Buffer str­ips have become a near household word in Minnesota since Gov. Mark Dayton launched his surprisingly passionate campaign for water quality in January.

He’s held community meetings, faced angry farmers and held firm against powerful agricultural interests that balk at the idea of requiring a healthy strip of natural vegetation along a third or more of the 70,000 miles of streams, rivers and ditches that meander through Minnesota. The heads of four state agencies have rallied behind him, as have hunters, anglers, bird lovers and conservation groups.

So even if Dayton’s initiative doesn’t pass the Legislature — where it’s stalled for the moment — buffer strips are now a rallying cry in the fight over agricultural contaminants that are killing off many of the lakes and rivers of southern and western Minnesota.

After all, buffers are a remarkably simple solution for a lot of pollution.

“Mother Nature has an awesome filter,” said Richard Schultz, a professor at Iowa State University who has studied the effects of buffer strips on one stream near Ames, Iowa, for two decades. “Let her do her thing, and she will do it.”

Buffer strips have been a common feature in farming for centuries. Barriers of grass, bushes and trees can block the rush of water from increasingly large rainstorms, slowing erosion on the land and in river beds. More important, they also stop most of the soil, phosphorus and nitrogen that the water carries off. Tall, stiff, prairie grasses on the edge of a field act as a wall to hold soil. And phosphorus, a nutrient that produces massive and sometimes toxic algae blooms in water, sticks to the soil and stops at the barrier. Plants also capture nitrogen through their roots, absorbing it and releasing it into the air before it reaches the stream.

Graphic: Natural buffers for agricultural lands Graphic: Natural buffers for agricultural lands

Buffers could take a significant bite out of the nitrogen pollution that comes from cropland runoff and groundwater — about a third of the total nitrogen load in Minnesota’s waters — according to a major analysis by the Minnesota Pollution Control Agency (MPCA).

And then there’s the rest of the ecosystem. Dayton’s initiative got its start at a pheasant summit late last year called to address the rapid decline of the popular game bird. The easiest solution, hunters told him, would be to enforce a long-standing state law that would restore badly needed habitat along water — buffer strips. They would help not only pheasants, but also bees, butterflies and other species­ that are rapidly disappearing from a landscape dominated by corn and soybeans. Aquatic life, including fish, also would benefit from cleaner, cooler water and more abundant food.

Dayton announced his plan in January. He called for legislation to beef up the existing law by adding consistent statewide standards, stronger enforcement by the state and a plan to map all the streams and rivers that should have buffers, adding 125,000 acres to the total. The vast majority of drainage ditches would not be included.

Minnesota needs a new law, he said, because the one that’s been on the books for years is confusing and poorly enforced by local authorities.

That’s especially true in regions of the state where buffers are needed the most.

A recent MPCA survey found that in the forested northeast part of the state, 94 percent of streams and rivers are fully protected by perennial vegetation. In the central area, where forest transitions to agriculture, the number drops to 60 percent. And in southern counties, where row crops cover up to two-thirds of the landscape, only 43 percent of the streams had buffers of mostly perennial plants.

“I was shocked at how right Dayton is on this,” said Darrel Mosel, a Sibley County farmer and a strong proponent of buffers and conservation. Since he first heard of Dayton’s proposal, he’s started looking closely whenever he drives through corn country. Sometimes, he said, “they are farming one inch from the creek.” He despairs of ever cleaning up Titlow Lake near his home in Gaylord.

“It’s the most beautiful lake in the entire state,” he said. “But thanks to farm water, it’s mostly dead.”

Farm lobby

But Mosel is a minority among farmers and the big organizations that represent them at the Capitol. The Minnesota Corn Growers Association, the Minnesota Soybean Growers Association, the Minnesota Farmers Union and the Minnesota Farm Bureau all came out against Dayton’s proposal. They said farmers recognize the need for buffers, and most plant them voluntarily already. Dayton’s plan would be a massive government reach into the rights of property owners, they said, with a “one size fits all” approach and confusion about where it would apply.

“Farmers are asking for clarity and uniformity so they can go out and do the right thing,” said Doug Peterson, head of the Farmers Union.

Some of those criticisms have been addressed in a proposed amendment by Sen. John Marty, chair of the environment and energy committee, but even so the governor’s bill has stalled for now.

“I think there is an outside chance it could pass this year,” said Marty, DFL-Roseville. “We haven’t heard the end of it yet.”

Schultz, the researcher, said farmers are right to question a blanket solution. Twenty-five years of research on central Iowa’s Bear Creek have proved that, to be most effective, buffers must be designed to fit the site. Downward slopes need wider buffers, and perhaps a basin to hold water, while uphill slopes need narrower ones. The types of plants matter a lot: Some grasses lie flat and allow water and pollutants to flow over them. Tall, deep-rooted prairie grasses stand up to the flow.

And the whole stream has to be protected to make a significant difference in pollution loads, he said.

“All you need is a couple of miles of bank erosion and you get tons of sediment coming in,” he said.

The Le Sueur River watershed in south-central Minnesota is a case in point. About two-thirds of the streams and rivers within the 1,000-square-mile watershed are protected by buffers of at least 50 feet, according to the Environmental Working Group, which conducted a major analysis last year. Still, tons of dirt from that one watershed flow into the Minnesota River and then into the Mississippi before dropping out into Lake Pepin. “The erosion that has occurred in the last 10 years is absolutely incredible,” said Pat Baskfield, an MPCA hydrologist who lives on the Watonwan River. “It looks like a bulldozer went through it.”

Even perfect buffers wouldn’t fix the problem, Baskfield said. Most drainage ditches don’t require buffers because they were built before 1977, and drain tiles beneath the fields bypass buffers entirely, dumping contaminated water directly into waterways. The state estimates that 37 percent of the nitrogen pollution in lakes and rivers comes from drain tiles.

But researchers on the Bear Creek project are now designing tile drainage systems that run contaminated water through buffers as well, and others are devising other solutions.

“It’s not going to result in fishable, swimmable waters every place in southern Minnesota,” Baskfield said. “But you have to start somewhere.”