Peak baggers prepare to shell out: The trails you love to climb to 14,000-foot summits will cost $24 million to build or replace.

That’s the upshot of a new report by Colorado Fourteeners Initiative, a Denver-based nonprofit that spent three years evaluating trails on 14,000-foot peaks for sustainability and gauging their impact on fragile alpine habitats before assigning each a letter grade based on time, money and logistics involved in bringing them up to standard.

Colorado’s finest: Photos of the state’s 54 fourteeners

The report card issued Tuesday suggested that heavy use is hastening erosion and disrupting habitats on a number of peaks, including Grays and Torreys Peaks near Denver, which earned a D, and Mount Bierstadt near Denver, which earned an F.

Thirty-nine of Colorado’s at least 54 14er peaks were included.

The remaining mountains, including Pikes Peak, couldn’t be evaluated because ongoing projects or other reasons, according to the report card. CFI said it will assess most of them later, assuming funds become available.

The $24 million price tag is tied to the challenges inherent in constructing trails on 14ers, which include difficulties in transporting materials, constant weather interruptions and a limited season during which it is safe to work, the group said.

Despite the harsh marks and eye-popping trails tab, Lloyd Athearn, the group’s executive director, said he’s “optimistic” about the future of Colorado’s 14ers.

“These are the crown jewels, the iconic backdrop, of Colorado, and a lot of people understand that,” he said Tuesday.

While cash-strapped federal agencies, including the Forest Service, are spread too thin to provide the funds, those who love the mountains may step up with private-public partnerships, Athearn said.

He said the cost of building and maintaining the trails pales in comparison to the economic benefits they generate, a message he called quick to register with the businesses, local governments, philanthropic groups and individual donors who have supported previous projects.

“If properly motivated, they’ll help us make it happen – maybe not by the end of the season, but it’s definitely achievable,” Athearn said.

Part of the nonprofit’s mission is to keep the peaks open and accessible, which Athearn argued can be accomplished by building durable, sustainable trails that blunt the impact of hikers and resist erosion by shedding water from relatively mild grades.

The report bears out the idea that smart trail construction, though costly to install, could save money in the long run, Athearn said.

In all, 24 trails that were planned by the Forest Service and built by Colorado Fouteeners Initiative or similar nonprofit would cost $6 million to restore or improve.

By contrast, 14 user-created routes – so-called “social trails” that sprout up over time through the accumulation of visitors – would cost $18 million to replace with sustainable routes.

Social trails generally carve the shortest distance to the summit, resulting in steepness that contributes to erosion. Such trails become widened and braided through dispersed use, magnifying the strain on fragile alpine turf.

Eight of the nine trails that earned an “F” were unplanned routes, the report shows.

Only two trails earned a perfect grade: Those to Blanca Peak and Ellingwood Point near Alamosa and the one to North Maroon Peak near Aspen.

The trail to Blanca Peak and Ellingwood Point was built by volunteers working with the Rocky Mountain Field Institute (RMFI) of Colorado Springs, which has constructed trails to at least five more 14ers in the Sangre de Cristo range and is midway through a multi-year project to build a trail to Kit Carson and Challenger Point.

“It’s an area we’ve been working in a long time,” said Jennifer Peterson, executive director of RMFI.

She said much of the public wasn’t aware of groups like RMFI and CFI, who partner with federal agencies to marshal volunteer trail builders.

But the work, she said, is only possible with the public’s support.

“Slowly, we’re trying to get that message out.”