When it comes to protecting or saving trees at construction sites, most developers and construction companies view arborists as tree-hugging obstructionists, says Chris Cowles, an arborist and urban forester currently working on the Great Excavations project on the Homewood campus.

"Some people think I work for the government," Cowles says. "They say, 'Oh, you're here to inspect the trees.'"

Chris Cowles

Even people who want to do the right thing often fail to consider what effect construction will have on the trees, Cowles says. And construction damage to trees can appear three or four years down the line.

"Traditionally, arborists have been brought in as a mop-up after people realize, 'Uh, gee, we think our trees are damaged,'" Cowles says. "'Can something be done to make sure they're still alive? They're starting to turn yellow, what do we do?' And that's a bane of arborculture because the damage is already done."

But the Hopkins project can be counted among the happy exceptions, when arborists are brought in early and work hand in hand with designers and the various construction trades to make sure every effort is being made to save and protect as many trees as possible.

Cowles, a consulting urban forester for the Care of Trees, a nationally recognized tree company headquartered in Chicago with regional offices in Gaithersburg, Md., has been involved since March, reviewing plans, inspecting and cataloging the roughly 180 trees that are being impacted and following through with on-site actions to protect the trees.

"He's very good at what he does," says Michael Vergason, of Michael Vergason Landscape Architects, Arlington, Va., the lead landscape firm on the project. "We try to look at everything, but it's wonderful having another person who is really good at reading drawings. He's always looking at all utility routings, pathways, anything that has an impact on trees, and advising us on ways to avoid a problem or mitigate it."

Even before construction began, Cowles and his crew were busy putting up protective orange fencing around areas that are thick with tree roots, the "lungs" of trees, which are often severely damaged by construction if precautions are not taken.

Among the trees that Cowles is suggesting should be cut down are five extremely tall tulip poplars just to the east of Homewood House that were damaged by earlier construction. These trees, at least 100 years old, were part of the "native forest," Cowles says, "planted by squirrels, not by humans."

Sometime in the last 50 years, Cowles says, construction at or near the tall trees damaged their roots, setting in motion a process that caused the insides of the trees to rot, making them hollow and fragile. Their branches, which are high up, are dead and broken, he says. In high winds, the trees might topple.

"Not only could they fall on the Homewood House, but people walk under them," Cowles says.

But most of the trees affected by construction will be saved; only about 40 are slated to be relocated or removed. Those marked with blue ribbons will stay, orange ribbons will be removed, and blue and white ribbons will be relocated.

Already, the crews have taken down a handful of trees and replanted many more. Two cut-leaf Japanese red maples were relocated from in front of Shriver to in front of the Milton S. Eisenhower Library, and a number of saucer magnolias were transplanted from the lower quad to the entrance gate on Wyman Park Drive.

"The landscape architects are very much into preserving trees," says Cowles, who meets weekly with the design team and regularly with the construction crews and various trades. "We've been moving lighting fixtures away from trees to give them more room, shifting proposed walkways farther away from trees."

Much of the work involves striking a balance between what construction crews require and protecting the precious root systems of the trees. "Tree roots in a way function as our lungs do, [in] that they take oxygen and they also give off poisonous gases in the biological process," Cowles says. "If you just fill over a root system, that can shut off that air-gas exchange, and [the trees] can actually suffocate."

Cowles, a graduate of the University of Florida and a certified arborist, brings more than 20 years of experience to the job and a soft wisdom that helps him work well with construction crews.

"We take care of a lot of issues and conflicts in the design phase, and that makes construction a lot easier," Cowles says. "We tell the contractors, 'Don't worry, we're not here trying to tell you, Whoa, stop your yellow machinery while we go back and figure out what we're going to do with this tree.'

"A lot of times, it's 75 to 80 percent people skills, relationships," Cowles says of his work. "So when I'm on a job site, I spend a lot of my time going around to the different foremen in the different trades. 'Hey, how you doing? Is any of the fencing in your way? Are some of the trees or branches in your way? Do you have enough room to work?'"

Technology plays a role, as Cowles and his crew employ the latest tools and methods for protecting trees. Despite a popular belief that roots extend deep into the ground, in most soils they go no deeper than 24 inches and can spread far beyond the tree's canopy of leaves.

A lot of the work going on this summer involves ripping up asphalt pathways and repaving with brick. In some areas, if construction proceeded normally, workers would dig down 12 to 18 inches and basically rip through the underlying root system, says Cowles.

So in several areas, instead of digging down, they're building up, employing textile rugs and aeration mats to form a strong but breathable base on which to put the brick pavers. This technique is allowing them to save a stand of willow oaks between Homewood House and the MSE Library, he says.

Another important tool is the air spade, which blasts air into soil at Mach 2, or 1,400 miles per hour, allowing arborists to expose roots without damaging them.

Already, Cowles and his crew have used the air spade several times to examine roots to determine the health of a tree and to plan ways to help it thrive in the long run. For instance, they recently blasted away crushed fill near an old walnut tree on the upper quad, revealing thick roots running through soil so compacted, it's as hard as concrete.

Before the new pathways are put down, Cowles says they will treat the hard-packed soil with a product composed of kelp and yucca, which will help loosen the soil and make it easier for roots there to absorb moisture and exchange gases.

In addition, the Care of Trees staff have been treating a number of trees with fertilizer and a beneficial fungus called mycorrhyzal, which adheres to the roots and increases their absorption rate by up to 400 percent.

Cowles and Care of Trees have won awards for their tree-saving efforts and have done work on a number of other college campuses. They have done larger projects, but none more intense.

"One day we're doing the design, the next day we're doing the construction," he says. "It's hard to keep up. It's like nine projects rolled up into one."