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, Minn.

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, Minn. "Even for people who are making a decent living by farming, it's hard to leave that amount of money on the table."

Protecting vs. providing

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."

Draining increases flood risk

The decline of potholes will hurt more than duck hunters, said Steve Delehanty, wetland district manager for the Fish and Wildlife Service in Morris, Minn.

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.