Minnesota's top environmental officials and conservation groups Tuesday announced an ambitious 25-year plan to preserve a piece of the vanishing prairie that once stretched like an ocean across two-thirds of the state.

State and federal agencies, together with 10 leading conservation groups, will combine resources to acquire or protect more than 2.2 million acres in a network of connected native and restored prairies, wetlands and grasslands along the state's western edge.

While it would not come close to the 18 million acres of prairie that made up much of Minnesota 150 years ago, it would be large enough -- and in just the right places -- to function as an irreplaceable resource for clean water, wildlife and carbon sequestration, they said. It also would literally provide the seeds for future conservation across the Great Plains.

The $3.5 billion project was announced Tuesday by Tom Landwehr, commissioner of the Department of Natural Resources, and officials from the U.S. Fish and Wildlife Service and ten conservation groups.

Landwehr said only 1 percent of the state's 10,000-year-old native prairie remains today, scattered in fragments across the western half of the state. The little that is left has been untouched mostly because it's on land that is too steep or too rocky to farm. But the relentless pressure of development, rising commodity prices and advances in agricultural technology means the rest may soon disappear as well, he said.

"We can see the trend line of where this is going," he said. "We are not going to get ahead of it, but we have to get as much protected as we can."

Landwehr said Minnesota can use sales tax revenue generated by the Legacy Amendment to leverage federal and private funds to buy land and pay private landowners permanent easements to keep land in grass forever. In all, the plan calls for $1.1 billion in Legacy funds plus $2.5 billion from other sources over the next 25 years.

Minnesota officials said the agreement is significant because it means that state and federal agencies and such leading conservation groups as the Nature Conservancy, Pheasants Forever and the Audubon Society have all agreed to execute the same plan, greatly increasing chances of success.

All the groups signed a memorandum of understanding to that effect on Tuesday.

Grasslands, whether native prairie or less environmentally valuable pasture, are critical to preserve clean water and prevent soil erosion. In contrast to annual row crops, perennial prairie plants have roots that extend many feet into the ground, filtering water and soaking it up before it runs off the land.

"Water purification and filtration and flood retention are important for grasslands, but prairies are best," said Steve Chaplin, director of prairie conservation for the Nature Conservancy.

But, he said, the most important environmental aspect of the project is preserving the thousands of plant and animal species that are disappearing as fast the prairie.

"This is our ark of prairie plants and animals that have the potential for being used to re-establish new prairies, and that have the best chance of surviving in the long run," he said.

Grazing livestock

The project also incorporates a new definition for preservation. Recognizing that prairies evolved with bison as a vital part of the ecosystem, the state would encourage grazing by livestock on protected prairies to keep them healthy, help create a diversified agricultural economy and produce revenues in local communities.

It would be boon for the livestock industry, which cannot compete for land while corn and soybean prices are soaring. This year, corn planting in Minnesota will cover an estimated 8.7 million acres, up 7 percent from last year, according to federal estimates.

In all, the plan calls for 261,387 acres to be acquired by government or conservation groups; 485,097 would be protected by long-term easements, and 1.5 million would be protected by short-term contracts. For the state's 235,000 acres of remaining native prairie, 70 percent would be protected by easements provided to private landowners and 30 percent would be acquired.

In addition to the protected grasslands, the plan specifies protected status for 10 percent of environmentally sensitive land across the state, particularly along streams and rivers and on steep slopes. That would help offset what is expected to be a major reduction in land now protected by the federal Conservation Reserve Program.

John Jaschke, head of the state's Board of Water and Soil Conservation, said in the next five years about half of the Minnesota acres now in that program will likely be turned back to row crops because of high commodity prices and reduced federal set-asides.

"At least 10 percent of the landscape should be in native perennial coverage, to make them more wildlife friendly and to allow native species to persist," Chaplin said. "But we are not even close to that 10 percent level."

Josephine Marcotty • 612-673-7394