But just as important is what will happen to prairie agriculture. Agricultural practices such as grazing and haying that leave grassland intact provide habitat for nesting waterfowl and other wildlife, and conserve accumulated carbon in prairie soils. In contrast, intensive annual cropping (e.g., for grains and oilseeds) is associated with lower waterfowl breeding success. Agricultural experts are divided about how prairie agriculture will change in the decades ahead, but one recent analysis by Agriculture Canada suggests that new areas of Alberta and Saskatchewan may become suitable for small-grain production in the future, which would be a negative development for waterfowl habitat.
The vast western boreal forest of Alaska and northwestern Canada may be among the regions most affected by climate change because of the greater temperature changes expected at high latitudes. Predictions include longer ice-free seasons, melting permafrost, increasing frequency and perhaps intensity of fires, and northward range shifts by plants, animals, and forest pests. Recent studies in Alaska and Siberia discovered that melting permafrost has contributed to drying of small wetlands and reduced habitat quality for ducks like scaup and scoters.
The biggest obstacle in predicting impacts of climate change on boreal waterfowl is our meager understanding of the basic ecology of boreal wetlands. We know little about what limits waterfowl populations in this remote region or the wetland food webs on which ducks depend. This is a serious knowledge gap because while several boreal duck species (scaup, scoters, and wigeon) are declining, resource development is expanding and northern climate is changing.
Along the Gulf Coast, wintering waterfowl could suffer substantial habitat losses. Oceans are rising due to thermal expansion and melting land ice. In 2007 the IPCC projected that with a global temperature rise of 3 degrees Celsius (5.4 degrees Fahrenheit)—a middle-range scenario—30 percent of the earth’s coastal wetlands would be inundated by saltwater. Vulnerability of coastal wetlands varies from place to place. In south Louisiana, where about 40 percent of America’s brackish and freshwater coastal wetlands are found, seasonal flooding of the Mississippi River historically created a series of deltaic wetlands. Today, dams on the upper Mississippi River have reduced sediment load by about 50 percent, and the construction of levees has greatly reduced flooding. Less sediment is available to build new wetland habitat, so coastal marshes are unable to keep pace with sea-level rise. During the past 70-80 years, more than 750,000 acres of coastal wetlands in southeastern Louisiana have already been converted to open saltwater.
In the Central Valley of California, higher temperatures are predicted to cause more precipitation in the Sierra Nevada Mountains to fall as rain rather than snow. More rapid runoff and earlier snowmelt would lead to higher winter flows but also increased competition for water during the summer. Refuges, duck clubs, state wetlands, and rice fields all depend on allocations of California’s managed water. If future winters in the Central Valley are indeed wetter than today, waterfowl may benefit. But the value of this flooding would depend on land use. If rice production declines (because of rising irrigation costs, for example), then winter flooding of agricultural land would be of little value to waterfowl. Reduced summer runoff also might contribute to concentration of toxic chemicals in estuaries to the detriment of wintering diving ducks.
Future impacts of climate change are less certain in the Mississippi Alluvial Valley. Scientists know the extent of winter flooding in the region affects body condition and winter survival of mallards. Presently, however, climate models offer contrasting predictions about future river flows, leaving us with little ability to predict flooding patterns.