Urban Stress Kills Canyon's Cottonwoods

Tens of thousands of raw-footed hikers who've trudged into the Grand Canyon to Phantom Ranch know what a relief it is to finally collapse in the shade of the famous campground's giant cottonwood trees.

Until last fall, though, no one realized that the trees themselves could use a little relief.

Two tree experts say the Phantom Ranch cottonwoods suffer from many of the same urban stresses that kill trees in, say, downtown Pittsburgh. Arborist Dudley Marburger and University of Arizona professor Bill Miller were called in last fall by National Park Service rangers who had noticed that the trees looked diseased.

Since then, Marburger has had to remove about thirty of the 300 or so cottonwoods, and he fears that unless the park service acts fast, many more of the trees will die within three to five years. Marburger accuses the park service of not taking enough steps to save the trees, but the park service says some of Marburger's suggestions are just too expensive.

In the 1930s, when the Park Service sent the Civilian Conservation Corps down to Phantom Ranch to plant baby cottonwoods, the federal government was merely looking for a way to employ down-and-out Arizonans and at the same time make the bottom of the Grand Canyon National Park more hospitable.

The trees, being cottonwoods, grew quickly. And for decades, they appeared to be healthy and happy.

But then Phantom Ranch got crowded. The park service estimates that from 100 to 300 tourists now troop into the area daily. Such a tourist glut is bad news for the cottonwoods.

So many people tromp around the trees that they slowly suffocate and starve the cottonwoods, says Marburger. They pack the dirt down so tight that no oxygen and nutrients can reach the roots. This "urban stress" causes the upper limbs of many trees to die, says Marburger, and then bugs, birds and bacteria infest the trees.

So the park service, fearing the trees might keel over on a tourist, called in Marburger and Miller. "They were afraid of liability problems," says Marburger. "So we went in for six weeks last fall and took out dead trees and cut out the dead branches." Marburger says he pruned off tons of dead wood, making the trees temporarily safe.

Marburger went a step further, though. In a report he later delivered to the park service, he offered a slew of recommendations aimed at saving the cottonwoods from further "people pressure." His suggestions included redesigning the campgrounds and trails; watering the trees with effluent from Phantom Ranch's sewage treatment plant; fertilizing the trees; replacing sixty-year-old irrigation ditches with a modern drip-watering system; improving trails by mulching them with wood chips made out of the very branches Marburger pruned last fall; punching holes in the ground to enable air get to the roots.

The park service cooperated--up to a point--says Jim Hutton, the agency's Phantom-area ranger. Hutton figures the feds have already spent about $10,000 trying to save the trees, and he contends they're probably nearing the end of their natural life spans anyway. (No one seems to know the life span of cottonwoods.)

Hutton points out that the trees are not only pruned to perfection now but also receive hearty doses of vitamins four times a year. What's more, he says, trails have been modified slightly so that hikers aren't as close to the trees. And new trees have been planted to take the place of those removed.

But Hutton says the park service probably won't add a drip-irrigation system or cart a machine down from the top of the canyon so that mulch can be made of last year's prunings. All of this irks Marburger. "Trees don't care about budgets," he says. "They die if they aren't cared for."

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Terry Greene

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