March 01, 2007

Survey provides input on managing invasive plants

by K.C. Jaehnig

CARBONDALE, Ill. — Folks visiting Giant City State Park may not know a "foreign," invasive plant when they see it, but they know they don't like it.

"More than 70 percent of the visitors we surveyed said control of non-native, invasive plants was extremely important, but when we asked if they'd seen these plants in the park, 81 percent said, 'No,' and 64 percent thought they were not a problem at Giant City or only a slight problem," said Mae A. Davenport, an assistant professor of forestry at nearby Southern Illinois University Carbondale.

Park officials, on the other hand, see plants such as autumn olive, Japanese honeysuckle, multiflora rose, oriental bittersweet and garlic mustard as a huge problem in the 4,000-acre park and are eager to weed them out. The Illinois Department of Natural Resources commissioned a survey that began in late 2004 to find out how Giant City visitors might respond to a more aggressive management plan.

In conjunction with that project, Davenport also oversaw a study conducted by master's student Molly Braddock of Anna using focus groups to get a handle on what the region's residents think about nature in general, invasive plants in particular and efforts to control them.

"That combination gave us both breadth and depth (as to likely public attitudes toward management options)," Davenport said.

The visitor survey, conducted by graduate student Melissa L. Baker of South Fulton, Tenn., tabulated responses to a lengthy questionnaire by 266 visitors chosen at random from the park's visitor center, campgrounds, trailheads and parking lots.

"It was designed to be representative of the visitor base," Davenport said.

The focus group study consisted of sessions with people likely to have an interest in the management of plants, shrubs and trees— regional volunteers, community leaders, environmental activists and individual nursery operators.

"We thought it would be better talking with business owners one on one than in a focus group setting," Davenport said.

"Business owners who are in competition with each other may be less candid about their business practices."

Like the visitors, folks in all groups saw non-native, invasive plants as a threat to the region's scenic beauty and species diversity. Yet, when shown a picture of garlic mustard, a non-native, invasive plant, more than 80 percent could not identify it. Furthermore, their cumulative assessment of garlic mustard on a seven-point "pleasantness" scale (with seven being the most pleasing) came in at 4.6.

"Garlic mustard is a delicate-looking plant, and the flowering stage is pretty," Davenport said. "Everybody recognized crabgrass, though, and they all hated it!"

The group response to garlic mustard demonstrates one of the problems with trying to control the spread of non-native plants. They often look pretty or smell good or provide food for wildlife or control erosion or shelter both people and critters from the wind.

"There are so many human-centered values and utilitarian reasons to enjoy different types of vegetation, regardless of whether they're native or not," Davenport said.

"However, ecologically speaking, non-native plants have caused a great deal of damage, including reducing biodiversity worldwide."

The good news is that both visitors and group participants found a fairly high degree of management acceptable. In the park, an approach that combined such methods as increasing native plant numbers and removing non-natives by hand or with fire won the most widespread visitor support.

"We were surprised that people were relatively in favor of prescribed burns, as fire in general is such a high-profile and controversial issue," Davenport said.

"We were encouraged to learn people weren't adamantly opposed. Respondents generally understood there's a need for controlled burning. That's sort of a new perspective."

Among the focus groups, mechanical and cultural control plus prescribed burns were the top choices for controlling invasive plants, whether participants were talking about residential areas, public lands or farm fields. Chemical control ranked near the bottom across the groups for all three types of land.

Davenport sees the region as ripe for the kind of education that would focus not only on its natural beauties but on the problems associated with its "unnatural" ones, too.

"I think it's important to talk about what threatens the park (and other areas)," she said.

"Something may be nice and green and lush, but think about how it affects other things. Native wildlife, for example, generally depends on native plants."

Because people clearly don't know what the invaders look like, Davenport is encouraging Giant City managers to develop a controlled demonstration area where folks could see these plants up close and perhaps even get ideas for getting rid of them. Perhaps they could pull community members in as weed pullers or as "scouts" for invaders or as free-time experts and guides to the park's overall flora.

"What people value about Southern Illinois, whether it's the park or the countryside, is the scenic quality," Davenport said.

"The seasonal changes and diversity in vegetation are really important to people. We need to build on that."