Prospects for Key Waterfowl Regions
DU believes that the prospects of climate change are serious, and we are taking steps to keep informed and do prudent contingency planning for conservation. There remains, however, a great deal of uncertainty about how this global drama will play out, and that too must be considered as we plan for the future. Here's a sampling of projections for some of DU's high priority conservation regions:
Prairie Pothole Region
The Prairie Pothole Region is the single most important breeding area for waterbirds in North America. Average spring temperatures have increased in this region over the past 50 years, and all global climate models predict further warming.
Expected ecological changes include fewer wetlands on average; shorter flooding duration for wetlands; greater annual variability in surface water; changes in agriculture; and changes to water depth, salinity, temperature, plants, and aquatic food webs.
Drought affects the breeding success of prairie ducks by decreasing the likelihood of breeding at all; and by causing reduced clutch sizes, shorter nesting seasons, reduced likelihood of renesting, lower nesting success, and lower brood survival, collectively resulting in fewer ducks being produced.
Some low-risk adaptations to these threats might include:
1) targeting long-term waterfowl conservation actions to less vulnerable subregions of the prairies
2 )protecting native parkland habitats at the northern fringe of the pothole region where longer growing seasons will favor agricultural expansion
3) reducing existing human-caused stresses on wetlands (e.g., drainage, filling, road impacts) and associated uplands (e.g., overgrazing, intensive tillage)
4) restoring or protecting complexes of wetlands in order to hedge against variable moisture conditions
5) contingency planning for large managed wetlands (e.g., securement of water rights, engineering modifications).
Gulf Coast wetlands provide wintering habitat for many North American waterfowl, so prospects for climate change here is of great interest.
Globally, average sea level has risen from four to eight inches over the past century, due mostly to thermal expansion of the warming oceans and melting of land ice. Climate models anticipate a further sea level rise of 18 to 20 inches by 2100, and more thereafter.
The rate of sea level change along the U.S. coast has varied from place to place because of differences in vertical movements of land, alluvial deposition, and land subsidence from extraction of water or petroleum. In historic times, relative sea level rise has been greatest in Louisiana, high in Texas and New Jersey, and intermediate along the Mid-Atlantic coast.
With a projected 18- to 20-inch rise in sea level, land loss along the U.S. coastline, without additional shoreline protection, has been estimated at: Mid-Atlantic Coast 900 square miles, Louisiana 1,350 square miles, other Gulf areas 900 square miles, and Pacific Coast 550 square miles. Clearly, humans and wetlands will increasingly compete for space in coastal zones, because a 24 percent growth in U.S. coastal county residents is predicted by 2025.
Between 1956 and 1990, Louisiana coastal wetlands were lost at a rate of 25 to 40 square miles per year. About 40 percent of the nation's brackish and freshwater coastal wetlands are found in Louisiana, where seasonal flooding of the Mississippi River successively created six distinct deltas over the last 7,000 years. During the last century, however, dam construction on the upper Mississippi has reduced the river's sediment load by about 50 percent, and the construction of levees has greatly reduced flooding. Faster main channel flow also means that less sediment settles out where it can build marshes. So, currently, marsh building cannot keep pace with sea level rise.
Extensive loss of habitat in the Gulf Coast region would affect species of concern like lesser scaup and northern pintail. Mid-continent lesser snow geese also winter here in large numbers, and the great majority of the world's redheads depend on shoal grass in the Laguna Madre. Freshwater habitats near the coast are limited and dependent upon uncertain precipitation. In recent decades, flooded rice fields have greatly augmented natural marsh habitats in these regions, but rice agriculture along the Gulf is on the decline in the face of tough competition from other rice-growing regions. If Gulf region coastal habitat losses are severe enough, with few options for redistribution of birds inland, wintering waterfowl could be in trouble in cold years when they concentrate at the southern end of the flyway.