How a Massive Tree-Planting Campaign Eased Stifling Summer Heat in New York City

By Sonja Dümpelmann, Harvard University | January 28, 2019 11:30 am
New York City tree planting

In 1919, 1,376 new Norway Maples were planted along streets in Brooklyn. (Credit: Department of Parks of the Borough of Brooklyn, City of New York)

Many cities, in recent years, have initiated tree planting campaigns to offset carbon dioxide emissions and improve urban microclimates.

In 2007, New York City launched MillionTrees NYC, a program designed to plant 1 million new trees along streets, in parks and on private and public properties by 2017. They hit their goal two years ahead of time.

These programs are popular for a reason: Not only do trees improve the city’s appearance, but they also mitigate the urban heat island effect – the tendency for dense cities to be hotter than surrounding areas. Studies have shown that trees reduce pollutants in the air, and even the mere sight of trees and the availability of green spaces in cities can decrease stress.

But as I show in my new book, “Seeing Trees: A History of Street Trees in New York City and Berlin,” trees weren’t always a part of the urban landscape. It took a systematic, coordinated effort to get the first ones planted.

Hot, Congested – and Treeless

As New York City’s population exploded in the 19th century, poor sanitary conditions, overcrowding and hot summers made the city a petri dish for disease: Between 1832 and 1866, cholera outbreaks alone had killed an estimated 12,230 people.

By the turn of the 20th century, living conditions had deteriorated. Neighborhoods continued to be overcrowded, indoor plumbing was still lacking and open sewers could still be found along many of the city’s dusty streets and alleys.

people in streets of new york city a century ago

By the turn of the century, the city’s congested streets could be choked with people, but without a green leaf in sight. (Credit: Library of Congress)

Trees could be entirely absent from a neighborhood. The few trees that did line city streets – mostly ailanthus, elms and buttonwoods – could be individually cataloged with relatively little effort. For example, in 1910, The New York Times reported on the decreasing number of trees along Fifth Avenue. The article noted that between 14th Street and 59th Street, there were only seven trees on the west side and six on the east side of the avenue.

Real estate development, subway expansion and utility line construction had clearly taken their toll.

A Physician Proposes a Solution

In the 1870s, eminent New York City physician Stephen Smith spearheaded a movement to plant more trees. Doing so, he argued, would save lives.

stephen smith

Physician and public health advocate Stephen Smith. (Credit: Wikisource)

Smith, who pioneered the city’s sanitary reforms and founded the Metropolitan Board of Health, was the author of a groundbreaking study that correlated high temperatures with childhood deaths from a number of infectious diseases. He concluded that planting street trees could mitigate oppressive heat and save 3,000 to 5,000 lives per year.

To promote street tree planting in his city, Smith drew attention to what became known as the Washington Elm study.

Attributed to Harvard College mathematics professor Benjamin Peirce, the study claimed that the famous Washington Elm standing on the Cambridge Common in Massachusetts had an estimated crop of 7 million leaves that, if laid out next to each other, would cover a surface of 5 acres. The study illustrated the vast potential of a single tree’s foliage to absorb carbon dioxide, emit oxygen and provide shade.

In 1873, Smith drafted and introduced his first bill to the New York state legislature for the establishment of a Bureau of Forestry, which would promote the cultivation of street trees.

But the bill stalled; it took several additional attempts and amendments before it was finally approved in 1902. Even then, it didn’t provide adequate funds for municipal street tree planting. So, in 1897, Smith joined a group of citizens who decided to take matters into their own hands. Calling themselves the Tree Planting Association, they helped homeowners plant trees in front of their residences. A few years later, they also established the Tenement Shade Tree Committee to plant trees along tenement blocks and in front of public schools.

The city encouraged residents living on a block to collaborate on planting decisions so that trees could be planted at regular intervals, providing even shade and a uniform aesthetic. Some species, like the Norway maple, were favored because of their tall trunks and their ability to grow in poor soil and withstand urban pollution.

The association’s first list of members read like a New York City “Who’s Who”: philanthropist and housing reformer Robert de Forest; art dealer Samuel P. Avery; sculptor Augustus St. Gaudens; industrialist and former mayor Edward Cooper; and financiers J.P. Morgan, W. Bayard Cutting and William Collins Whitney.

Front Lines of Fighting Climate Change

For these early activists planting trees was a way to cool streets and buildings in the summer and beautify the city’s gritty urban landscape.

Only later would scientists come to realize the enormous potential that urban trees besides entire forests held in mitigating the effects of climate change.

In 1958, Chauncey D. Leake, president of the American Association for the Advancement of Science, warned of the warming atmosphere in a well-received paper at the National Conference on Air Pollution. He pointed out that warming temperatures could cause the huge polar ice caps to melt, leading to sea-level rise. To lower levels of carbon dioxide in the atmosphere, he suggested planting 10 trees for every automobile and 100 for every truck.

Leake’s proposal was an early attempt at using tree planting to offset global warming. Since then – and particularly over the last two decades – methods that calculate the number of trees needed to offset carbon dioxide emissions have become more sophisticated. For this purpose scientists and foresters from the U.S. Forest Service and the University of California Davis developed iTree, a suite of software tools that help to determine a tree species’ ability to sequester carbon, reduce pollution and decrease storm water runoff in a particular ecosystem.

Despite their popularity, new trees can be met with resistance. While many residents enjoy the shade and look of a tree, there’s always someone who sees them as a nuisance that blocks sunlight from entering their apartment. Others complain about the smelly flowers that some trees produce, the seeds they shed, and the way they attract birds that speckle sidewalks with their droppings.

But as the perils of climate change become more apparent, the hope is that the broader benefits of trees prevail over personal predispositions.The Conversation

Sonja Dümpelmann, Associate Professor of Landscape Architecture, Harvard University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

CATEGORIZED UNDER: Environment, Top Posts
  • OWilson

    Now THERE’S a program I can get behind!

    And as especially where, my favorite, the King of pollution and air conditioning, the amazing Norway Maple is concerned. They keep Toronto cool, and healthy and beautiful.

    Having grown up in post war Europe in a city where all accessible trees were chopped down for fuel, I made it a hobby to plant Norway Maples wherever I could in over 2 continents, where I have lived and worked. Unlike many of the more quick growing weed trees that developers plant for cosmetic purposes, they are long lasting and storm resistant.

    Many are still thriving, and thanks to Google Stree View, I can get satisfaction from how they have grown, almost like my children. Squirrels and woodpeckers love them too!

    You greeners out there, stop lecturing, plant a tree, you’ll feel good!

    • Erik Bosma

      I didn’t know you were a fellow Canuck. Thought you lived on an island in the Caribbean or somewhere like that.

      • OWilson

        Yep! But born and raised in the U.K. Ran a business and raised a family in Toronto, then back to the U.K. for a 5 year stint doing Educational Research and teaching, which took me to Eastern Europe, after the Wall came down.

        Then, after 8 years of visiting mi “La Isla Bonita”, decided to make it my home.

        I didn’t mention planting any trees here because trees grow so aggresively and profusely anywhere they can find an open spot. :)

  • Dean Jackson

    “The study illustrated the vast potential of a single tree’s foliage to absorb carbon dioxide, emit oxygen and provide shade.”

    Tree absorption of carbon dioxide was thought good because the molecule was believed to be a poisonous gas, while producing “health-giving oxygen”. The cooling effect itself would be provided by the trees (1) providing shade; and (2) evaporation. There was no absurd ideas about tree absorption of carbon dioxide cooling the environment.

    Google (the book, ‘Seeing Trees: A History of Street Trees in New York City and Berlin’): benjamin peirce planting trees

    The article insinuates that carbon dioxide is warmer than the surrounding air which is absurd, since it’s been known for close to 200 years now that carbon dioxide contains LESS heat than nitrogen and oxygen, approximately one-third less heat, which is why carbon dioxide is denser than air.

    Carbon Dioxide, Nitrogen and Oxygen: A Remedial Lesson In Chemistry and Physics…

    CO2 is a denser molecule than either N2 and O2 – one-third denser due to one-third less heat contained in the CO2 molecule – which informs us that CO2 COOLS the atmosphere by displacing greater heat retaining N2 and O2 molecules. CO2 has always been known to be a cooling molecule, as confirmed in 1979 when the BBC weekly science program, Tomorrow’s World, informed us that carbon dioxide is a “coolant gas”. Fast-forward 11:00 minutes into the program for the shocking admission:

    Google (only use the Google search engine): tomorrows world review of the 70’s

    This informs us that man is mediating the atmosphere, not changing it, because the real culprit for the heating of the atmosphere is the massive increase of man made structures on the ground that act as enhanced heat sinks while also decreasing the cooling effect of vegetation at night. If one desires less heat, the mechanism to be used is to INCREASE CO2 levels, not decrease those levels. Increases of CO2 into the atmosphere actually tempers the current warming of the planet. Note: ‘Climate change’ frauds naturally remain silent regarding the heat generated by man made structures on the ground.

    We are additionally informed of (1) the false opposition to ‘climate change’, who self-identify themselves as Marxist operatives by regurgitating Marxist carbon dioxide talking points; or (2) those scientists/teachers who are cowered from speaking the truth regarding carbon dioxide’s cooling nature on Earth.

    Cooling of Atmosphere Due to CO2 Emission, G. V. CHILINGAR, L. F. KHILYUK, and O. G. SOROKHTIN, Energy Sources, Part A, 30:1–9, 2008


    Traditional anthropogenic theory of currently observed global warming states that release of carbon dioxide into atmosphere (partially as a result of utilization of fossil fuels) leads to an increase in atmospheric temperature because the molecules of CO2 (and other greenhouse gases) absorb the infrared radiation from the Earth’s surface. This statement is based on the Arrhenius hypothesis, which was never verified (Arrhenius, 1896). The proponents of this theory take into consideration only one component of heat transfer in atmosphere, i.e., radiation. Yet, in the dense Earth’s troposphere with the pressure pa > 0:2 atm, the heat from the Earth’s surface is mostly transferred by convection (Sorokhtin, 2001a). According to our estimates, convection accounts for 67%, water vapor condensation in troposphere accounts for 25%, and radiation accounts for about 8% of the total heat transfer from the Earth’s surface to troposphere. Thus, convection is the dominant process of heat transfer in troposphere, and all the theories of Earth’s atmospheric heating (or cooling) first of all must consider this process of heat (energy)– mass redistribution in atmosphere (Sorokhtin, 2001a, 2001b; Khilyuk and Chilingar, 2003, 2004).

    When the temperature of a given mass of air increases, it expands, becomes lighter, and rises. In turn, the denser cooler air of upper layers of troposphere descends and replaces the warmer air of lower layers. This physical system (multiple cells of air convection) acts in the Earth’s troposphere like a continuous surface cooler. The cooling effect by air convection can surpass considerably the warming effect of radiation. …

    Global Atmospheric Cooling due to Increase in CO2 Content

    Increase in CO2 content leads to global cooling of atmosphere. This paradoxical, at first sight, conclusion can be inferred from the adiabatic theory of heat transfer. To compare the temperature characteristics of a planet at various compositions of its atmosphere, one can use Eq. (11).

    If one assumes that the existing nitrogen–oxygen atmosphere of Earth is replaced entirely by an imaginary carbon dioxide atmosphere with the same pressure of 1 atm and adiabatic exponent ˛ D 0:1428, then the value of b˛ D 1:5970:1428 D 1:069 and the near-surface temperature would decline to 281.6 K. Thus, the atmospheric temperature would decreases by 6.4ıC, instead of increasing according to the traditional theory.

    Similarly, if one assumes that the existing carbon dioxide atmosphere of Venus is entirely replaced by the nitrogen–oxygen atmosphere at the same pressure of 90.9 atm, then its surface temperature would increase from 735 to 796 K. Thus, increasing the saturation of atmosphere with carbon dioxide (despite its radiation absorbing capacity), with all other conditions being equal, results in a decrease and not an increase of the greenhouse effect and a decrease in average temperature of planet’s atmosphere.


    Accumulation of large amounts of carbon dioxide in the atmosphere leads to the cooling, and not to warming of climate, as the proponents of traditional anthropogenic global warming theory believe (Aeschbach-Hertig, 2006). This conclusion has a simple physical explanation: when the infrared radiation is absorbed by the molecules of greenhouse gases, its energy is transformed into thermal expansion of air, which causes convective fluxes of air masses restoring the adiabatic distribution of temperature in the troposphere. Our estimates show that release of small amounts of carbon dioxide (several hundreds ppm), which are typical for the scope of anthropogenic emission, does not influence the global temperature of Earth’s atmosphere.”

    The greatest point to be made is that the atmosphere is heated by nitrogen and oxygen, a fact that ‘climate change’ frauds refuse to discuss! Imagine that, how did it occur that nitrogen and oxygen are taboo molecules for ‘climate change’ frauds? It occurs because if ‘climate change’ deceivers had to discuss nitrogen and oxygen, they’d have to inform the public that those two molecules hold more heat than does carbon dioxide, and that would (1) implode the ‘War on Carbon Dioxide’; and (2) implode the purpose for the ‘War on Carbon Dioxide’: To weaken the West’s economies. What we have then is a reverse of the ‘Earth’s energy budget, where thermals should be 398.2 Wm2, and ground emitted infrared radiation 86.4 Wm2. Talk about a massive conspiracy of scientific fraud that the Marxist media naturally refuses to report.

    Then to compound this conspiracy, we have NASA, and other ‘educational’ institutions, telling us that nitrogen and oxygen don’t even absorb infrared radiation!:

    “It has been understood since the 19th century that some gases absorb infrared radiation (IR) that is emitted by the planet, slowing the rate at which the planet can cool and warming the surface. These so-called greenhouse gases include carbon dioxide and water vapor, as well as ozone and methane among others. Note, however, that the bulk of the atmosphere is made up of nitrogen and oxygen molecules which don’t absorb IR at all.”

    It’s been known since 1949 that nitrogen and oxygen do absorb infrared radiation:

    “Due to their symmetry, homonuclear diatomic molecules like N2 and O2 do not exhibit a static electric dipole moment, such as H2O, nor is there the possibility to induce vibrationally a dipole moment, as in the case of CO2. Thus, there are no strong infrared absorption bands due to dipole transitions as in the case of the major greenhouse gases. However, as discovered by Crawford et al. [1949], collision-induced absorption leads to weak absorption features of N2 and O2 in the infrared [e.g., Hartmann et al., 2008].”

    The peer reviewed paper affirms the non-negligible roles that Oxygen and Nitrogen play, in the aggregate, in heating the atmosphere. …

    “This work challenges a common perception on the negligible role of O2 and N2 as natural greenhouse gases in the Earth’s atmosphere compared to species like CH4 or N2O. It is in fact the large abundance of oxygen and nitrogen which compensates for their only weak interaction with infrared radiation through collision-induced absorption bands.

    Due to the atmospheric concentration of atmospheric N2 (O2) that is about 2000 (550) times higher than that of CO2 and about 4.4 X 105 (1.2 X 105) times more abundant than CH4, even the weak infrared absorption of N2 (O2) can become radiatively important.”

    At my blog, read the articles…

    ‘Throwing Cold Water on Global Warming’

    ‘The Marxist Co-Option Of History And The Use Of The Scissors Strategy To Manipulate History Towards The Goal Of Marxist Liberation’

    ‘House of Cards: The Collapse of the ‘Collapse’ of the USSR’

    ‘Playing Hide And Seek In Yugoslavia’

    My blog…

    Google (only use the Google search engine): djdnotice blogspot

  • CriticalDragon1177

    I wish we would plant more trees today, not to mention bushes and flowers.


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