Status of Biological and Physical Resources - Coastal Erosion - Marsh Restoration/Reclamation
Wildlife and Fisheries Resources
Because of its unique location, Rockefeller Wildlife Refuge is one of the most important wildlife areas in the United States. Louisiana’s position at the southern terminus of the Mississippi and Central Flyways allows the state to serve as a wintering home for waterfowl from northern nesting grounds. RWR hosts hundreds of thousands of ducks, geese, coots, and numerous shorebirds/wading birds each year with 273 species documented on the refuge (Appendix 2). This includes providing wintering habitat for the federally Threatened Piping Plover (Charadrius melodus). The refuge and surrounding chenier “ridges” also serve as critical spring stop-over habitat for many neotropical migratory birds on their journeys to northern breeding grounds, while also serving as a “last stop to fuel” on their fall journeys to Central and South America. Further, the refuge serves as a very important fisheries nursery (including crustaceans) for the southwestern Louisiana coast, and RWR has played a pivotal role in the recovery of the American alligator and its habitat.
Timber or Botanical Resources
Since almost all of the 72,650 acres of RWR encompasses coastal marshes, there is little property that maintains any valuable timber resource. The only trees on the property are located near the headquarters along the chenier and along marsh levees, with primary species including live oak (Quercus virginiana), “hackberry” (Celtis laevigata [sugarberry]), and tallow tree (Triadica sebifera). No current or future forest management plans are anticipated, except possible management of the invasive tallow tree. RWR staff is in the planning stages of a Chenier Restoration Initiative for Cameron and Vermillion parishes due to the ability for the cheniers to mitigate storm surges/damages and for their important wildlife values.
While RWR contains live oaks (Quercus virginiana) and hackberry trees (Celtis laevigata) on the most northern portion of the property along the chenier ridge, the refuge is primarily comprised of four distinct vegetative coastal marsh zones. The salt content of the surface water and the soil properties play a large role in the type of vegetation seen throughout the marsh. The site is comprised of fresh, intermediate, brackish, and salt marshes (Chabreck and Linscombe 1997).
Mammals.—There are no federally Threatened/Endangered mammal species that occur on the refuge. It is possible that the federally Endangered finback (Balaenoptera physalus), Sei (Balaenoptera borealis), blue (Balaenoptera musculus), and sperm (Physeter macrocephalus) whales occur within the Gulf of Mexico waters bordering the refuge. Other than previous research of furbearers on the refuge (i.e., nutria, muskrat, otter), little is known about the non-game mammal species on the refuge. A comprehensive survey for bats and small mammals on RWR would be a valuable research project to undertake by Rockefeller staff biologists.
Birds.—Only one federally Threatened bird species, the Piping Plover (Charadrius melodus), occurs on Rockefeller Wildlife Refuge. Piping Plovers overwinter on the beaches and mudflats of the Gulf of Mexico, including the 26 miles of undisturbed beaches of RWR. The only refuge management practice that benefits Piping Plovers is that RWR beaches are off-limits to public access, which is only possible by gated levee road via Price Lake Road. This practice decreases human disturbance, as well as habitat destruction by motorized vehicles. The number of Piping Plovers that currently utilize RWR beaches during the winter is unknown, but recent preliminary shorebird surveys noted three individuals immediately west of the Price Lake Road beach access levee (W. Selman, pers. obs.).
In addition to Piping Plovers, 48 birds that are Louisiana Species of Special Concern (SSC) have been observed on RWR. Many of these species are shorebirds which inhabit similar environs as the Piping Plover, and therefore, management practices also benefit these species. Other bird SSC that inhabit RWR include several wading birds and five waterfowl species (Canvasback, Lesser Scaup, Mottled Duck, Northern Pintail, Redhead). Most of the management activities within the units managed benefit both waterfowl and wading bird species.
Reptiles and Amphibians.—No federally Threatened/Endangered reptile or amphibian species occurs on RWR, but five federally Threatened/Endangered sea turtle species occur in waters of the Gulf of Mexico (Leatherback Sea turtle [Dermochelys coriacea, E], Loggerhead Sea turtle [Caretta caretta, T], Green Sea turtle [Chelonia mydas, E], Atlantic Hawksbill Sea turtle [Eretmochelys imbricata, E], and Kemp’s Ridley Sea turtle [Lepidochelys kempii, E]). The only sea turtle species that may use RWR beaches for nesting is the Loggerhead Sea turtle, which has been noted to nest in the eastern part of the state (Breton and Chandeleur Islands); this, however, is an improbable occurrence. Both Loggerhead and Kemp’s Ridley carcasses are occasionally found on Rockefeller beaches (W. Selman, pers. obs.).
Outside of alligator documentation, little is known on the distribution of other herpetofaunal species on RWR besides incidental encounters. Louisiana Species of Special Concern that may occur on the refuge/nearby cheniers include the Diamondback Terrapin (Malaclemys terrapin) and the Slender Glass Lizard (Ophisaurus attenuatus).
The former is found in saline/brackish marshes and tidal creeks, while the latter is considered “more abundant on the coastal cheniers of Cameron Parish than in any other part of Louisiana” (Dundee and Rossman 1989). A systematic survey of the herpetofauna of RWR and the surrounding coastal cheniers is needed.
Freshwater/Marine Fish.—No federally Threatened/Endangered freshwater or marine fish species are known to occur on RWR. Three SSC have been documented on RWR, including the violet goby (Gobioides broussoneti), gulf pipefish (Syngnathus scovelli), and largescale spinycheek sleeper (Eleotris amblyopsis), with many other species likely occurring within the brackish/saline marshes of RWR. A comprehensive study of the fish assemblage of RWR would be a worthwhile project for Rockefeller staff biologists to undertake since the last comprehensive survey completed was by Perry et al. (1965).
Exotic, Invasive, and Nuisance Species
The impact of exotic, invasive, and nuisance species is estimated to be one of the leading causes of species decline in the United States (Czech et al. 2000). The invasive species that occur on RWR are primarily Chinese tallow tree (Triadica sebifera), water hyacinth (Eichornia crassipes), Salvinia sp., roseau cane (Phragmites australis), and nutria (Myocaster coypus). Chinese tallow trees primarily occur along the chenier ridge and levees within the marsh, but there is no current plan to control/eradicate the species on RWR. Infestations of water hyacinth and Salvinia species were common prior to the hurricanes during 2005 (Rita) and 2008 (Ike). These hurricanes brought high levels of salinity to freshwater marshes and effectively eradicated any infestations on the refuge. In the future, it is likely that these species will return and be a problem to the refuge via the freshwater waterways to the north; the outbreaks can be controlled by saltwater introductions into units without compromising the isohaline line in Grand Lake. Infestations of roseau cane have increased within the Price Lake unit and herbicidal applications may be needed in future management of this species. Nutria is considered an exotic species from South America, but it has become naturalized in Louisiana; it was originally introduced into the marshes of Louisiana in 1930s for its then valuable pelt for the fur industry. The presence of this species on the refuge is minimal following the saltwater inundation of the refuge by hurricanes Rita and Ike.
The canals dug by early oil exploration in coastal Louisiana (including on RWR) have had lasting impacts on the surrounding landscape; canals allow for the rapid movements of water across the marsh, as well as easier routes for saline encroachment on freshwater marshes. However, RWR is an excellent example of how conscientious mineral development can be compatible with wildlife management. Negative environmental impacts of drilling have been minimized due to a cooperative relationship between wildlife managers and mineral production companies. The importance of the revenues generated from mineral leases on RWR cannot be overstated; they are used for wildlife research, habitat management/enhancement, to purchase/repair refuge equipment, land acquisitions, and salaries. Therefore, the responsible production of new wells is encouraged due to the lasting benefits the revenues will have for conservation on the refuge.
The original discovery of oil/gas within RWR occurred in 1952, with four oil/gas fields being developed since then. Fields that were developed include: Deep Lake (discovered 1952), Little Pecan Lake (1952), Constance Bayou (1953; no longer active), and Price Lake (1962; no longer active), with the Deep Lake Field being the most productive of the four (1.2 trillion ft3 of natural gas were produced between 1952 and 1989). Cumulative peak oil/gas revenues (all fields) for RWR approached 1.2 million dollars per month (14.4 million dollars per year) in 1984. Oil/gas revenues have decreased significantly since 1984 to approximately 2.8 million dollars in the 2008-2009 fiscal year. As of 2009, there were 11 active leases on the refuge that totaled 7,573 acres (~9% of refuge; Fig. 4) and six were under production. Active leases primarily occur in the vicinity of the East End Locks (Units 1, 3, 4), Superior-Deep Lake (Units 5, 6, 8, 10/13), and in the marsh to the southwest of Pecan Island (Unit 15, unmanaged eastern marsh).
Cultural or Archaeological Resources
To the best of our knowledge, no cultural or archeological resources occur on RWR. Interestingly, in 1766, the Spanish ship El Nuevo Constante shipwrecked off of RWR shoreline while carrying supplies and valuables back to Spain. The shipwreck occurred approximately 1,600 feet from the historical shoreline near Big Constance Bayou and a campsite was completed onshore approximately 2 miles from the wreck. However, shoreline erosion of approximately 5,000 feet has occurred in the interim time period, and therefore, it is unclear if the El Nuevo Constante campsite remains. If so, it could occur on RWR.
Hurricanes Rita/Ike and their associated storm surge dramatically reshaped the landscape of southwestern Louisiana and the primary facilities of Rockefeller Wildlife Refuge. Most of the buildings on the refuge have recently been repaired/replaced, are currently being repaired, or are planned to be replaced/repaired.
Restoration Techniques and Mitigation
As previously mentioned, RWR is losing ~ 28.5 ft. per year of coastal wetlands due to coastal erosion (Byrnes et al. 1995). RWR has worked extensively with visiting groups to showcase and discuss the extent of coastal erosion on the refuge. The refuge was also selected for a Coastal Impact Assessment Program (CIAP) project to evaluate different test scenarios for shoreline stabilization. These test scenarios will be evaluated and are planned to be expanded into a larger Coastal Wetland Protection and Restoration Act (CWPRA) project which will extend along the western 9-10 miles of RWR shoreline.
RWR has actively worked to reestablish marsh vegetation in “ponded” areas of the refuge, including within Price Lake and Units 4, 5 via terracing; this improves waterfowl habitat and stabilizes the marsh by reducing wave action. Marsh grasses (primarily Spartina alterniflora) have been planted along the canals within RWR to reduce wave action and associated levee erosion. Further, “marsh creation” mitigation projects have been completed (and are planned) to use dredge spoil to positively impact marsh health. In marshes that have subsided and/or been degraded to open-water conditions, dredge spoil is pumped into marshes in order to bring elevations back to “marsh level.” The areas targeted for marsh creation projects include a 4.7 acre site (completed), a 66 acre site near Deep Lake (near completion), and a 100 acre site south of the East End Locks (planned). Other avenues for marsh creation that may be considered in the future would be reclaiming abandoned oil field canals; this would reduce the ability for water to quickly move across the landscape, while also reducing levee mileage and concurrently the amount of maintenance needed on levees. Lastly, RWR has worked with CWPRA to establish a freshwater introduction project, primarily using additional water control structures, on the eastern part of the refuge in order to restore more natural flow conditions south of Hwy 82.
The greatest single threat to the refuge is the persistent problem of coastal erosion. Due to the receded shorelines and lost of vegetative marshes, the refuge has lost over 14,000 acres since it was deeded to the state in 1914 (~150 acres per year). RWR has an imminent need to develop techniques and secure funding to implement projects to lessen this state-wide concern. Recently, RWR was fortunate to be selected for a CIAP project to evaluate different test scenarios for shoreline stabilization. Sponsored by Department of Natural Resources, the $9.3 million project began in June 2009 with construction of a low profile reef breakwater section. This was followed by placement of a section of beach fill constructed of crushed stone and the last test was a rock reef breakwater placed on a lightweight aggregate core.