Barataria-Terrebonne Estuary
The Barataria-Terrebonne Estuary, located in southeastern Louisiana between the Atchafalaya and Mississippi Rivers, encompasses over four million acres of vital estuarine and wetland habitats. This region is part of one of the world’s largest river deltas and is characterized by a rich mosaic of ecosystems, including salt marshes, brackish and freshwater marshes, and cypress-tupelo swamps. These habitats support a diverse array of wildlife, hosting nearly 700 species of animals, including numerous birds, fish, and invertebrates, while also playing a critical role in the livelihoods of local human communities. The estuary is particularly important for commercial fishing, making Louisiana a leading seafood producer in the United States, and serves as a recreational resource for residents and visitors alike.
However, the Barataria-Terrebonne Estuary faces significant challenges, including one of the highest rates of wetland loss globally. Since the 1930s, the region has lost approximately 25% of its land area, primarily due to the isolation of the Mississippi River from the surrounding wetlands and the impacts of oil and gas industries. Additionally, factors such as climate change, invasive species, and the aftermath of events like the BP Deepwater Horizon oil spill continue to threaten its ecological integrity. The future of the estuary hangs in the balance, with projections indicating the potential loss of over 4,000 square miles of land in the coming decades if proactive measures are not taken.
Barataria-Terrebonne Estuary
- Category: Marine and Oceanic Biomes.
- Geographic Location: North America.
- Summary: This estuarine and wetlands habitat on the northern edge of the Gulf of Mexico supports wildlife and human populations—but is rapidly disappearing.
Deep in southeast Louisiana, between the Atchafalaya and Mississippi Rivers, lies more than four million acres (two million hectares) of estuarine and associated wetland habitat. The Barataria-Terrebonne Estuary, part of one of the largest river deltas in the world, supports diverse wildlife and a vibrant human culture that depends on its habitats for food, shelter, jobs, and recreation. The wildlife and human communities are threatened, however, by one of the highest rates of wetland loss in the world.
Barataria-Terrebonne is a mosaic of habitats shaped largely by a transition from saltwater to freshwater that extends more than 25 miles (40 kilometers) inland. Thick seagrass beds grow in the shallow waters of the northernmost part of the Gulf of Mexico. Salt marsh, a habitat dominated by smooth cordgrass (Spartina alterniflora), fringes the coast. As salinity decreases inland, brackish and then intermediate marsh grows. Farthest away from the sea, and most influenced by rainfall and river water, is freshwater marsh.
By one estimate, the diversity of plants in the freshwater marsh here is five times higher than that in the salt marsh. There are also shrubby and forested habitats within and between the broad swaths of the marsh. Bottomland hardwood is a type of forested wetland along the rivers' edges, while cypress-tupelo swamp is a nearly perpetually flooded habitat dominated by iconic bald cypress trees (Taxodium distichum).
Animal Biodiversity
The coastal habitats of Barataria-Terrebonne are critical to both land-dwelling and marine animals. Nearly seven hundred species of mammals, birds, reptiles, amphibians, and fish live in the Barataria-Terrebonne part or all of the year, along with a vast array of invertebrates like shrimp and oysters. The wetlands are winter habitat for waterfowl and raptors from Canada and the northern United States, and nesting habitat for colonial birds like brown pelican (Pelecanus occidentalis). Over 400 species of birds are known to occur in the estuary. Seventeen species of wading birds dwell in the area, including the tricolor heron (Egretta tricolor).
Larval fish and shellfish use the wetlands as nursery habitats, feeding in warm, shallow waters and hiding from larger predators. For migratory songbirds moving from Latin America to Canada's boreal forest, Barataria-Terrebonne's coast is an important resting spot after a grueling flight over the gulf. These lush resources inspired early French settlers to give Terrebonne Parish, the southwest corner of Barataria-Terrebonne, its name: Terre Bonne means “good earth.”
Today, the resources of Barataria-Terrebonne still shape the lives of the people who live there. The region is the most densely populated part of Louisiana's coastal zone outside of New Orleans. One of the most important occupations in Barataria-Terrebonne is commercial fishing, and fish landings in this region help make Louisiana the second-largest seafood producer in the United States. Hunting and recreational fishing are important pastimes for residents and visitors and lucrative sources of income for the tourist industry. Wetland vegetation also provides coastal protection, reducing shoreline erosion and the destructive power of hurricane-driven waves and storm surges.
Wetland Loss
For nearly 80 years, Barataria-Terrebonne's rich landscape has suffered a slow-motion collapse that has inundated wetlands and human communities alike. Coastal Louisiana lost nearly 1,892 square miles (4,900 square kilometers) of land between 1932 and 2010, or about 25 percent of the land area present in 1932. About half that loss occurred in Barataria-Terrebonne. One of the main causes of the wetland loss is the isolation of the Mississippi River from the surrounding wetlands.
The Mississippi River drains a watershed covering 41 percent of the continental United States. Over much of the past 10,000 years, sediments from the river dropped into shallow gulf waters and built land seaward in a series of overlapping delta lobes. Every 1,000 to 1,500 years, the river changed course, building land in a new lobe adjacent to the river and abandoning the old lobe. Barataria-Terrebonne is made of three such lobes, the oldest of which started to form about 5,500 years ago. The elevation stayed above sea level as long as new land was built at the same rate as the old land subsided. When the lobes were abandoned, subsidence and marine processes began to dominate, and the extremely productive Barataria-Terrebonne Estuary biome evolved.
As of 2024, the wetlands were still subsiding. According to the state of Louisiana, if no action is taken, more than 4,000 square miles (6,437 square kilometers) of land could be lost in the next fifty years.
Other Ecosystem Threats
The wetlands are subject to many other challenges. The oil and gas industry has cut more than 9,942 miles (16,000 kilometers) of canals through the marsh, allowing saltwater to flow into normally fresh areas. When canals are dredged, the spoil or sediment is usually deposited along the banks, which blocks natural tidal inflow to the marsh surface beyond. This reduces new sediment from spreading across marshland, which often results in the reversion of the habitat to open water. Large withdrawals of oil and gas from Barataria-Terrebonne have also sped subsidence.
Tropical storms and hurricanes are double-edged swords: Although they can nourish some wetlands by depositing sediment, they can devastate others, ripping up vegetation and pushing saltwater far inland.
Invasive species can disrupt waterflow, destroy habitats, and reduce native populations as they compete for the same resources. Dozens of exotic plants have already been introduced and become established at Barataria-Terrebonne. These plants can block navigation and impede water flow. Exotic animals create an additional threat. Nutria (Myocastor coypus), large rodents introduced to Louisiana in the 1930s, can rapidly turn wetlands into open water through their ravenous feeding upon plant stems, roots, and rhizomes, along with their widespread compacting of vegetation to build burrows and dikes, much in the manner of beavers.
The BP Deepwater Horizon, an oil rig 50 miles (80 kilometers) off Louisiana's shores, exploded in 2010, spilling up to 185 million gallons (700 million liters) of petroleum into the gulf. It will be years before scientists know the full impact of the BP oil disaster on Barataria-Terrebonne. Finally, Barataria-Terrebonne's low-lying coast is vulnerable to the effects of global warming—particularly changes in rainfall patterns and global sea-level rise.
Bibliography
Couvillion, Brady, et al. Land Area Change in Coastal Louisiana From 1932 to 2010. U.S. Geological Survey, 2011.
Hemmerling, Scott. "Barataria-Terrebonne Estuary System Climate Change Adaptation Plan 2020." The Water Institute of the Gulf, 2020, thewaterinstitute.org/projects/barataria-terrebonne-estuary-system-climate-change-adaptation-plan-2020. Accessed 30 Oct. 2024.
Naquin, Brandon. "Canals, Community, and Coastal Permits: Overcoming Inadequate Remedies for Erosion within the Barataria-Terrebonne National Estuary." Emory Law Journal, vol. 70, no. 3, Jan. 2021, pp. 663-710. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=149062518&site=ehost-live. Accessed 30 Oct. 2024.
National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. "Deep Water: The Gulf Oil Disaster and the Future of Offshore Drilling—Report to the President." Government Publishing Office, Jan. 2011, www.gpo.gov/fdsys/search/pagedetails.action?packageId=GPO-OILCOMMISSION. Accessed 30 Oct. 2024.