Clive has begun removing more than 400 trees along its scenic Greenbelt Trail as it prepares to straighten the trail to cut down on the number of blind curves.

The city says the changes are needed to improve safety for trail users and to protect against erosion and flooding from nearby Walnut Creek.

But some trail users worry the changes will irreparably damage the path's chief features: its twists and turns, and the overhead canopy of mature trees.

"It's the most beautiful trail I’ve ever seen," said Chris Wolf, a Des Moines resident who walks the greenbelt trail every day as part of his dog-walking business. "Cutting down 400 trees is egregious. Once the big trees are down, they're down. They're not coming back."

Clive is concentrating on a half-mile stretch of the trail from Northwest 114th Street to the Porter Shelter in Greenbelt Park. The trail will be straightened and moved away from Walnut Creek.

The project is the first on a long list of changes outlined in a 25-year, $41 million master plan for the entire greenbelt system.

This segment of trail was identified as having the most immediate need because it's where Walnut Creek flows the fastest, said Assistant City Manager Matt McQuillen.

"If we don't do something it will eventually erode the trail away," he said.

The trail will move a few feet north of its existing paths, placing it at least 60 feet from the creek. This will allow Walnut Creek to naturally meander and give the city room to complete bank stabilization improvements, he said.

Two oxbow lakes will be restored as part of the improvements. The lakes will help slow Walnut Creek water flow during heavy rains by giving the creek places to naturally pool.

McQuillen said the blind curves and speeding cyclists have become a safety issue on the heavily used trail. The city will replace sharp turns with "long, slow curves" and widen the path, McQuillen said.

Scott Sumpter, founder of Bike Iowa, said the improvements will benefit cyclists and commuters.

The Greenbelt Trail is a link between downtown Des Moines trails and the Raccoon River Valley Trail in Waukee, he said.

"I think the new trail will be good for cyclists, but it may not be as scenic for residents," he said. "Those corners get wet and mossy so there's quite a few accidents there."

Sumpter said he's crashed taking a corner on his way to work and has seen others do the same.

To accomplish the straightening project, the city needs to remove hundreds of trees.

Officials estimate about 438 trees will be cleared. That may change if the city identifies trees it wants to save by adjusting the trail's path, McQuillen said.

About 20 of those trees are more than 24 inches in diameter, but the majority are less than 15 inches in diameter, he said. The city plans to reforest the area once the project is complete, though officials won't have an exact number of new trees until they see what's taken out, he said.

Emma Hanigan, urban forestry coordinator for the Iowa Department of Natural Resources, said the reasons behind the project make sense, but she wonders whether the city's tree replacement plan is adequate to restore what canopy is lost.

It's especially important at a time when the state's tree canopy is declining, she said. Iowa lost 97,000 acres of woodlands from 2009 to 2013, according to a U.S. Department of Agriculture Forest Service report released last year. It's the first time in 40 years that the state has seen a net loss in forested land and more is expected as the emerald ash borer spreads and kills off urban trees.

"We want to see those numbers be pretty similar in size so we're not losing all those benefits that we already had," Hanigan said. "We encourage every community to replace every tree they remove, and plant even more, because we're losing trees and we're losing ground, as far as the canopy cover goes."

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Portions of the trail are closed while the trees are being removed. Detours will be posted while the city works to restore the oxbow lakes. That project should be complete by winter.

The trail realignment will take place next summer.

A second phase of changes between the Porter Shelter and Northwest 100th Street will occur in a few years. McQuillen said the trail's alignment won't change as much as the first phase, so fewer trees will have to be removed.