The Brown Pelican's Return to Coastal Louisiana - Part Two
A Vanishing Habitat
In brown pelican restoration efforts, the number of fledglings per nest is used by researchers to determine a given population's viability. Females usually lay two or three eggs per nesting, and research has shown that 1.2 to 1.5 young per breeding female are needed to ensure a stable, on-going population. Below 1.2 fledglings per nest, the population is invariably in decline; above 1.5, the population-barring catastrophic events such as hurricanes, epidemics, oil spills and the like-is likely on the increase.
In 1981, the year after the Florida to Louisiana transplant and nesting efforts ceased, the average number of pelicans fledged per nest on Queen Bess Island was nearly 1.4. The following year, that number had jumped to 1.8 per nest, a number that clearly indicated that the pelican population was expanding of its own accord. Over the next three years (1983-1985), the numbers showed remarkable stability, both in terms of the population itself and the annual fledgling numbers, with each year recording an average of 1.4 (± .02). The next five years (1986-1990), however, would tell an entirely different story, with the respective yearly averages of 1.25, 1.33, 1.20, 1.33 and 1.25 (a five-year average of 1.27) indicating that the Queen Bess colony was barely holding its own.
A good portion of the problem was that the barrier islands such as Queen Bess that the brown pelicans had been reintroduced to were facing their own "extinction" of sorts. Louisiana is struggling with a coastal land loss rate that is by far the worst in the nation. In addition to the 25-35 square miles of coastal wetlands that are lost each year to erosion and subsidence (i.e., lowering), barrier islands are also suffering at the hands of these same culprits. Across the past century, over 40% of Louisiana's barrier islands have sunk beneath the waters in the Gulf of Mexico. And those that haven't been lost have, on the whole, been drastically reduced in size. Queen Bess Island, for instance, is known to have deteriorated from its 45-acre extent in 1956 to 17 acres in 1989.
Although Louisiana's barrier islands are largely unpopulated by humans, the decline of the barrier islands was induced, for the most part, by human activities. As more people, industry and infrastructure moved into the bottom stretch of the Mississippi River Basin that runs from Baton Rouge through New Orleans and the port access afforded further to the south, the need to control the Mississippi's floodwaters increased. The modest embankments built at the turn of the 18th century evolved into the extensive levee system that girds the region today, and as construction technologies improved across the years, the Mississippi's flow has slowly but surely been tamed.
But from the point of view of the wetlands and barrier islands, the levee system has succeeded to a fault. For millennia, water would readily overtop the Mississippi's natural banks and flood vast expanses of what is now the south Louisiana coast. Carried in these waters were tons upon tons of sediment that the Mississippi had scoured from its banks on its 2,360-mile journey to the gulf. These sediments were absolutely crucial counterbalances to the natural forces of erosion and subsidence that wetlands and the outlying islands withstood. With the sediment delivery mechanism suspended, eroded areas could no longer cyclically reestablish themselves seaward as they had for eons. Moreover, because the loose, siltly deposits tended to compact over time, the viable lands were not only reduced in area but in height as well.
The barrier islands are also robbed of the sediments that once replenished them in another way. As with other wetlands, the so-called "bird's foot" delta at the Mississippi's very mouth has been experiencing extensive land loss as well, despite what might seem to be its opportune placement for sediment gains. The very existence of the Mississippi River Delta, in fact, is due to the sediment deposition that has historically occurred at the river's mouth. Yet once again, the extensively levied Mississippi proved to be the source of the delta's ills.
Like communities in Louisiana, flood-prone regions all along the river's length have built levees as well, and, much like plugging numerous leaks found along an old garden hose, the inevitable effect has been to increase the river's rate of flow. This has left the Mississippi coursing so fast that when it enters the gulf, the sediments it carries are no longer deposited on the surrounding shallows but instead travel some 50 miles out to sea where they settle into the depths beyond the continental shelf. With these deltaic sediments and those once suspended just past the delta's reach no longer available, the gulf's prevailing westward current can no longer carry them, as it once did, to shoal and accrete on the barrier islands.
Barrier Island Restoration
Enter the Breaux Act of 1990, also known as the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA). Because Louisiana contains 90% of the lower 48 states' intertidal coastal wetlands and accounts for 80% of the nation's intertidal wetland loss, the Breaux Act's primary focus was on the challenges facing coastal Louisiana. More than simply about habitat, the restoration effort is about safeguarding industry, infrastructure and lives. Nearly half of Louisiana's 2 million residents live in the state's 18 coastal parishes, a region that supports a $1 billion dollar a year commercial fishing industry, 20% of the nation's oil production, and a port complex that moves more tonnage per day than any other the world over. Barrier islands act as the first line of defense in protecting all of these industries against the destructive forces of hurricane winds and their associated tidal surges, with the intervening expanses of wetlands playing a similar protective role.
Several islands in Louisiana's barrier chain have been assigned CWWPRA projects in order to help preserve and restore them. One of these is Queen Bess Island, the very first to have fledged brown pelicans during the transplant efforts of the 1970's. In addition to losing 62% of its area from 1956 to 1989, Queen Bess Island was also rapidly sinking, with some portions of the island dropping over one foot during the 1980's. This reduction in size and height left Queen Bess vulnerable to storm tide overwash, the same set of events that affect other barrier islands by eroding (if not fully breaching them), destroying island vegetation, creating ponding areas, and sweeping nests and newly fledged birds out to sea. As a result of both habitat loss and the degradation of that which remained, Queen Bess lost roughly 66% of its hard won brown pelican population in the 1980's.
A picture of the Queen Bess project area taken immediately after construction.
Taken from the opposite side of the island, the image above clearly depicts the vegetative regrowth that serves as pelican habitat.
The Queen Bess Island CWPPRA project began in 1990. Consisting of two primary phases, Phase I centered upon building a shell retaining dike out in open water that approximated the island's original shell shoreline. With this retaining dike completed, over 150,000 cubic yards of material taken from the routine maintenance dredging of the Barataria Bay Waterway were placed between it and the existing island. In addition to this lateral expansion, several earthen dikes were created upon the remaining portion of the island, dikes that recreated and shored up the diminished natural ridges. These interior dikes were then planted with wax myrtle (Myrica cerifera), marsh elders (Iva frutescens), matrimony vine (Lycium halimfolia) and black mangrove (Avicennia germinans). Phase II of the project was the placement, in 1992, of 30,000 tons of rock protection around the entire island, completely armoring the island's newly established perimeter. The monitoring program that is standard to every CWPPRA program found that by the summer of 1992, the planted ridges were thriving, with one of the berms so completely covered with vegetation that it was impossible to distinguish the newly planted sections from those that had pre-existed.
Rock breakwaters, just after their installation, can be seen ringing Raccoon Island in the foreground.
In this later picture, sand deposits or "tombolos" can be seen developing behind the breakwaters. A similar effect is expected to occur behind the 8 additional breakwaters now being constructed to the west.
In 1987, a third nesting colony was created by the Louisiana Department of Wildlife and Fisheries on Raccoon Island, an island found south of the Terrebonne Basin in the Isles Deniers chain. As with Queen Bess and other barrier islands, Raccoon Island was rapidly losing ground and, along with it, valuable pelican habitat. Subsidence, a lack of sediment supply, storm overwash and the erosive force of wave energy combined to create a shoreline retreat of over 36 feet per year on the island's western end. In a 1997 CWPPRA "demonstration" project intended to test the utility of a brand new approach, eight detached, segmented breakwaters were placed as wave barriers south of the island's eastern portion.
While shoreline retreat remained a problem for the east end of the island because it still bore the brunt of the wave energy, waves were damped to the extent that the western shoreline has halted and perhaps even reversed its retreat. In addition, the breakwaters acted as sand traps, and sandbars have formed between the breakwaters and the island itself. In the wake of this success, CWPPRA has approved another project to help protect Raccoon Island. This time around, the breakwaters will be extended further to the west and several of the gaps between the existing breakwaters where the wave energy is most intense will be filled in with rock riprap. In addition, the bayside shoreline is set to receive sediment from a dedicated dredging program and, when sufficient height has been attained, vegetative plantings. When finished, the latter, deposition and planting aspect of this project alone is expected to provide some 60 acres of potential brown pelican habitat.
The Pelicans Take Off
As of fall 2002, Louisiana's brown pelican population seems to have been firmly stabilized. The organochlorine levels in their tissues and environment have continued to wane. Crucial nesting habitats have been shored up, and eight additional barrier islands have been naturally colonized by nesting brown pelicans. They are now seen as far north as Lake Pontchartrain, loafing and dive fishing some one hundred miles from their resident colonies. All told, those monitoring the birds now place the statewide count at roughly 50,000.
As for the immediate future, the aggressive monitoring program that the Louisiana Department of Wildlife and Fisheries has put in place indicates the true magnitude of the turnaround. Beyond the encouraging state total, the number of fledglings per nest continues to be one of the most critical indicators that the experts look to. In 2002, that number for Queen Bess Island alone was at 2.3, a vast improvement over the 1.27 average that was the cause for concern in the late 1980's. Raccoon Island's number, too, at 2.0, indicates a thriving, expanding population. In fact, the ten islands upon which the brown pelicans now nest have a fledglings per nest average of 2.1, with none of the individual islands having a fledgling rate less than a 2.0. And although this number represents an unusually successful nesting season, over the last ten years, the fledgling to nest ratio has been a robust 1.7.
Given their complete extirpation from Louisiana in the 1960's, the fact that not a single brown pelican was fledged again in the state until the 1970's, and the habitat challenges the species has faced over the last two decades, the current brown pelican population and the nesting success of the last several seasons are truly remarkable. Just as the brown pelican's sudden disappearance from Louisiana's shores in the 1960's was a signal event in American ornithology, their successful reintroduction and return to historical population numbers has to be considered one of the greatest success stories in the history of U.S. wildlife ecology. No longer found only on Louisiana's flag, her state seal or in a handful of struggling, closely watched colonies, the brown pelican has returned to its rightful place in the state. And whether they are found soaring on gulf breezes, caring for their hatchlings on the ground, or diving beneath the waters for a meal, they seem perfectly happy to be back home.