April Reese, E&E reporter
Published: Friday, November 2, 2012
Among the devastating impacts of Hurricane Sandy, the superstorm uprooted thousands of trees, setting back efforts to expand the urban forest in several East Coast cities.
Many cities slammed by the storm lost several hundred trees each. The felled trees not only caused several deaths and massive damage to property and power lines, they also left gaping holes in the tree canopy, unraveling years of restoration work.
Baltimore, for instance, lost 500 trees, including an Osage orange tree in Druid Hill Park that had been designated a "notable tree" by the city. Washington, D.C., lost about 224 of its 140,000 trees, according to the city's Department of Transportation, which oversees the Urban Forestry Administration. The largest tree to fall in the district was about 12 feet in diameter.
In New Haven, Conn., high winds knocked down a 103-year-old oak tree and exposed skeletal remains from the 19th century, officials said Wednesday. The tree had been planted in 1909 in honor of the 100th anniversary of President Lincoln's birth.
Official tree loss tallies are not yet available for Boston and New York City, where city foresters and maintenance crews continue to work long hours removing downed trees.
"We're currently assessing damage to the street trees," said Zachary Feder, a spokesman for the New York City Department of Parks and Recreation. "We haven't been able to count all the trees in the wooded areas. The first priority is to clear the trees from the streets."
As officials continue to tackle the immediate problems associated with fallen trees, assessments of the impacts to the tree canopy and urban forest restoration efforts have just begun.
"It sets us back," said Erik Dihle, Baltimore's city arborist, in an email. The city will have planted almost 9,000 trees by the end of the year as part of its efforts to expand its tree canopy to 40 percent by 2040, so the city will still see a net gain in trees in 2012, but those trees will take many years to mature, he added.
Boston, which aims to expand its tree canopy from 29 percent to 35 percent by planting 100,000 trees by 2020, also is expected to have to make up for the losses from the storm.
Trees in full leaf-out more effectively block high winds -- up to a certain point -- and actually can help protect buildings during storms. But this time of the year, when many species of trees have lost most of their leaves, more wind can pass through, said David Nowak, project leader for the Forest Service's urban forest, environmental quality and human health office in Syracuse, N.Y.
"When the trees dropped the leaves, they're acting as less of a force to block the wind," he said. "This is just a theory, but a tree is an object, they take the brunt of the wind, and if there's too much wind, they topple over."
John Thomas, associate director of Washington, D.C.'s Urban Forestry Administration, added: "At this stage, the wind is able to move around and through the tree, because there aren't leaves to block it. A lot of that wind kept going through the canopy. That makes a big difference in what they're able to withstand. It's like a building that's finished versus a building that's not yet been completely built."
Last summer's derecho that hit the Washington, D.C., area caused more tree damage than Sandy did, he added. While the hurricane was less intense in D.C. than expected, somewhat windy conditions prior to the storm may have also helped lessen the damage, he said.
"I think the [storm] winds are less impactful under those conditions because there's already 10-40 mph winds, the trees are already bending," Thomas said. "When we had the derecho [in June], the trees were just sitting, and then the high winds came through. So they had to go from zero to 70. That's my personal theory."
D.C. had already planned to plant about 1,500 trees this fall under its tree planting program, part of the city's effort to expand the urban canopy to 40 percent from the current 36 percent, and some of those new trees will fill the holes left behind by the storm, he added.
Some residents, however, are a little reluctant to see new trees go in, particularly if their cars or houses were damaged by the ones they are replacing.
"We're going to have to put a lot more effort into educating people," Thomas said.
Trees provide a whole host of ecological and aesthetic benefits to the city, he added. Urban trees capture rainfall, reducing stormwater runoff -- a major conduit for pollutants entering the Chesapeake Bay -- and shade buildings, cutting air conditioning costs. They also provide habitat for birds and other urban wildlife.
"Overall, trees provide so much more environmental benefit that it outweighs the risk" of tree falls during storms, Thomas said.
The gaps left behind from the trees felled by the storm provide an opportunity to avoid the tree-planting mistakes of the past, which contributed to the damage toll, added Bill Toomey, director of forest health protection for the Nature Conservancy, who lives in Newtown, Conn., about 60 miles northeast of New York City and one of the towns that remains without power.
"There's an opportunity to do something that's been talked about for a long time, and that is to make sure we put trees in the right place," he said. "Unfortunately, a lot of times in the past, the trees planted near power lines were way too big for that location."
The storm also offers a lesson in the importance of properly maintaining urban trees, Toomey added. During the recession, many cities scaled back tree maintenance budgets, leaving trees more vulnerable to high winds.
"Even a healthy tree can come down in conditions like that with 70- to 80-mile-per-hour winds, but some trees probably could have used a little more pruning and maintenance," he said. "This is a case where a little prevention can really add up in the long term. The money required to maintain trees near power lines is minimal compared to the costs we're seeing from damage from the storm."
Reese writes from Santa Fe, N.M.
The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. The Conservancy and its more than 1 million members have protected nearly 120 million acres worldwide. Visit The Nature Conservancy on the Web at www.nature.org.