By Mark Petrie, PhD, and Virginia Getz
Most Ducks Unlimited members are already aware that much of the Prairie Pothole Region of the United States and Canada is in the midst of a severe drought. By many accounts, conditions in the Duck Factory haven't been this dry since the 1980s. To make matters worse, another drought, outside of the prairies, is gripping some of the most important waterfowl migration and wintering habitats in the West.
As of this writing in mid-July, more than 25 percent of the western United States was experiencing exceptional drought, the most severe category possible according to the National Drought Mitigation Center. Three regions of particular importance to waterfowl—we'll call them the Big Three—are located within these exceptionally drought-stricken areas. They include the Central Valley of California; the Klamath Basin, which lies along the California-Oregon border; and Utah's Great Salt Lake. Together, these landscapes support the majority of the migrating and wintering waterfowl in the Pacific Flyway.
In a typical winter, the Central Valley hosts between 6 and 8 million ducks and geese. Most of the birds that reach the Central Valley follow either of two migration routes. One passes through the Klamath Basin and the other runs through the Great Salt Lake. In spring, waterfowl follow these same routes on their way back to the breeding grounds. As we'll see, the cumulative effects of drought in the Big Three may pose significant challenges for Pacific Flyway waterfowl this fall and possibly into the winter and beyond.
So how bad is it? In the Klamath Basin it has never been worse. The area is home to the Lower Klamath and Tule Lake National Wildlife Refuges, which were once among the most important fall staging areas for waterfowl in North America. Both refuges are located within the boundaries of the Klamath Irrigation Project, created by Congress in 1905, which today supplies water to 240,000 acres of irrigated farmland in Oregon and California. The irrigation project's main water source is Upper Klamath Lake, which also supplies water to the refuges. The lake is home to two endangered species of sucker fish, so water levels must be maintained at or above a minimum level to support these fish populations. This spring, lake levels reached a record low, and no water was allocated for either agriculture or the refuges.
The impacts on wetlands and other wildlife habitats have been catastrophic. Lower Klamath refuge once provided 25,000 acres of well-managed wetlands for waterfowl and other wildlife. As of this writing, the refuge is down to a mere 600 acres of wetlands, which are rapidly disappearing in the summer heat. Tule Lake refuge's largest wetland, the famous Sump 1A, is little more than a 9,000-acre mudflat with some shallow standing water. These conditions are perfect for a botulism outbreak, and farmers and refuge staff are currently working together to completely drain the wetland before large numbers of waterfowl arrive. This is the second consecutive year that Sump 1A has been starved of water, and a botulism outbreak there last summer killed at least 50,000 waterfowl.
Conditions aren't as bad on the Great Salt Lake, but they are bad enough. Since 1847, the lake's size has averaged about 1,700 square miles. The lowest lake elevation ever recorded was in 1963, when water covered only 950 square miles. That record will likely be broken this summer, with the lake expected to fall 45 percent below its normal level.
Waterfowl habitat in the Great Salt Lake falls into one of three categories. The first is managed wetlands, encompassing about 160,000 acres on both public and private lands. These habitats, which provide the greatest concentrations of food for waterfowl, are expected to be reduced by about one-third this fall. The second category includes nearly 350,000 acres of unmanaged wetlands, most of which will be dry. The third category is the open waters of the lake, which many waterfowl use and which support brine shrimp—another important food source for ducks. Unfortunately, as the lake shrinks and salinity levels increase, the abundance of brine shrimp declines.
Ducks that migrate through the Klamath Basin and Great Salt Lake begin reaching the Central Valley of California as early as August, with numbers building through December. Most waterfowl and other wetland birds that winter in the region rely on two major habitat types: managed wetlands and rice fields that are flooded after harvest. In normal years, the waterfowl habitat base in the Central Valley includes about 210,000 acres of managed wetlands—largely on public lands and private duck clubs—and 340,000 acres of winter-flooded rice.
At this point, no one is certain how much water will be available in the Central Valley this fall. Normally, most managed wetlands are flooded by late October. The best guess is that only half of these wetlands will receive water. The rest will depend on fall or winter rainfall. The outlook for winter-flooded rice is considerably worse. Only about 80,000 acres—or 25 percent of the normal total—are expected to be flooded, and no additional water will be available to maintain flooding. Thus, timely precipitation will be needed to increase the acreage of winter-flooded rice and avert potential food shortages for waterfowl.
While droughts are never welcomed, they can help bring important conservation priorities into focus, and the Big Three share some important challenges that the drought makes clear. On these semiarid landscapes, waterfowl and other migratory birds rely heavily on intensively managed wetlands and agricultural habitats that must be intentionally flooded each year. In the West, few issues are as contentious as water diversions and the water rights that govern their allocation. The water resources that are used for waterfowl habitat management have proven to be highly vulnerable during the current drought.
DU is actively working on several fronts to meet the challenges posed by drought in the Big Three and other areas of the West. Top priorities include public policy work to help maintain water supplies for wetlands and agricultural habitats. DU will also continue to partner with government agencies and private landowners to manage wetlands to provide high-quality habitat for wildlife while using water as efficiently as possible. Finally, improving water security for waterfowl and people will depend on restoring populations of endangered fish species in places like the Klamath Basin and Central Valley. Some of these species have declined due to the loss of important spawning and nursery habitat in wetlands. DU is working with a consortium of conservation groups, water districts, and agricultural partners to help fish populations recover. Wetlands conservation is our specialty, which means we have a unique role to play in helping all water users on these landscapes.
Although we shouldn't underestimate the seriousness of this drought, it's important to remember that waterfowl evolved over thousands of years with highly variable wetland conditions on their breeding, migration, and wintering areas. They adapted by being mobile and seeking out habitat and food wherever it might be available. Although we can't change the weather, we should take heart in the birds' resiliency. Our responsibility is to make sure that the poor habitat conditions created by this year's drought don't become permanent.
Dr. Mark Petrie is director of conservation planning and Virginia Getz is director of conservation programs in DU's Western Region.