Every ten years since 1995, hundreds of New Yorkers leave their homes armed with tape measures and survey wheels to identify, measure, and record every single street tree in New York City. In 2015, more than 2000 volunteers participated and completed a third of the census, saving the city $100,000. The whole process takes two seasons and thousands of work hours from start to finish. The result is a beautiful interactive map containing every single street tree in the city. If you’re a New Yorker and wondered what the name of that strange tree in front of your apartment was, now you can find out.
Why does the NYC Parks department spend so much time counting trees? The value that trees provide to a city can seem like a nebulous concept, but thanks to a tool developed by the US Forest Service, it can be converted into a dollar amount. For New York City that number is $151,315,411. The largest benefit is aesthetic. Streets planted with trees simply look better. Research by the Forest Service found that a tree in front of a house increases the sale price by about $7100 and that a home on a tree-lined street spends almost 2 days less on the market.
The second largest benefit is interception of stormwater. Because of tree canopies, the rain has a chance to evaporate from the leaves instead of reaching the ground. The amount of flash floods is reduced, since street drainage has to cope with less water. Urban stormwater pollution of lakes, streams, and oceans also goes down. Another benefit is energy savings from heating and cooling. During winters trees shelter homes from the winds, and during summers they provide shade, reducing the heat island effect. The temperature under the trees can be as much as 2 – 9 F cooler.
Removing air pollutants and reducing carbon dioxide is yet another service trees provide. And that’s not all. The calculations don’t include the benefits to wildlife and psychological and physiological benefits to less wild animals – us humans. Research shows that being near trees reduces stress, lowers blood pressure, makes us heal faster and feel healthier.
Thanks to the census reports, the city knows the exact locations of all street trees, so they can budget and prioritize the next planting initiatives. 28% of planting locations, which translates into 260,000 trees, are still unoccupied. So what can we learn from 20 years of careful tree observation? Lets look at the data and find out.
Since 1995, more than 160,000 trees have been planted in New York City, an increase of 35%. In 2007 mayor Michael Bloomberg announced an ambitious tree planting initiative called MillionTreesNYC, a program with a goal to plant a million trees in ten years. In November 2015, two years ahead of schedule, the millionth tree (really the 1,017,634th) was planted at Joyce Kilmer Park in the Bronx. New trees were planted in every single zip code, in parks, private yards, and of course streets.
So which borough can claim to have the greenest streets? That title goes to Staten Island with 129 trees per street mile. Manhattan is a close second with 121 trees. Brooklyn comes in last with only 97 trees per mile. More than 20 years ago the greenest borough was Queens with 98 trees per mile, while Bronx had only 60 trees per mile. Out of the five boroughs, Staten Island experienced the biggest increase in tree density between 1995 and 2005 while Bronx greenified fastest between 2005 and 2015. The borough that saw the lowest increase in the number of trees during the last decade is Queens.
The most common tree in the city these days is London planetree, but that was not the case 20 years ago. In 1995, Norway maple had that title, and there were almost 20,000 more of them than there are London planetrees today. Now Norway maple is the 5th most common tree in the city.
Why did more than 70,000 maples disappear from the streets? Was it a terrible fungus that decimated their population? Termites with a hankering for some Norwegian wood? In 1996, they were indeed being killed by a beetle. According to New York Times, “The New York City Department of Parks and Recreation has had to remove infested Norway maples from entire city blocks,” but the dead trees were never replaced. It is not as tragic as it sounds though, rather the opposite. New York City has been trying to reduce the number of Norway maples because it is an invasive species native to Europe and Western Asia. They seed very easily and grow quickly, outcompeting native trees. The large canopy of a full-grown tree is very dense, creating too much shade and preventing native flora from growing underneath. It has even been called New York’s ultimate weed.
Besides London planetree, the three species that can be seen most often in the streets are honey locust, Callery pear (also called Bradford pear), and pin oak. Coincidentally, these same trees have been the best at weathering hurricanes.
When hurricane Sandy hit New York city in 2012, the inflicted damage had the second highest price tag in the United States’ recorded history. That damage was still evident three years later and can be seen in the tree census. In 1995, there were about 19,000 dead trees and stumps. In 2015, that figure was over 31,000. The maps show where the devastation was the most widespread. Each pink dot represents a dead tree or a stump. South of Staten Island, Coney Island, Rockaways, southwest Bronx are only some of the areas that went from having relatively few dead trees to being riddled with them. As reported by the New York Times, “the storm struck the city’s trees like a chain saw on methamphetamines, toppling more than 8,000 street trees and destroying thousands more in parks and woodlands. That is twice the number of trees that came down last year during Tropical Storm Irene and triple the loss from a tornado the year before that.” The figure of 8000 only accounts for immediate damage. A lot of the trees were flooded for hours, with saltwater seeping into the roots. It wasn’t obvious those trees were dead until next spring when thousands of them failed to sprout leaves.
Six years have passed since Sandy, and New Yorkers are more likely to see a newly planted tree like this gingko in Crown Heights than a stump, and that’s something worth celebrating. If you live in New York City, and there’s a dead tree on your street or an empty planting space, you can request a tree by calling 311 or submitting a request online. If you would like a free tree to plant on your property, you can contact the New York Restoration Project. If you don’t live in New York City, don’t despair. Googling “request a tree [your city]” might turn up similar projects. Here’s one for Baltimore, Seattle, and LA.
Notes: The data used for this research is the tree census data done in 1995, 2005, and 2015. The data is provided by the Department of Parks and Recreation and owned by NYC OpenData. All of the trees in the neighborhoods that are not part of New York City such as Mt. Vernon are excluded. For all of the visualizations except the last one, only alive tree records are used, i.e. stumps and dead trees are excluded. 10,761 trees of unknown status from 1995 are excluded from all of the graphs, since it is not known whether those trees are dead or alive.
- To get the street tree densities in the second visualization, tree counts are divided by the number of street miles in each borough. The 2001 street data was found at fcny.org.
- For the Most Common Trees visualization, the trees shown are the top 10 trees for 2015. Trees in the top 6 for 1995 and 2005 are present, however, others are not shown to not clutter the graph. Excluded trees include green ash, red maple, silver maple, and sugar maple. There are 9300 unknown alive trees in 1995, 17,505 unknown alive trees in 2005, and 5 unknown alive trees in 2015. They do not appear in this visualization.
- 2005 data was not used for the last visualization, because stumps are missing from the dataset.
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