NYC’s Decennial Street Tree Census Will Enter the Digital Age This Year

No one would mistake New York City for an arboreal haven. There’s a reason New Yorkers drive to Vermont in the fall.

Nevertheless, lining the streets of this city are 592,130 trees, representing 168 species: from London planes to ginkgo biloba to callery pear. Brooklyn has about 150,000 trees — about three times as many as Manhattan. Queens has everybody beat, with upwards of 250,000, more than any other borough.

How do we have so much detailed information about New York’s leafy amenities? It’s all thanks to the decennial (that’s once every ten years, folks) Tree Census, when teams of counters descend on the city, tallying every street tree in the five boroughs. It’s a huge effort, requiring thousands of volunteers.

It’s also thanks to the tree census — which begins on May 19 — that we know exactly what species each one of those trees is. And their diameter. And exactly where they’re located. (Well, almost exactly. But more on that in a minute.)

Since its inception in 1995, the street tree census has made the city’s “urban forest” something that could be managed like any other resource. Prior to that, the city’s parks department was flying somewhat blind. They knew there were plenty of trees, but the complexity of the picture wasn’t so clear.

“Nineteen ninety-five was the first time we really knew how many street trees we had citywide,” says Jacqueline Lu, director of geographic information systems and analytics at the New York City Department of Parks and Recreation. That first census was a critical step to better management, she says. “In the same way that the Department of Transportation resurfaces city streets on a rotation, we were able, for the first time, to say what a tree-pruning rotation would look like.”

Back then, the process was decidedly analog, involving actual pens and paper, and relied on the city’s street address grid for mapping tree locations. The process hadn’t changed much by 2005, the last time the census was done.

But a lot will change this year, Lu says. Brand-new for 2015 is a tablet- and smartphone-based tallying system that will make the job not only faster and less labor-intensive, but also more accurate.

Called TreeKIT, the custom app allows volunteers to combine old-school technology — a measurement wheel, the kind of thing you may have seen surveyors use — with GPS capability to accurately map a tree’s exact location. Back when the mapping was based on addresses, locations were often imprecise. And since trees can often look somewhat alike, that created some confusion.

The job of census taker is pretty simple, Lu says: Sign up with a partner or a group — it’s free — select a time slot, and you’ll be given a brief training presentation. Voluntreers (get it?) will be issued a tablet and a measuring wheel, along with a census tract to cover. It’s a pretty low-impact, enjoyable way to spend a day, Lu adds.

Over the years, the data have revealed much about the city’s street tree stock, such as the somewhat disproportionate representation of one species — the London planetree — which accounted for over 15 percent of the total at last count.

Why so many, you ask? Are they particularly well suited to the city? Not so much, Lu says. Actually, there’s a pretty simple explanation; Robert Moses loved London planetrees.

Moses, the city’s Machiavellian public-works don, controlled virtually all construction and development in the city for half a century. And what Moses wanted, Moses got. Which means, in this case, a buttload of London planes.

“We don’t plant a lot of London planetrees anymore,” Lu admits, because it’s not good to have any one species over-represented. After realizing two censuses ago that Moses had London-planed New York to death, the parks department has been trying to branch out, if you will. But the city is still pretty well focused on a few species. Just ten varieties account for 74 percent of the total tree count.

A detailed breakdown of the numbers can be found here, but most of the city’s trees are selected for hardiness. New York isn’t an easy place for anyone, or any plant, to survive.

Ginkgos, with their waxy, fan-shaped leaves, make up about 3 percent of the total, but they’re popular for very specific reasons. They’re able to thrive in areas where their roots have little room to expand, often the case for street trees. And they’re extremely resistant to pests. (Actually, they’re extremely resistant to just about everything; a handful of ginkgo trees famously survived the U.S. bombing of Hiroshima during World War II, which killed as many as 100,000 people.) Callery pear, another of the city’s most common species — about 10 percent of the total — have similar resilience.

Both species also smell awful at various times of the year. Ginkgo seeds smell roughly like vomit, flowering callery pears like — and there’s no polite way to put this — semen. Yep, semen.

Once the tree census wraps up later this summer, all of that data will be crunched and released to the public. And if the past is any guide, people will find out some cool ways to use it.

Web designer Jill Hubley created the color-coded map below that shows the city’s street tree population by species and diameter. You can check out the interactive version at her website, here.

While most of the trees counted in 2005 will, presumably, be roughly where the parks department left them, Lu says there are some unknowns. A lot has happened over the past decade.

“There’s been a Hurricane Sandy,” Lu says. “There have been a couple of tornadoes. We’re excited, because we know this data is going to help set the direction for how we manage our urban forest going forward. We don’t know what we’re going to find.”