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A Downward Spiral: Coastal Wetland Ecosystems One Month After Hurricane Isaac

3p Contributor | Wednesday September 26th, 2012 | 0 Comments

Hurricane Isaac enters Gulfport, MS

By Steven Apfelbaum

For the now-destabilized gulf coastal wetland ecosystems, a slow-moving hurricane with heavy rain and high, shoreline-pounding surf may be the most damaging type of storm. This is true especially around the mouth of the Mississippi River, which took a direct hit from Hurricane Isaac earlier this year. The storm surge associated with Hurricane Isaac showed firsthand the devastating effects that a long, slow hurricane has on fragile coastal ecosystems.

The storm surge associated with a hurricane wreaks havoc on the natural world around it, especially on storm protection buffers provided by nature, which take the form of barrier islands and buffers composed of wetlands and forests between the coast and coastal communities or cities. This powerful surge force topples trees, rips off wetland soils, especially floating mats of wetland vegetation, and introduces salt water into freshwater wetlands and the soils beneath these wetlands. Salt further destabilizes the muck and peat substrates, contributing to their further decline and collapse.

Many cities in India and other tropical country locations learned of the self-inflicted devastation created as mangrove ecosystems were removed for the timber resources and development. New Orleans and other U.S. gulf coastal cities need also to brace themselves for more intense and further exacerbated onslaughts from storms as these critical natural barriers are diminished in size and altered in their plant composition and durability—all of which essentially reduce the effectiveness of the buffers.

Forty-three percent of the lower 48 states are connected tributaries to the Mississippi River Basin. Currently, there is a coordinated effort over a vast area of the U.S. and a small portion of Canada to reduce nutrient loading and ensure that a balance of coarse-to-fine sediments enters the gulf. That means that primarily fine, clay-sized particles stay suspended in the moving river waters, and bigger sand, gravel and larger soil particles are captured behind dams on the river. Thus, only the finest soil fractions of clay-sized particles with the absorbed nutrients regularly make it to the gulf. This has to change if we intend to rebuild and protect our natural buffer areas.

In March 2012, the author flew over the ground conditions of the Gulf coastal wetlands from Corpus Christi, Texas, to Mobile, Alabama. This trip led to some startling observations, some of which were previously unreported and have no doubt worsened since August:

  • The storm surge does something more insidious that historically may not have mattered as much. Today, the nutrient-rich fine mud and associated chemically bound agricultural fertilizers from the Mississippi River and other watersheds gets re-suspended from shallow areas, where it has been deposited (for example, off the mouth of the Mississippi and Athachaflaya rivers). It is then carried by the storm surge into the coastal wetlands, where a blanket of this nutrient-rich mud of varying depths is deposited. In the gulf, these mud and nutrients contribute to the devastating gulf hypoxia risk occurring annually.
  • In locations west of the Athachaflaya River mouth, these types of mud have filled in former marshes, smothering productive marsh and other native coastal wetlands.  More so, the high nutrients encourage weeds, such as the aggressive non-native giant reed grass (also called Roseau cane, yellow cane, common reed, giant reed or Phragmites). While a native version of this plant did originally exist in the gulf coastal wetlands, the tall, dense stands, ranging from 15-20 feet tall, now forming over thousands of acres have the characteristics of the European invasive strain of this species. Many thousands to tens of thousands of invasive giant reed grass populations start from individual seeds or floating fragments of their roots. Once established, the new plants quickly enlarge into circular colonies that grow together, eventually coalescing and smothering out the diversity and much of the other life of the marshes.
  • And, if that wasn’t bad enough, add feral hogs into the picture.  They run rampant in the forest and wetlands of the Gulf Coast, but now, with the dense stands and mats of downed stems in each growth area of giant reed grass, the pigs have moved into the coastal marshes, living amongst the high and dry matted stems, hidden from hunters and from predators. The pigs are “bio-turbators,” meaning they dig up immense landscapes as they root around in the soils to find insects and tubers to eat. When they are done rooting around, the land looks like a disked-up surface, not unlike what remains after a farmer plows and dicks the soils.  These newly disturbed soils lay exposed and ready for any plant to re-colonize, including seeds of giant reed grass. The pigs thus contribute to the spread of giant reed grass.

Addressing the decline in the Gulf Coastal ecosystem will require an ecosystem restoration and watershed approach supported by policies and various incentives offered throughout the tributary watersheds. Any restoration approach must also recognize other threats including the rapid spread of invasive, non-native species. One example of an invasive threat is giant reed canary grass, which has the potential to dismantle entire ecosystems, if left unchecked. If recent years are any indication, hurricanes will continue to roar through the Gulf, making a dire situation even worse. Perhaps it’s best we consider the environmental ramifications during the hurricane off-season, before it’s too late.

[Image credit: Jessica Simpson, Flickr]

Steven Apfelbaum is the founder and principal ecologist at Applied Ecological Services (AES), a leading environmental conservation and restoration firm headquartered in Brodhead, Wisconsin. He is co-author of the Restoring Ecological Health to Your Landseries, which shows laypeople how to restore land to its natural state, and author ofNature’s Second Chance, a memoir recounting the thirty year restoration of his family’s dairy farmFor more information, visit www.appliedeco.com.


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