The State of the Gulf of Mexico
As the ninth-largest body of water in the world, the gulf is amazingly resilient — but how much more can it take?
By Larry McKinney
The Gulf of Mexico, at more than 579,000 square miles, is the ninth-largest body of water in the world. It is bounded by Texas, Louisiana, Mississippi, Alabama and Florida on the north; six states of Mexico on the west and south; and Cuba on the east. It is one of 10 large marine ecosystems adjoining the continental United States and probably the most easily recognized on a map. As an ecosystem, the gulf functions on a scale that even a Texan might appreciate.
Yet every day, you and I (and millions like us throughout the gulf states and much of the heartland of the country) affect the health of this ecosystem in practically everything we do — cooking, cleaning, watering the lawn, flushing the toilet and even driving the car. When amplified by the millions of us who live on the watersheds that empty into the gulf, there is clear evidence that we are determining its future — and our own.
The gulf is a giant bowl whose wide margins are dominated by shallow bays, estuaries and coralline shelves as well as a relatively extensive continental shelf and slope. The gulf is primarily sedimentary in origin, with vast expanses of undulating soft mud bottoms, especially to the north. Emergent features like the Flower Garden Banks, the northernmost coral reefs in North America, punctuate these bottoms throughout the gulf and transition into carbonate banks and coral reefs to the south. These physical features define the framework for a unique ecosystem often referred to as the "American Mediterranean."
All of these factors combine to support one of the most productive bodies of water in the world. Commercial fisheries annually yield more than 1.5 billon pounds. Shrimp are the predominant species and can account for 68 percent of total U.S. landings. Oyster production can exceed 24 million pounds and account for 70 percent of U.S. total landings. Recreational fishing is a significant economic engine. More than 45 percent of all saltwater anglers fish in gulf waters. Texas and Florida dominate all statistical categories of saltwater fishing, and each year anglers generate billions of dollars in economic benefits for their states. Louisiana's license plate proudly proclaims the state as a "sportsman's paradise," and if you have ever been there you can see why. A great part of the gulf's amazing productivity comes from the seemingly endless miles of Louisiana wetlands. While not as massive as Louisiana's, the estuaries and wetlands of Mississippi, Alabama, Texas and Florida are also brimming with life. As a result, the Gulf of Mexico annually yields more finfish, shrimp and shellfish than the south- and mid-Atlantic, Chesapeake and New England areas combined. It might surprise a Yankee sitting down to crabcakes or oysters on the shores of the Chesapeake that their meal actually came from the gulf, but more often than not, that is the case.
Like a string of pearls, gulf estuaries dot the margins of the northern gulf and are the engines that drive the region's incredible productivity. An estuary is where the sea and a river meet — where sediment- and nutrient-laden freshwater mixes with seawater. This dynamic mixing produces a rich, often brown and turgid-looking soup that fuels the nursery habitats upon which 90 percent of all the commercially and recreationally important fish and shellfish of the gulf depend. The 39 major gulf estuaries account for nearly 42 percent of such areas in the United States, so it should be no surprise that the gulf is as productive as it is.
The Gulf of Mexico is not only productive, it is also diverse. Because of its location, it is transitional between temperate and tropical climates and includes elements of both. It is a major transit route for migratory songbirds moving between the Americas each season and the southern terminus of North America's central flyway for migratory waterfowl, seabirds and wading birds that annually winter around the gulf — about 75 percent of all those traversing the U.S. From whooping cranes to hummingbirds, the diversity and abundance of birdlife is unequaled elsewhere in the subtropical world. More than 400 species of shelled mollusks can be found along the extensive beaches of the gulf, more than can be found on any other U.S. shore. Some 200 kinds of reef fishes can be found on the Flower Gardens, one of the most pristine reefs in the world. The benthic communities of the northern mud and sand bottoms are among the best developed and most diverse anywhere, and the coral reefs of the south and east host a diverse and complex community.
The underpinning for this extraordinary productivity and biodiversity is an extensive complex of ecologically diverse habitats. The primary habitat of the northern estuaries is emergent wetlands — vast swaths of waving saltgrass. Coastal wetlands in the gulf exceed 5 million acres and account for about half the U.S. mainland total. Adjacent uplands and coastal watersheds play a key role in the health of these wetlands. The estuarine mud and sand bottoms are dominated by extensive benthic communities interrupted by numerous oyster reefs. In the shallow offshore marine waters, similar mud and sand bottoms are dotted by hard banks in the north and coral reefs in the south, contributing significantly to the biodiversity of the region. Well-known systems like the Laguna Madre of Texas and Florida Bay host extensive seagrass meadows and mangroves. These and other southern bays of Florida and Mexico transition into coral reefs as one moves south.
The Gulf of Mexico faces increasing challenges to its overall health. The gulf's future productivity and biodiversity are inextricably linked to the vitality of the ecosystem. All of the countries surrounding the gulf are experiencing a rapidly expanding population and accompanying economic development. A 40 percent increase in population (reaching 61.4 million) is expected by 2025. Oil and gas production in both nearshore and deeper waters of the gulf continues to expand, as do port facilities, the petrochemical industry and other businesses necessary to support the economic needs of the region. The loss of habitat to coastal development in response to a growing population, the diversion of freshwater inflows from estuaries to meet the demands of that growth, and diminished water quality due to wastewater discharges add up to a high degree of stress for even the "large marine ecosystem" called the Gulf of Mexico.
An ecosystem can be defined as the dynamic interaction of a community of organisms (including us in the case of the gulf) and their environment. One of the primary drivers of these interactions in the gulf is the Mississippi River. One of the world's great rivers, it drains some 41 percent of the continental U.S., 31 states and two Canadian provinces, about 1.8 million square miles. At a discharge rate of 600,000 cubic feet per second near New Orleans, the river accounts for nearly 90 percent of the freshwater discharge into the gulf. That flow moves as much as 159 million tons of sediment a year down the river and with that sediment all the nutrients and wastes that are not captured and treated along the way.
Like a huge hypodermic needle, the Mississippi injects this watery mix into the heart of the gulf and creates a "dead zone" that expands from the mouth of the river each year. The zone is caused by algae blooms, which the nutrient-rich waters encourage. The algae die and sink to the bottom, where decomposition by oxygen-consuming bacteria depletes surrounding water of most or all of its oxygen, creating hypoxic conditions in which few marine organisms can live. The size of the zone varies annually and in 2007 reached 7,900 square miles, about the size of Connecticut and Delaware combined. The creation of the dead zone has been attributed to fertilizer runoff from as far away as the Corn Belt. Ironically, the push to increase corn-based ethanol production, a response to climate change, could greatly expand the extent of the dead zone. That expansion, if it were to occur, would likely aim right at Texas and some of our most productive coastal waters.
Some indicators of stress are easier to see than hypoxic dead zones because we drive through them every day. As coastal populations grow, wetlands are filled to meet housing and transportation demands. Bay bottoms are channelized and access areas near ports are dredged deeper. Freshwater is diverted and flood control levees and canals are constructed. As a result, coastal erosion is a significant problem. Each year, 40 to 60 square miles of Louisiana wetlands disappear. Some 60 percent of Texas' shoreline is eroding and the state has lost almost half its original coastal wetlands. In Florida more than 20,000 acres of mangroves have disappeared. The Everglades and even the wetlands of the mighty Mississippi are threatened because of the diversion of freshwater to agricultural and municipal needs or for flood control.
Perhaps nothing has brought home the implications of these environmental insults more than the aftermath of the horrific hurricane season of 2005 (a record 15 hurricanes) and especially Katrina and Rita. Hurricanes are natural phenomena integrated into the functioning of a healthy gulf ecosystem. Shallow coastal habitats have evolved to absorb the high energy impacts generated by these storms and equilibrium can quickly return to the system. Manmade alterations to and destruction of wetlands and natural infrastructure like oyster and coral reefs have diminished even this large marine ecosystem's resilience and its ability to return to those levels of ecosystem health and productivity that might otherwise be anticipated. The hurricanes vividly illustrated what the loss of healthy coastal wetlands means to moderating erosion and storm surge. They also brought into focus water quality concerns related to the diversion and manipulation of freshwater re-sources in these areas. One reason the storms were so devastating was the lack of natural wetland barriers that would have otherwise buffered the impacts of the storms. It is estimated that for every four miles of wetlands, storm surge is reduced by a foot. In the flat coastal plains that surround the gulf, any reduction in storm surge represents a significant reduction in damage and even loss of life. What one sows one also reaps. One of the hard lessons learned from those hurricanes was that coastal wetlands are not just for the birds and fish — we need them as well.
The hurricanes and dead zones of recent years should be a wakeup call for all of us. The Gulf of Mexico is dynamic and productive and has been able to absorb all that has been thrown at it, so far. The question is: How much more? That is a question we must not ignore and one we do not want to answer through experience. Fortunately, many organizations have long recognized the challenges we face and have been working diligently and often with little recognition to address these problems.
One such group is relatively new but holds the promise of bringing a constructive focus to this important issue. The Gulf of Mexico Alliance is a partnership, established in 2004, of the states of Alabama, Florida, Louisiana, Mississippi and Texas with the support and leadership of each state's governor. The alliance was formed in response to a report from the U.S. Commission on Ocean Policy, "An Ocean Blueprint for the 21st Century," and President Bush's response to it — the U.S. Ocean Action Plan. The alliance is bringing together local, state and federal agencies, as well as nongovernmental organizations, academics and concerned individuals, to assure that the gulf we enjoy and benefit from so much today will exist for tomorrow.
The encouraging aspect of this effort is that it is driven by the states but with great support from federal agencies like the Environmental Protection Agency and the National Oceanic and Atmospheric Agency, to name just two. While the alliance is touted as a national model, time will tell if it can meet its promise. All of the elements are in the mix, and the key will be the political will to move it forward. That is where we all can help by encouraging our political leadership to support the effort.
We cannot hope to be successful in managing this magnificent resource unless we have a sound science base on which to make those decisions that will affect the future of the gulf. Another relatively new player has stepped up to help with that: the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University - Corpus Christi. In the spring of 2006 the institute held the first of several planned summits to bring together scientists and policymakers.
Finally, all of us by our individual actions can together make a difference. The old saying that all rivers lead to the sea is a true one, and all that is dumped into them makes that same journey. Rethinking how we take care of our lawns to reduce fertilizer and water use, protecting the creeks and streams that run through our neighborhoods, and recognizing that we are each part of that large marine ecosystem called the Gulf of Mexico will make all the difference for it and for us.