ROBERT SIEGEL, HOST:
Now to New York City, where Hurricane Sandy and the nor'easter that followed it took down almost 10,000 trees in New York City. That is far more than any other storm in the city, at least storms in which tree damage was recorded.
NPR's Margot Adler has the story.
(SOUNDBITE OF CHAIN SAWS)
MARGOT ADLER, BYLINE: You can hear the sound of chain saws all through Central Park, where I'm walking with Ken Chaya, who knows more about the park's trees than just about anybody else. He's created a map that charts every single tree in the Park, about 20,000. During the two storms, some 800 trees went down here. Chaya shows me some of the damage, as we look over a stone arch, down into the still closed North Woods.
KEN CHAYA: And looking over Glen Span, I can count 1-2-3-4-5, at least five fresh cuts of mature trees. There are tree crews in here.
(SOUNDBITE OF A CHAIN SAW)
ADLER: Like the one we are hearing?
CHAYA: Like the one we are hearing.
ADLER: Five days before Sandy, the city's Parks Department was already making arrangements with tree crews from around the country. They'd noticed that weather was changing - two tornados, a freak storm they called a microburst that took down 500 trees in this park, an unusual early winter storm, Tropical Storm Irene, all in the space of two years.
Bram Gunther is chief of forestry, horticulture and natural resources for the city's parks department.
BRAM GUNTHER: When that happened, that really opened our eyes and it opened our eyes to the power of these storms, which we had not experienced directly in New York City - at least since I was a child.
ADLER: Irene took down some 3,400 trees, Sandy, three times that amount. And the downed trees were big trees - old trees, often beloved trees.
GUNTHER: The bigger the tree, the more carbon it captures, the more particulate matter it filters, the more storm water it captures. So it's a huge number in terms of environmental benefits and what it does for a community.
ADLER: The day after the storm, they had people walking, riding, bicycling, every New York City block with hand held computers assessing damage and putting in work orders - 33,000 blocks.
GUNTHER: We do every single one to assess and evaluate the damage of the trees and the safety of that particular block.
ADLER: Gunther could monitor all these computers from his storm mobile command center.
(SOUNDBITE OF A CHAIN SAW)
ADLER: Back in Central Park, Ken Chaya points to a 75-year-old black locust.
CHAYA: Its trunk was just yanked out of the ground by the wind. And it was leaning over this path. It had to be cut. And we hear saws going.
ADLER: We step over a fence into the North Woods - where we shouldn't really be without hard hats - for just a moment, to look at the massive stump of a Northern Red Oak. The center was rotted out and Chaya, who is six feet tall, lies on the diameter; he fits perfectly. Nearby a downed tree pulled up rock, a piece of Manhattan schist, the 450 million-year-old bedrock that lies beneath Manhattan.
Chaya says there is only a little layer of soil over the bedrock and trees can't sink a deep tap root, so they branch out horizontally. And in a storm...
CHAYA: Many trees like that just topple over. Their roots are not deep enough
ADLER: The city is committed to planting a million trees by 2017 and it's ahead of schedule. But remember, newly planted trees are small. It will be years before they can truly be what Chaya calls urban forest.
CHAYA: Our urban forest, it's fading. We're losing it.
ADLER: And if you think, ah, it's just trees, a USDA study said New York City has more than 5 million trees. They remove 42,000 tons of carbon per year, and about 2,000 tons of air pollution. And the study even put a monetary value on what those trees do: $5.2 billion.
Margot Adler, NPR News, New York.