As her feet crunched the dirt path of Lone Lake Park in Minnetonka on a recent afternoon, Heather Holm inspected the surrounding wildflowers for a glimpse of the rusty patched bumblebee.

The pollinator expert first spotted the bee in the park in summer 2016. The U.S. Fish and Wildlife Service listed it as an endangered species less than a year later.

Now a proposal to build almost 5 miles of mountain biking trails across the wooded slopes of the park has Holm looking again. She and other environmentalists are worried the trails could affect the bee’s habitat, potentially disturbing the already sensitive species.

Holm and Minnetonka resident Maureen Hackett have petitioned the state’s environmental quality board to conduct an environmental review of the trail project. The City Council is scheduled to act Monday on their request.

The real concern, Holm said, is that the bike trails would be “bisecting and chopping up a lot of habitat and potential places where the bee could be nesting.”

Mountain or off-road biking has boomed in popularity in recent years, with domestic mountain bike sales rising to $577.5 million in 2017, according to the NPD Group, a market research company. It’s swept into school districts such as Minnetonka and Hopkins, which have formed their own mountain bike racing teams.

The sport’s growth has led residents to ask whether trails might be built in local parks, said Matt Andrews, the executive director of Minnesota Off-Road Cyclists (MORC), a nonprofit that maintains trails across the state.

The Twin Cities area now has more than 85 miles of off-road trails, up from 10 miles in the late 1990s, according to officials.

“Mountain biking is now a pretty mainstream, legitimized recreation opportunity,” Andrews said. “Ten, 20 years ago, we used to beg for any piece of land that we could get.”

Hungry for local trails, Minnetonka residents pleaded for the city to build some. The park board selected Lone Lake Park, a 146-acre preserve with wetlands, dense woodlands and sunny prairies near Shady Oak Beach, as a potential site for the trails. Estimated cost of the project was set at $188,000.

The city commissioned a study of how trails would affect the environment, including the rusty patched bumblebee and the northern long-eared bat, a threatened species found in the park.

The conclusion: While it was unlikely the two species would be lost, trails increased the risk that the bees and bats would be “disturbed and potentially displaced.”

Holm, who has devoted much of her life to preserving native species, was disappointed with the study. She said it was too short and flawed because it was done when snow was still on the ground.

“They greatly missed what this looks like with the number of flowering plants on the slopes,” she said. “They drew many conclusions that were incorrect about impacts to the bumblebee.”

Overall, she and Hackett are concerned mountain biking would destroy vegetation, spread invasive species, erode the soil and increase noise, disturbing not only wildlife but also the visitors who enjoy the park’s tranquillity.

“The addition of mountain biking will fundamentally change the character of the park,” their petition reads.

Although the study acknowledges the project would have an environmental impact, the city could work to minimize it, according to Recreation Services Director Kelly O’Dea.

“I think you would expect with a sustainably built trail that we could hopefully mitigate many of the environmental concerns that are out there,” he said.

A controversial project

Minnetonka has worked hard to restore its parks over the last two decades, ever since a study found that most of its natural spaces were seriously deteriorated. With help from volunteers, including Holm, the city removed invasive species in several parks and improved habitat for native plants, insects and predators such as foxes and coyotes.

Recreational projects in Lone Lake Park, such as the mountain bike trails and pickleball courts currently under construction, have the potential to undo much of that progress, Holm said. The rusty patched bumblebee, whose population has declined by more than 87 percent in the last 20 years according to federal officials, is just one of the species that could be at risk, she said.

Little is known about the bee’s presence in Lone Lake Park. While Holm has spotted worker bees along the walking trails during the summer, she suspects the queens start their lives in the wooded slopes where the trails would go. By performing an environmental review, the city would learn more about their nesting sites, she said.

All sides agree the trail project has been surprisingly controversial.

“Typically we do not experience this sort of opposition,” said Andrews, whose cycling group has offered to advise the city and would likely help with trail upkeep.

Lone Lake Park “looks like an ideal sort of setting for mountain bike trails,” Andrews said, adding that though the trails may look wide and bare once they’re carved out, vegetation would grow around them over time.

“Any sort of change or any implementation of a recreational opportunity is going to have some impact,” he said. “You’re going to have to give up some sort of footprint … to make it usable for whatever sport you’re going after.”

Back at the park, Holm continued to look for the bee with the fuzzy red-orange patch. Bees and butterflies flitted around the trail vegetation as the sun beat down. Holm pointed at a black and gold bumblebee hovering over one flower and a half-black bumblebee over another.

Hackett, who walked alongside Holm, said Lone Lake is her favorite park in Minnetonka. “You don’t even feel like you’re in Minnesota in some parts of this park,” she said.

Holm said she worried that a council rejection of the petition on Monday could lead other cities to overlook endangered species in their own parks or natural areas.

“If they disregard an endangered species as present and there is no protocol … it really does set a bad precedent,” she said.