interview that excess fertilizer wouldn’t be a problem if the Mississippi, and many of its tributaries, were still connected to their natural floodplains. The genesis of the Gulf’s dead zone was trying to control Mississippi flood waters, said Kemp, pointing out that, “Levees were built from almost the first day the Europeans set foot in Louisiana, so that means the modern river is well-separated from its delta.” After viewing many of the streams and rivers in the Mississippi Delta, THI President Michael Sprague agrees that the severe alteration of these stream channels is a serious, regional problem, and is troubled by an overuse of hard armor “riprap” lining many of those channels, which doesn’t offer the same benefits as trees and shrubs.

“Stream channelization, or straightening, and levee building has been rampant in the Lower Mississippi Alluvial Valley,” explains Sprague. “While this was done in an attempt to decrease flooding, the side effects have been more significant than we could have imagined.”

Healthy Riparian Vegetation Slows and Filters Runoff

Streams and rivers are meant to slowly meander and periodically overflow their banks in a complex hydrologic cycle of erosion and deposition. The problem, says Sprague, is the filter nature designed – diverse, streamside, woody vegetation that slows and purifies water before it enters streams and rivers – has been stripped from thousands of miles of Delta streams to make way for agriculture and development. The U.S. Department of Agriculture reports the Lower Mississippi Alluvial Valley has undergone the most widespread loss of bottomland hardwood forests in the United States. In Mississippi and Louisiana the U.S. Fish and Wildlife Service estimates more than 60 percent of native bottomland forests have been cleared, impacting many species of wildlife which once thrived in these floodplain ecosystems.

“When you combine channelization and levee building with the removal of riparian vegetation and bottomland forests, then throw in hard armor riprap lining stream banks, intensive agricultural practices that farm right up to the edge of streams, and ill-planned urban development, you get an ecological disaster like we’re seeing now through the Mississippi Delta and in the Gulf,” says Sprague. “This scenario has been repeated all over the world, and I applaud the UNEP for recognizing that unless we restore the health of our streams and rivers, not only will we see the collapse of freshwater and marine fisheries, like in the Gulf Dead Zone, we’ll begin to regret having squandered this country’s abundant supply of clean drinking water.” 

Besides designing and installing more than 400 stream and wetland restoration projects across the U.S., Sprague’s company has completed several successful demonstrations of “green technologies” for river restoration and bank stabilization in the Mississippi Delta. “I’m hopeful we can turn things around. Now we know better so we’re doing better, and that’s half the battle,” said Sprague.

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