MINNEAPOLIS (AP) -- The humble name given to "prairie potholes" -- the ponds, wetlands and small lakes dimpling Minnesota and the eastern Dakotas -- belies the mounting concerns here and nationally about their disappearance from the landscape.
Potholes are considered key habitat for almost 200 species of migratory birds. But with federal inducements to plant more crops and the financial rewards of renting out the land, many farmers are ending land-preservation agreements.
With a federal report warning of the need to protect them, the Minnesota Department of Natural Resources is doing flyovers to investigate whether potholes are being drained illegally.
At stake is "arguably the most endangered ecosystem in the world," said Rex Johnson, a wetlands expert and wildlife biologist for the U.S. Fish and Wildlife Service in Fergus Falls.
The U.S. Government Accountability Office warned last month that the Fish and Wildlife Service is falling behind in protecting the pothole region. The study estimated that it will take 150 years and billions of dollars for the agency to acquire enough land to sustain healthy bird populations.
The study also noted that land prices have quadrupled in many areas in the past decade and that landowners can do better renting their land than letting it stay in a natural state.
"The pressure is immense right now," said Brent Olson, who owns about 1,000 acres near Ortonville. "Even for people who are making a decent living by farming, it's hard to leave that amount of money on the table."
Millions of prairie potholes were drained during the past century, but those that remain -- an estimated 420,000 in Minnesota and 2 million in the Dakotas -- still store and purify vast amounts of water that would otherwise overload rivers with runoff and sediment.
Olson, a Big Stone County commissioner and writer, farmed for three decades and now rents his land.
Farmers in the area signed 10- to 15-year conservation agreements in the 1990s to set aside grasslands and prairie potholes for wildlife habitat, he said, but many are converting the land back to crops as soon as those contracts expire.
Conservation programs pay farmers to set aside grasslands and potholes for wildlife, but commodity programs encourage farmers to use as much cropland as possible -- offering disaster payments, crop insurance and other subsidies.
With corn in demand for ethanol and wheat prices spiking because of drought, farmers are converting more of the potholes to cropland.
"It's a perfect storm of events that are going to be detrimental to waterfowl," said Jim Ringelman, director of conservation programs for Ducks Unlimited in the Dakotas and Montana.
"Farmers want to protect nature," Olson said. "But if it interferes with providing for their family, nature's going to come out second."
The decline of potholes will hurt more than duck hunters, said Steve Delehanty, wetland district manager for the Fish and Wildlife Service in Morris.
Potholes are nature's best filters, he said, preventing floods by holding vast amounts of water until it evaporates or seeps into the soil to regenerate groundwater supplies. Draining more of them into rivers and lakes will worsen water quality and increase flood severity, he said.
Potholes most at risk are temporary wetlands that may hold only a few inches of water for a few weeks each spring, Delehanty said.
During that short time they unleash a rush of nutrients that provide a rich diet for nesting birds and their newly hatched offspring, he said.
Once the wetland dries up for the year, said Delehanty, the waterfowl move to larger and permanent wetlands for summer feeding and growth.
Driving across the landscape of Pope County, DNR conservation officer Kurt Nelson can find a small marsh or some form of wetland vegetation beyond almost every dip in the road.
But the view is deceiving. Most of the ponds have poor water quality because too much fertilizer or feedlot wastes have drained into them from nearby fields.
"It's horrible to say, but the water looks like chocolate milk, and there's no vegetation growing in it," Nelson said. "Birds need something to eat, so that's why you won't see ducks here."
To illustrate, he stopped at one wetland and lowered a saucer-size white disc on a string into the water. Four inches below the surface, it could no longer be seen.
Nelson and others don't blame farmers for the problems but question the federal farm programs that seem to work at cross-purposes.
Doug Hertz, a rancher and farmer in the heart of pothole country in central North Dakota, said he understands the importance of wetlands and has enrolled nearly 1,000 acres in various conservation programs over the past two decades.
When those contracts expired last month, Hertz said he didn't renew any of them. Weeds have overtaken much of the land, he said, and it needs to be reseeded with hay or converted to grow wheat.
Hertz said that he respects the concerns of duck hunters who are alarmed about losing waterfowl habitat, but that he and many of his neighbors are ready to return their land to crop production.
"The economics of farming and ranching dictate that you've got to do this," he said.