For millennia, the Mighty Mississippi deposited countless tons of fertile sediment where the river meets the Gulf, creating a vast, productive marsh once covering some 3 million acres. Today, fewer than 2 million acres are left, and these remaining marshes are not considered adequate to support waterfowl populations at desired management levels. Nevertheless, extensive high-quality waterfowl habitat remains, especially in shallow intermediate- salinity and freshwater ponds scattered throughout the marsh. These ponds, under appropriate growing conditions, support dense beds of submersed aquatic plants, including various species of pond weed, southern naiads, and many others—offering in effect a salad bar for ducks.
These plants also provide habitat for a host of aquatic insects and crustaceans, rich sources of protein ducks need to complete their winter molt and prepare for spring migration. Moreover, beds of submersed vegetation serve as nursery habitat for a variety of commercially important fisheries, including white and brown shrimp and blue crabs. Submersed aquatic plants are a key part of the foundation that supports the region's enormous biological productivity.
Photo: Dale Humburg, DU
But uncertainties remain about how the oil spill will affect scaup, redheads, and other waterfowl that largely use offshore habitats. Deeper brackish bays and lakes, such as Lake Pontchartrain and Lake Borgne, regularly winter approximately 500,000 lesser scaup. In addition, large numbers of scaup—in some years more than 1 million birds—winter in the Gulf off the southeast Louisiana coast. To the east, sizeable concentrations of scaup occur in Mississippi Sound, Mobile Bay, Tampa Bay, and Charlotte Harbor—all areas that were vulnerable but appear to have mostly been spared from oil impacts. Questions remain, however, regarding how the oil spill will affect small marine clams, believed to be the staple food of wintering scaup. If the abundance of clams declines significantly in oil-impacted waters, scaup may be forced to migrate to other areas—certainly not ideal, but something the birds are well adapted to do. In a more troubling possibility, filter-feeding clams could absorb toxins derived from oil or chemical dispersants. If consumed in large enough quantities (by scaup feeding on clams) these toxins could directly kill or weaken birds or cause reproductive problems for breeding females in the future. Given that scaup numbers are already at depressed levels, any large-scale impacts to the population would be devastating.
In contrast, redhead numbers are currently healthy and more than 85 percent of the population winters in the Laguna Madre of Texas and Mexico, far to the west of the area currently impacted by the oil spill. But about 10,000 redheads winter near the Chandeleur Islands just off the southeast Louisiana coast, which have already been heavily impacted by oil. Another 80,000 redheads winter in the Big Bend of the Florida Gulf Coast from Panama City to Cedar Key—an area that appears to have been spared from most oil impacts. Redheads feed largely on shoalgrass and other submersed aquatic plants. If this vegetation is killed or contaminated by oil, redheads wintering in these areas would be subject to the same biological threats as scaup. Uncertainty abounds, but the U.S. Fish and Wildlife Service, with input from Ducks Unlimited and others, is working to assess potential oil-spill impacts on scaup, redheads, and other waterfowl.
|Regardless of whether the oil spill worsens ongoing habitat losses, the need for long-term conservation strategies to sustain the region's wetlands and waterfowl populations has never been more urgent.
While the Gulf oil spill is an almost incomprehensible environmental catastrophe, this region's fragile coastal wetlands were already in grave danger before this disaster unfolded. Louisiana has already lost more than 1.2 million acres of its most productive coastal marsh. In addition, rice agriculture in south Texas and Louisiana, which provides important foraging habitat for wintering ducks and geese, has declined by roughly 50 percent in recent decades. Regardless of whether the oil spill worsens ongoing habitat losses, the need for long-term conservation strategies to sustain the region's wetlands and waterfowl populations has never been more urgent.
In March, Ducks Unlimited completed a 10-year strategic plan outlining the direct programs, public policy, and scientific research needed to advance our conservation goals in the Gulf Coast region. In cooperation with a host of conservation partners and with support from DU members across North America, we must increase our efforts to restore and sustain coastal wetlands for waterfowl and all who value them as part of our waterfowling heritage. DU was working hard to restore Gulf Coast wetlands prior to the oil spill, and we will remain there as long as it takes to ensure these vital habitats—and the region—can support healthy waterfowl populations today and in the future.
For the latest news and analysis about the impacts of the Gulf oil spill on wetlands and waterfowl, visit the DU website at www.ducks.org.
Dr. Tom Moorman is director of conservation planning in DU's southern region and leader of DU's Gulf Coast Response Team.