For human health and happiness, cities need more trees.
New York is usually represented by images of concrete, steel, traffic and skyscrapers. But green space, especially the tree canopy provided by the urban forest all around us, is as fundamental to healthy, comfortable city living as any man-made infrastructure. Policymakers and residents need to treat trees accordingly, putting a priority on wise, long-term investments that close a massive canopy gap that continues to divide neighborhoods along race and class lines. There are hopeful signs that the city government is already moving in this direction, but we need to do much more, and faster.
Why do trees matter?
Research is clear that they have tangible effects on our individual and collective well-being. They store and sequester carbon — an absolutely crucial quality in an era of climate change. They filter stormwater. They improve air quality. They provide homes for birds, squirrels, bats and other creatures that keep the city’s ecosystem lively and healthy.
Perhaps most importantly, in an era of intensifying heat, they cool the surfaces and air around them. Research shows that shaded surfaces can be up to 45 degrees Fahrenheit cooler than those that are unshaded. A recent analysis by New York City’s Department of Health and Mental Hygiene shows a 2 degrees Fahrenheit air temperature difference between blocks that are heavily vegetated versus those that are not. A change of a couple of degrees may seem minor, but it’s not — because heat stress takes lives.
Extreme heat and flooding are already upending the comfort and safety of New Yorkers. Heat contributes to the deaths of an estimated 370 New Yorkers each year. The heat-related death rate of Black New Yorkers is twice that of white New Yorkers.
New York City needs to treat trees, and their verdant canopy cover, as a necessity and not an amenity in all neighborhoods.
Without rapid and aggressive action, all this is going to get worse. The New York City Panel on Climate Change, the independent city advisory body that synthesizes scientific information on climate change to inform government policy, projects five to seven times the number of heat waves and 1.5 times the extreme precipitation events later this century.
New York City needs to treat trees, and their verdant canopy cover, as a necessity and not an amenity in all neighborhoods. This means both taking care of the ones we have and planting many more — using a pragmatic and well-funded plan that cuts across city agencies and serves have- and have-not neighborhoods alike.
The state of the canopy
What I refer to as the urban forest is all of the trees in the city, along with their tree beds and soil and all parts of their interconnected system. It ranges from single trees planted on sidewalks to landscaped groves in our parks to densely contiguous forested natural areas. Urban forests are highly managed systems that, to thrive, require significant human attention, including professional arborists, volunteer stewards, climbers and pruners, home gardeners and more.
In the five boroughs, we have more than 7 million trees spanning just over 300 square miles of public and private land, which works out to about 23,000 per square mile of land. That makes our tree density greater than Philadelphia’s (134 square miles and about 2.9 million trees), about 21,500 trees per square mile; and Los Angeles’ (470 square miles and about 10 million trees), about 21,000 per square mile; but far less than Dallas’ (345 square miles and close to 15 million trees), about 43,500 per square mile.
But New York’s relative standing is only one way to gauge our success or lack thereof. Another way to put it: As of 2017, trees covered 22% of the five boroughs, up from 20% in 2010. In this way, New York was bucking the trend —many cities in the U.S. were losing tree canopy over a similar time period.
We know all this because tree canopy is mapped with 3D data collected using a high-tech tool called lidar, a remote sensing method that uses the same principles as radar, but using light from a laser. This data is available from 2010 and 2017 for New York, hence the timeframes discussed here.
Now the bad news: Canopy coverage is glaringly disparate across New York due to both historic and present factors.
Unsurprisingly, Staten Island is the leafiest borough, with about 31% canopy cover. Brooklyn, the most populous borough, is the most sparsely covered, at less than 18%. When we look at neighborhoods, that range is much wider, from under 10% in Hunts Point, East Williamsburg, Sunset Park and Midtown South to over 50% in Riverdale. Airports and parks and cemeteries provide even further extremes. Perhaps all too predictably, lower-income communities and communities of color tend to have less coverage, which is a big part of what makes them more vulnerable to heat. And systemic racism, including the legacy of historic redlining and current disparity in access to cooling, safe housing and health care resources, deepens these divides.
We should all viscerally understand how it feels to be in low-canopy neighborhoods with little respite from the blazing sun and radiating heat on those dog days of summer. It’s why we cross to the shady side of the street every chance we get. Every year we allow these disparities to persist, we consign swaths of the city to a bleaker future.
A significant piece of the problem is that the city’s urban forest isn’t managed, or regulated, in a coordinated fashion.
Over half of our tree canopy, 53.5%, is overseen by the hardworking yet chronically underfunded Department of Parks and Recreation, whose advocates have been fighting tirelessly for years to try to secure a scant 1% of the City budget to care for about 14% of the city’s land (plus having jurisdiction over street trees!).
Urban forests are highly managed systems that, to thrive, require significant human attention, including professional arborists, volunteer stewards, climbers and pruners, home gardeners and more.
To break that down further, the Parks Department oversees the more than 28% of the city’s total canopy that’s on parkland, plus the 25% of total citywide canopy that spans our streets and sidewalks. This is the best and most consistently managed section of the urban forest. About 3% of the canopy is on other city-owned property. Nearly 8% of the canopy is on state and federal lands. And a whopping 35% is on private property, wholly unprotected.
Some fairly recent government investments are helping put more trees where, in many cases, people need them most.
In 2007, the Bloomberg administration launched MillionTreesNYC to accelerate planting across the whole city, and a program called Trees for Public Health was folded in, prioritizing planting to improve air quality in communities with fewer-than-average street trees and higher-than-average rates of asthma among young people. Some of the Trees for Public Health neighborhoods, like the South Bronx, exhibited relatively high rates of canopy expansion from 2010 to 2017, an early sign of potential success, though the planted trees remain young; they need care and protection to reach their potential.
The city planted that millionth tree in 2015, two years ahead of schedule, and since then, Cool Neighborhoods NYC, launched in 2017, intended to support planting of 11,000 street and park trees in the most heat-vulnerable neighborhoods, with nearly 15,000 more to be planted through Spring 2024. In 2022, the City allocated an additional $112 million to support 36,000 trees to be planted each year in other extremely heat-vulnerable neighborhoods through 2026. And this program complements the broader ongoing tree planting efforts of the City, including a request-based system for street trees and ongoing planting in landscaped parks and forested natural areas. To date, this year’s planting is higher than the past five. Still, keeping pace with this commitment will require aggressive action.
In lower-income neighborhoods, and those that are predominantly Black and Latino, the coverage levels were subpar. So despite all this progress, on the whole and especially in many lower-income communities and communities of color, the level of vegetation cover remains too low to meaningfully and equitably cool our communities and offer other important benefits.
A new goal: 30% tree cover across the city
The Adams administration, and many other elected leaders, seem to understand this. As part of the recently released PlaNYC, the administration established a goal of achieving 30% tree canopy cover citywide to address extreme heat. Twenty-eight members of City Council also endorsed achieving this goal by 2035, as well as all five borough presidents. This echoes the calls from Forest for All NYC, and their NYC Urban Forest Agenda. (Disclosure: My employer is a leading member of the coalition, and I’m an architect of the coalition’s report.)
Why does 30% matter? Researchers from the City’s Department of Health and Mental Hygiene showed that for vegetation to be used as a strategy to decrease local temperatures, at least 32% vegetation cover (that includes trees, shrubbery and other green stuff) is needed. Thirty percent tree canopy cover should be viewed as the floor, not the ceiling, in order to achieve this broader vegetation goal.
This is ambitious but wholly possible. A recent study showed that, even without making big changes to our built environment, there is fertile ground, and sufficient overhead space, for canopy expansion in every community across New York City.
Of course, we can’t just plunk trees in low-canopy, heat-vulnerable neighborhoods and consider our work done, lest we bring to life the Onion headline, “Trees Planted in Poor Neighborhood Mature Just in Time for Gentrification.” We have to deeply engage in local communities, provide employment and stewardship opportunities and plant in a smart way that’s consistent with residents’ priorities. For lasting success, existing trees need protection and professional maintenance, as well as training and support for local stewards.
To realize 30% canopy equitably, we need a strategy with a timeline — per the NYC Urban Forest Agenda, I suggest a target date of 2035 — and the necessary resources to execute it. The good news is that City Council is contemplating mandating just such an approach in newly introduced legislation, met with resounding public support, that not only requires a plan but also ongoing monitoring of the state of the canopy as well as integrating tree planting and management into the city’s sustainability planning.
A greener way forward
Protecting the trees we have, especially larger and older trees, is the first necessary task. Akin to our housing stock, we can’t be seduced by the new and wind up neglecting the old.
To that end, we should follow the lead of other cities and give more legal protections for more trees by passing an ordinance and zoning for all communities that prioritizes tree preservation. Interesting examples to spur dialogue and consider what could work in the New York City context include Washington’s Special Tree Removal Permits, Atlanta’s newly updated ordinance and San Antonio’s rules. We also need incentives for private landowners to maintain and expand the canopy on their properties — in the form of tree giveaways, utility rebates or tax incentives.
Simultaneously, we should heed the growing chorus of voices to plant a million more trees by 2030, as championed by the uncharacteristically unanimous borough presidents and many Community Boards across the city. While planting trees alone, even a lot of them, can’t guarantee we reach 30 percent canopy, if we protect what we have, achieve the borough presidents’ vision and then keep going, we will be well on our way.
We should all viscerally understand how it feels to be in low-canopy neighborhoods with little respite from the blazing sun and radiating heat on those dog days of summer. It’s why we cross to the shady side of the street every chance we get.
It’ll take more money, but there are savings to be had. And trees are perhaps the only municipal infrastructure that increase in value after installation. To do the work efficiently, we must untangle the thorny challenges that slow municipal tree planting and maintenance efforts. Planting timelines are notoriously slower than hoped, and the price tag, especially for street trees, can cause sticker shock. To be fair, those price tags aren’t just the cost of a tree. They include preparing a tree bed, soil, a robust tree grown to specification, planting, and a two-year warranty which requires care and watering.
Still, the prices are high and the timelines are too long. We can make planting more cost-effective and speed things up by reforming onerous procurement rules, expanding the pool of qualified contractors, be they nonprofit or for-profit, continuing our long-term contracts with growers to ensure adequate tree stock and potentially developing and fully funding an in-house planting workforce at the Parks Department, which would also expand good green jobs for New Yorkers.
We need to find better ways to enlist more people — government workers and others, paid and volunteer — in planting and maintaining trees. After doing a robust assessment of the actual workforce need and committing to funding it, the city should baseline all forestry positions — meaning, build them into future budgets, just as we do with other pieces of the municipal workforce. And it should go without saying, but these jobs need to pay well and be accessible via local training such that local people can afford to live in the city they so lovingly tend. At present, some forestry jobs don’t need to be filled by those who live in the five boroughs.
Municipal and nonprofit staff can’t do it all. New Yorkers themselves, and our vast network of community organizations, should be more effectively engaged in planting and maintenance, getting support and, where appropriate, money, to be on-the-ground stewards. The private sector needs to play a bigger role in planting and growing trees on its own land; we can design incentives to make that happen.
Not least, it’s imperative to measure our progress to make sure we are expanding the total urban forest and closing the canopy gap. City government should routinely track tree canopy as we do other important environmental and public health measures, which can be done by collecting and analyzing LiDAR data at least every three years.
And, as always, our municipal budget needs to reflect these priorities.
With increasingly hot summers upon us, it’s time to make sure the seeds grow into saplings and then full-grown trees that are broad and tall and strong and sheltering. If we take care of them, they’ll take care of us.
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