Kathy Connell never thought she'd see it in Minnesota: deforestation.

But last year she watched with dread as the pine trees surrounding her tiny vegetable farm 60 miles northwest of Brainerd were torn out and heaped into piles of slash.

Now she fears what might come next — huge potato fields, aerial pesticides and contaminated drinking water. Already her neighbors are paying thousands of dollars to dig deeper wells. "To me the earth is a God-given gift," she said. "It's morally wrong to poison the water."

The forests of central Minnesota — a region that has the state's highest deer densities and that protects a largely pristine but vulnerable aquifer — are being cleared at an accelerating pace, and regulators are scrambling to find a way to protect them.

It's part of a bigger, mostly invisible transformation in the large watershed that drains into the upper Mississippi River, and which supplies drinking water for 1.7 million people in the Twin Cities. Since 2006, some 275 square miles of natural land in the Upper Mississippi watershed has been converted to row-crop agriculture, according to a new University of Minnesota analysis — much of it sandy soils and forests where no one ever expected to see farming.

"We didn't see this coming," state hydrologist Darrin Hoverson said at a recent conservation conference. "And we cannot see where it's going to go."

This rapid transformation is adding urgency to a growing debate: Should Minnesota use tax money devoted to clean water to fix its polluted lakes, streams and wetlands, or to protect what remains undamaged?

"Let's avoid the situations we've seen in other parts of Minnesota," said Rich Biske, freshwater conservation director for the Nature Conservancy in Minnesota, which is studying how to preserve the watershed and protect the Mississippi. "It's incredibly challenging to go backward."

Tainted well

The town of Park Rapids, about 20 miles north of Connell's farm, is a case in point.

Its economy relies on a mix of agriculture and tourism around the popular lakes and top-notch hunting grounds that stretch southeast to Brainerd. But for decades its residents have watched as the levels of nitrogen, which can be toxic for infants at high concentrations, inched ever higher in their drinking water.

The town sits on the north end of the Pineland Sands Aquifer, a source of drinking water for residents and irrigation for farm fields that surround the town. But the aquifer is quite shallow and covered with sand left behind by glaciers, which leaches everything from the surface straight into the groundwater.

Last year, after lengthy discussions, Park Rapids drilled a new, deeper well and installed an additional water treatment system, at a cost of $3 million. State and local officials say they can't specify where the nitrogen is coming from. Possible sources include septic systems, natural sources and farming — especially the chemically demanding potatoes that supply the local French fry factory.

"Anything that gets spilled ends up in the water," said Scott Burlingame, utility supervisor for Park Rapids. "I'm not going to sit here and point my finger at farming. We need water, we need food, too."

Nonetheless, the state Pollution Control Agency estimates that, statewide, agriculture and fertilizers contribute three-fourths of the nitrogen that pollutes Minnesota's lakes and streams — 90 percent in the Minnesota River watershed and 50 percent in the upper Mississippi.

Now, in an irony that is not lost on state regulators, the effort to protect Park Rapids could result in simply moving environmental risks to other areas of the aquifer.

R.D. Offutt Company, a Fargo-based firm that is the nation's largest potato grower and has extensive operations in Minnesota, is expanding its fields in order to reduce its impact on water.

Instead of planting potatoes every third year, in a rotation that usually includes corn and soybeans, as often as possible it will plant them every fourth.

"If we can lengthen the rotation, our inputs will be less," said Nick David, an Offutt agronomist based in Park Rapids.

Over the years the family-owned company, which is also by far the largest irrigator in Minnesota, has made major strides in conserving water and agricultural chemicals, officials say, including a 10 to 15 percent reduction in nitrogen fertilizers.

"We've been here for 60 years," said Anne Struthers, Offutt's communications manager. "We have a responsibility to continue to use the land sustainably."

But for now, that means buying commercial forest land — up for sale by the Potlatch Corp. — and turning it into farmland. According to state figures, Potlatch has sold more than a third of its nearly 50,000 acres of commercial forest in the region. Hoverson said 12,000 of those acres already have been or soon will be converted to farming, and another 20,000 could be. In addition, many thousands more held by other landowners could be sold if the price were right, he said.

Surge in irrigation

The pace of this transition can be seen in the explosion of requests for irrigation permits on land that was forested until recently. In 2012, Offutt was granted three permits by the Minnesota Department of Natural Resources (DNR), then 26 more in the following two years. Other farmers received three more. Today, Offutt has 57 irrigation applications pending — a volume that state officials say they find troubling. They are now looking into additional ways "to get a handle on landscape-wide protections," said Chris Niskanen, director of communications for DNR.

Irrigation makes farming possible in this historically dry region, but it also helps drive water contamination. Already, about 5 percent of the private wells in the area have nitrogen concentrations exceeding the federal health limit, according to a survey by the Minnesota Department of Agriculture.

Connell fears that hers might be next.

She and her husband live on his Social Security and what they earn from selling the vegetables they grow on land alongside the Red Eye River. Connell said wolves, deer and bobcats are regular visitors in the nearby forested lands, and she's foraged for blueberries and other edible plants that grow under the trees.

Four years ago, when a new crop of trees was planted, she thought they'd be safe, she said. But those trees were torn out last year, and a 12-inch irrigation pipe was installed.

"I know they are trying to do some things," she said of R.D. Offutt's mitigation efforts, but she doubts it will suffice to protect her well, which has always tested well below the nitrogen limit. A deeper one would cost at least $5,000, "and how long will that last?" she said.

The state is accelerating efforts to monitor and manage water use and contamination in the region. The Agriculture Department, along with Offutt and outside researchers, is tracking the effect of a new potato field planted over pristine groundwater, a unique opportunity to study the precise impacts of different farming techniques.

The community around Park Rapids and the state have formed a regional council to manage groundwater issues, an effort that has reduced water use and inspired a water recycling program at the town's French fry plant. And last year, the DNR quickly snapped up about 900 acres of Potlatch land to preserve a stand of ecologically valuable jack pines that are rapidly disappearing.

Still, the pressures on water are increasing statewide. Irrigation permit applications have averaged roughly 550 in each of the last two years — 10 times higher than before.

Biske, of the Nature Conservancy, said it's much easier and cheaper to protect clean water and healthy forests than it is to repair them later. Over the next 20 years, Minnesota will spend an estimated $2.5 billion from the 2008 Legacy Amendment to protect clean water, yet the share of lakes and streams deemed clean enough for fishing and swimming will rise from 60 percent now to just 67 percent, according to John Linc Stine, commissioner of the Minnesota Pollution Control Agency.

"I don't think it's what people thought they were voting for," he said.

Josephine Marcotty • 612-673-7394