– In a patch of hilly, old-growth woods preserved by the state as a living museum, Bob Djupstrom and Ellen Fuge stepped carefully around wild ginger, trout lilies and other native plants carpeting the forest floor.

Townsend Woods is one of Minnesota’s 160 Scientific and Natural Areas (SNAs), places that are considered so precious that only the lightest human touch is permitted. Camping, ­picnicking and swimming are not allowed. Visitors are prohibited from walking a dog or picking berries. They can take photographs or simply sit beneath the canopy of virgin oak, sugar maple and basswood to look and listen.

“These are jewels of the natural world,’’ Djupstrom said. “They should be left alone.’’

Despite growing opposition, the Department of Natural Resources plans to open more of the sites to hunting and trapping. Townsend Woods is one of 10 under review for such a change, while three other SNAs, all south of the Twin Cities, were quietly approved as hunting grounds starting in 2012.

“It’s so ridiculous to mess with these sites,’’ Fuge said. “The whole point is to protect their natural processes.”

Fuge and Djupstrom are retired Department of Natural Resources managers who fostered the SNA network during long careers. Now they are fighting from outside the agency to block what they consider an attack on the program’s longtime mission — protecting the biological integrity of some of Minnesota’s ecological treasures.

SNAs originated in the early 1970s to isolate and preserve pieces of the state’s natural heritage, including rare species and unique geologic features.

“This is a Minnesota string of pearls … where there is minimum disturbance,’’ said Tom Casey, a Twin Cities lawyer and naturalist who takes weekend trips to SNA sites around the state.

DNR backs off plan

SNA Program Supervisor Peggy Booth said public opposition to increased recreational use of SNAs has prompted the DNR to back off its earlier plans to systematically review them for hunting and trapping. But some have been opened up, and others may be, in part because the Legislature has tied funding for the program to the interests of sportsmen.

The Legislature criticized the SNA program in 2011 for limiting public use of the sites when it halved a special appropriation from lottery funds. And it mandated that any future SNA land acquisitions funded by the Legacy Amendment be tied to hunting or other recreational use, she said.

“It has been a public perception that SNAs are locked away and are not for the public,’’ Booth said. “I don’t think the resources have been put at risk with additional uses.’’

Some SNAs have always been open to hunting — including the 70 percent of SNA acreage that is in northern peat lands. But SNAs have always been treated as distinctly different from the state’s Wildlife Management Areas (WMAs), a substantially larger collection of preserved land designed with hunting in mind. Now the lines between the two are starting to blur. Just as the DNR wants to expand hunting and trapping in the scientific areas, it is also elevating natural preservation in the WMAs, Booth said.

Still, the DNR has a proposal to nearly double the SNA lands by expanding to 325,000 acres by 2099. Over the next 20 years, the target is to increase the acres devoted to SNAs by an average of 1,600 acres a year, with an emphasis on prairie. Booth said in a memo that the program’s purpose remains “to protect and perpetuate in an undisturbed natural state those natural features which possess exceptional scientific or educational value.’’

At stake are places like Blue Devil Valley near Granite Falls, an SNA now closed to hunting and trapping that supports one of the largest known populations of a rare lizard, the five-lined skink. In extreme southwestern Minnesota, the DNR has opened Prairie Coteau to hunting despite its being home to rare butterflies and burrowing owls. It has been described by the DNR as “one of the most important and stunning prairies’’ in the state.

Big Woods donation

Early boosters of the SNA program included the late Wally Dayton, who gave millions of dollars for sites to be acquired. Major supporters also have included Bruce and Ruth Dayton, the father and stepmother of Gov. Mark Dayton. They created the popular Wood-Rill Scientific and Natural Area in Orono with a gift of the so-called Big Woods that includes trees 120 to 400 years old.

Djupstrom, Fuge, Casey and others are pressing to move the SNA debate to the Legislature, where it can’t be controlled by DNR managers. They maintain that DNR Commissioner Tom Landwehr is exceeding his legal authority by expanding public uses on SNA land without legislative approval.

“They are going about it in a sneakier way and that’s wrong. It’s totally wrong,’’ Djupstrom said.

Djupstrom, who headed the SNA program for more than 20 years until 2006, said it should be up to lawmakers to decide whether more SNA sites are opened for hunting and trapping, especially at a time when many Minnesotans want more destinations were no hunting is allowed.

“The hunters already have lots of lands in Minnesota,’’ Casey said.

Booth said the agency has conformed to the law. This year it expanded public notification and opened up the review process for more public input. When the Izaak Walton League made the case to keep some areas closed to hunting and trapping, the agency listened, she said.

“We’ve definitely made decisions in some cases that extra uses can’t be tolerated,’’ Booth said.

Clint Miller, chairman of a citizens’ advisory committee to the SNA program, said so far increased hunting and trapping haven’t conflicted with SNA objectives.

According to Djupstrom, Minnesota has 12 million acres of land and water in public ownership, nearly all of them open to fish and game pursuits. The amount of SNA land off limits to hunting is far less than 40,000 acres.

“It’s so minuscule,’’ he said.

Fuge said that one of the best reasons to minimize recreational activity on SNA sites is to preserve an inventory of relatively undisturbed plant and animal communities for science. “It gives you a benchmark to see what nature is doing,’’ she said. “These are the only sites in the state that have this kind of protection.’’