It sounds like a no-brainer - a bike trail alongside a world-famous scenic highway through two of Canada's best-loved national parks.

But Parks Canada documents show the proposed trail down the Icefields Parkway between Banff and Jasper raises a host of complications, from damage to wildlife habitat to safety concerns and increased development pressure.

“It might sound like an innocent trail, but it also comes with other considerations,” said Alison Ronson of the Canadian Parks and Wilderness Society, which has opposed the current proposal.

The most recent federal budget contained $66 million to develop a 107-kilometre bike trail from the Jasper townsite to the Columbia Icefields along the parkway. The trail could eventually extend all the way to Banff.

Cyclists currently hug a narrow shoulder along the highway. Parks Canada is proposing a separate, paved route buffered from the busy road by 10 to 20 metres of trees.

Parks Canada is conducting public consultations and developing an environmental impact assessment. No decisions have been made, said spokeswoman Audrey Champagne.

“A detailed impact analysis will be undertaken to ensure that Parks Canada has a clear understanding of the potential environmental impacts of the project and can address any risks or adverse consequences,” she said in an email.

Environmental groups have expressed concerns. Documents obtained under freedom-of-information legislation by researcher Ken Rubin and provided to The Canadian Press suggest Parks Canada officials have some of the same qualms.

“Trail use is likely to be high and will induce further development ... or at least demands for further development,” reads a 2016 background document.

Pullouts and rest stops may need to be built every five to 10 kilometres. The trail would also have to be connected to campgrounds and other infrastructure with more asphalt. Those pressures are not considered in the current plans or environmental assessments, the document says.

The trail would lead through critical habitat for bats, olive-sided flycatchers and two species at risk - the mountain caribou and the whitebark pine. Champagne said the trail would be aligned to prevent disturbance to the pines.

Wetlands along the trail are “insufficiently mapped,” the documents say. A salt lick for mountain goats would have to be considered.

Pavement would run through up to nine kilometres of wilderness.

“The concept was developed based on the principle of utilizing the already disturbed right of way and the old road along the Icefields Parkway, while at the same time designing a route that enhances public safety,” Champagne said.

The trail could also create encounters between cyclists and grizzly bears. Grizzlies are drawn to berries that grow where trees have been cleared, the document notes, and cyclists are less likely to carry bear spray. They also travel quietly at much higher speeds than hikers.

“Some mitigation measures could have relatively significant costs which should be factored into decision-making,” the documents say.

The documents show Parks Canada is wary of public concern.

“Call it (a) bike lane, not trail,” says one. “'Trail' is setting off amber flags for a number of constituents.”

The agency has previously said it is trying to find ways to widen its appeal beyond traditional visitors.

Parks Canada management plans include expanding cycling opportunities. Ronson suggested that could be done by expanding the shoulder of the current highway. The documents say that would be difficult to engineer, given the terrain.

Ronson's group has calculated the amount of paving needed for a trail along the entire highway at the equivalent of 116 football fields.

The total budget for the project is about $86 million, with about $20 million coming from Parks Canada's capital budget. Champagne said that won't affect the agency's ability to preserve and protect the region.

Ronson said that money would be better spent on Parks Canada's primary job.

“Over the last few years, their budget has been cut so much that we don't see enough interpretation or education now,” she said.

“This is really egregious when you consider the cuts to the science and conservation programs in the park.”