Agriculture is eating into central Minnesota's forests so aggressively that state regulators and a prominent legislator are sounding the alarm about threats to wildlife habitat and a large, sensitive aquifer that stretches below parts of four counties.

The latest case is a 1,500-acre project in Cass County, which triggered a contentious legislative hearing last month over the owner's plans to grow potatoes for McDonald's and other customers on land that was covered with trees just 10 years ago.

In recent years, 5,000 to 6,000 acres of pine forests in Cass, Wadena and neighboring counties have been cleared for chemically intensive row-crop agriculture, and state officials say nearly 100 square miles of timber land now owned by Potlatch Corp. is at risk as the company divests itself of commercial forests in Minnesota.

Similar tensions could face the entire state faces as it copes with persistent water contamination and overuse, regulators say. The risk is especially worrisome along the border between traditional farm lands and the forested areas in central Minnesota, where contaminants can percolate straight through sandy soils into groundwater, and from there to trout streams and popular lakes.

Several local communities already face huge costs to taxpayers in their struggle to find drinking water that is not contaminated with agricultural fertilizer.

"Groundwater and drinking water have not been issues until recently," said Rep. Jean Wagenius, DFL-Minneapolis, chair of the House committee that held hearings this month. "But that's the public conversation I want to have."

R.D. Offutt's project in Cass County is a case that shows what's at stake and the powerful forces driving land conversion. It also has focused the legislature's attention on an increasingly difficult question on the environmental impacts: Who should pay?

Offutt, based in Fargo, is the nation's largest potato grower and a supplier to McDonald's and other food companies. The Freshwater Society, a Minnesota environmental group, found in a recent analysis that Offutt is the largest single irrigator in the state, with rights to pump up to 12 billion gallons of water per year on 30,000 acres.

Recently, it acquired 1,459 acres of cleared commercial forest land from Potlatch, pulled out the stumps, drilled four deep wells and installed high-capacity pumps.

"I was speechless," said Jeff Broberg, a geologist who sits on a legislative advisory committee and saw the work underway this summer while on a site visit. On one side of the road was an aspen forest full of birds and blueberries, he said. On the other, he said, "the habitat destruction was complete. It might as well have been pavement after that."

Rising land prices

At the October hearing, Keith McGovern, an Offutt manager, said the company does not intend to increase its potato production. Offutt bought the land so it could improve crop rotation on other fields — which can be better for the soil and the environment — without reducing its overall potato supply to a plant it co-owns in Park Rapids.

But Cass County Land Manager Joshua Stevenson said the strategy still reflects daunting agricultural economics that conflict with forest conservation. "We know what they are paying," he said. "It's way above anything we've ever paid for forested land."

Offutt paid about $2,500 per acre, while the county usually pays roughly $1,500, he said.

"How did you get to a point where it's cheaper to buy forested land at $2,500 an acre, and spend hundreds of thousands to clear it and drill wells?" Stevenson asked. The answer, he said, is that soaring prices for corn and soybeans have made it harder for Offutt to rent land from farmers.

"It's cheaper for a company like [Offutt] to bulldoze trees," Stevenson said. "A lot of this is coming down to [public subsidies] for corn and ethanol."

That's partly true, a company official said, but Offutt also has fewer options for land because potatoes require the sandy soil so well known in central Minnesota.

The Pineland Sands Forestland covers 1,000 square miles that are largely unpopulated but widely used for hunting, fishing and recreation. It's also above part of the Pineland Sands Aquifer, which supplies nearby lakes, streams and rivers and is still pretty much uncontaminated, said state environmental officials.

The forest, much of it commercial timberland, has long protected the water in the region; as long as the land is 75 percent trees, ground and surface waters will remain pristine, said John Ringle, Cass County's environmental director.

But the aquifer and the sandy soils also make the land ideal for potatoes. However, they require fertilizers and regular pesticide and fungicide treatments, and frequent irrigation that can wash those chemicals down through the sand and into the groundwater.

Drinking water

Decades of fertilizer use in neighboring agricultural regions are starting to produce dangerous results in local drinking water. In Park Rapids, located in the potato and corn region of southwest Hubbard County, water is showing rising levels of nitrates from nitrogen fertilizer, which can cause a potentially lethal condition in infants called blue baby syndrome. Park Rapids plans to install new, deeper wells and a water treatment plant that will cost $2 million.

McGovern, who testified for Offutt at the legislative hearing, said the company has a vested interest in minimizing chemical use and is required by McDonald's and other buyers to use environmentally friendly farming practices. Offutt is also working with Park Rapids to reduce fertilizer use around city wells.

"As a steward of the land, I need to do everything I can to prohibit transfer of nitrogen into aquifers, and I believe I'm doing that," he said.

But when Wagenius asked whether Offutt should pay for the cost of contaminated drinking water, he said the source of contamination is not clear.

"Do you believe you have responsibility for nitrogen showing up in those wells?" she asked.

"I'm not the right person to answer that question," he said.

Even the best farm management is unlikely to protect the sensitive aquifer, state officials said — a point Wagenius made directly in a letter to McDonald's, challenging its claims of following environmentally friendly policies.

"[This] method of growing potatoes … cannot avoid contaminating the groundwater or wasting natural resources on this particular converted forest land," she wrote.

McDonald's officials did not respond to requests for comment.

The Minnesota Department of Natural Resources (DNR), which gave Offutt temporary permits to irrigate, will monitor its water use and the impact on nearby surface water and wells, said Darrin Hoverson, a DNR hydrologist.

But despite the rising amount of land conversion, the state has never denied a permit because of potential risk, Hoverson said. "That may be something for the future," he said.

Meanwhile, both the state and Cass County are seeking funding from the 2008 Legacy Amendment to buy Potlatch land before it's sold to others. DNR officials said they have identified 11,000 acres of ecologically valuable land in the Pineland Sands region that the agency would like to protect.

They're asking for $4.2 million in taxpayer money to buy 2,000 of them.

Josephine Marcotty • 612-673-7394