“The old–timers,” says Dan Severson, “they can’t remember a drier summer.”
Severson, the manager at Quivira National Wildlife Refuge in Kansas, calls the drought gripping the south–central United States “the worst in modern memory.”
Forget memory, says Dan Alonso, manager at Aransas National Wildlife Refuge in Texas. It’s been 223 years since the region has been this dry—and that’s from Columbia University researchers who used dendrology (the botanical study of trees) to date the most recent drought of this magnitude to 1789.
There’s no end in sight, either. Meteorologists predict the region—extending from southeastern Colorado and eastern New Mexico across southern Kansas and through Texas to the Gulf of Mexico—will remain dry through this summer.
The dryness is impacting the southern portion of the Central Flyway, the winter grounds for millions of migrating birds, ducks and cranes—including the whooping crane, the tallest and rarest bird in North America. “All our fresh water holes are entirely dry,” Alonso says of Aransas Refuge, the December–to–March home to the continent’s only natural flock of whooping cranes.
At Quivira Refuge, Severson says, the drought started in September 2010, when the refuge received half an inch of rain in a month that typically has more than two inches. Rainfall in June 2011 was three–quarters of an inch, down from the usual four inches. July was no better, and weeks of 100–degree days set in, causing rapid evaporation. The deficit has not been made up since.
Severson estimates 100 acres of wetlands are left at Quivira Refuge, where 7,000 acres normally are underwater. The 3,500–acre Big Salt Marsh, usually thigh–deep in water, was dry in December 2011 except for a few puddles and Rattlesnake Creek barely trickling in.
While droughts are difficult, they are part of the natural cycle, Severson says. He estimates major droughts hit the region every 20 years or so and less extreme dry periods come every seven to 10 years.
The dehydration has advantages for marshes, he says. It allows for more oxygen to reach the soils, which is essential for the decomposition and regeneration of food sources for invertebrates and animals on up the food chain.
Drought also gives refuge staff members a chance to eradicate invasive plants as well as carp and other invasive fish. Those fish eat vegetation that other animals rely on and muddy the waters, preventing sunlight from reaching the plants at the marsh bottom.
That said, once a drought is over, full wetlands are a great relief—to birds, plants and refuge staff alike.
Severson is concerned about the drought’s severity, but he knows there is nothing anyone can do. He attributes it to La Niña, a phenomenon that cools the surface waters of the Pacific Ocean. When La Niña strikes, the central United States is dry. La Niña usually occurs every two to seven years and persists for about a year. But this one is predicted to continue through 2012.
Even so, water is plentiful north of Quivira Refuge. And while migrating birds generally go where the water is, cold winter temperatures are forcing them south, ultimately to the Gulf Coast, where most remaining water is in salty bays.
Birds can handle some salinity in water, but not at the concentrations caused by the drought, says Alonso. To compensate, Aransas Refuge this winter is revitalizing old windmills to pump fresh ground water into ponds. And to help provide food for the whooping cranes, it is scheduling prescribed burns on 9,000 acres to open up foraging land.
Food is scarce at Quivira Refuge, too, where Severson says the drought has hurt agricultural crops, an essential food source for waterfowl.
Most water left on the refuge is in Little Salt Marsh, and that’s where most of the birds are concentrated. Normally the refuge holds 500,000 to a million waterfowl, Severson says. “Now we have about 100,000, and they’re not staying very long—days instead of weeks.”
If historical patterns prevail, Severson says, flooding will follow the drought. But before that happens, he predicts, Little Salt Marsh will dry out completely.
Jennifer Anderson is a frequent contributor to Refuge Update.
