The invisible data:
ecological benefits
Street trees are not only for decoration – these trees put in a lot of work offsetting the effects of human activity and pollution. Below are charts that show just how much ecological benefits these street trees are providing for New York City.
The larger the tree, the bigger the ecological impact! The R-squared value for diameter versus stormwater intercepted is 0.94, diameter versus energy conserved is 0.89, diameter versus CO2 reduced is 0.84, and versus pollutants removed is 0.91. Below is a look at each of these individual ecological parameters, with context added for perspective on the magnitude of these numbers.
Stormwater interception
Trees intercept water by retaining it in the leaves and bark of the tree – part of it will evaporate, and the other part will seep into the soil. Stormwater interception can increase the water quality of the runoff, prevent erosion, and help organisms break down organic matter used for plant growth. It also returns more moisture to the soil rather than running off and carrying oil, metal particles, and other pollutants.¹
By comparing trees of similar sizes (diameters), we can see how stormwater interception amounts differ between species. Some of the largest trees (over 30 inches in diameter) intercept huge amounts of stormwater – with each tree intercepting anywhere from 5,664 to 8,638 gallons per year.
¹ How Trees Can Retain Stormwater Runoff, Arbor Day Foundation.
2,262,195 galstormwater intercepted annually by Fifth Avenue street trees
1,053,675,413 galstormwater intercepted annually by all NYC street trees
How many ten-minute showers does each tree intercept in stormwater each year?
Based on a shower head flowing at 2.5 gallons per minute (a common flow rate for shower heads), a single 10-minute shower uses 25 gallons of water.² The largest trees annually intercept almost a year’s worth of 10-minute daily showers, while the smallest trees intercept about a weeks worth. Combined, all Fifth Avenue street trees annually intercept the equivalent of almost 250 people’s daily 10-minute showers for an entire year.
² How Water Works, Indoor Water Use.
Energy conservation
By comparing trees of similar sizes (diameters), we can see how stormwater interception amounts differ between species. Honey Locusts and American elms conserve the highest amount of energy per year compared to other species of the same sizes. Energy amounts conserved differ by anywhere from 500-1,500 kWh for each different size tree. The average American home uses about 10,715 kWh (kilowhatthours) per year, averaging to 883 kWh per month.¹ It would take four large Elm trees (say 40 inches in diameter each) to conserve the amount of energy the average American home consumes in a year.
¹ US Energy Information Administration
1,343,330 kWhenergy conserved annually by Fifth Avenue street trees
649,263,466 kWhenergy conserved annually by all NYC street trees
How long could each tree keep a television on?
If you were to keep a TV on continuously (24 hours a day), how many months would each type/size of tree be able to keep it on? This calculation is based on a 40 inch HD TV and the amount or energy (kilowhatthours) a tree conserves annually.² The largest Elms and Japanese Zelkovas (over 30 inches in diameter) conserve enough energy each year to keep a television continuously on for over a year.
² How much electricity do my home appliances use? IGS Energy
Carbon dioxide reduction
By comparing trees of similar sizes (by diameter), we can see how reduction in CO2 amounts differ between species. American Elms reduce the most amount of CO2 per year, compared to other species of the same sizes. Combined, all of Fifth Avenue’s street trees annually offset over 161,600 people’s carbon footprints.¹
¹ How to help: Calculate your carbon footprint. The Nature Conservancy.
2,263,415 tonsCO2 reduced annually by Fifth Avenue street trees
1,177,000,498 tonsCO2 reduced annually by all NYC street trees
How many people’s carbon footprints could each tree offset?
For comparison, the average person’s carbon footprint in the US is 14 tons/year. ² Don’t be fooled though – that’s still astronomically high. The global average is 4 tons per capita.³ In order to potentially avoid the 2˚C rise in global temperature, the average annual carbon footprint per person needs to be below 2 tons by 2050.⁴ If you’re curious about your carbon footprint, you can calculate it here.
²⁻⁴ How to help: Calculate your carbon footprint. The Nature Conservancy.
The average person’s carbon footprint in the US is 14 metric tons / year. Vehicle use accounts for 4.6 metric tons (or about 33%) of this. Food (meat), consumption, and energy are the other main contributors.
Air pollutants removal
Air pollution in New York City comes from a variety of sources, both inside and outside the city. Major contributors include on-road and off-road vehicles, fossil fuel combustion for generating electric power and heating, and commercial cooking.¹ Other particles can also enter the air from construction, demolition, or road dust.² These can cause increased lung and cardiovascular health risks.³ Trees help remove air pollutants (by uptake via leaf stoma, by the plant surface, absorption, or reception through leaves),⁴ creating cleaner air.
¹⁻³ Air Pollution and the Health of New Yorkers. NYC Health. ² U.S. Environmental Protection Agency, National Emissions Inventory. ⁴ Nowak, David J. 2002. The Effects of Urban Trees on Air Quality. USDA Forest Service.
2,928 lbsair pollutants removed annually by Fifth Avenue street trees
1,231,548 lbsair pollutants removed annually by all NYC street trees
How many pounds of air pollutants are removed each year by a single tree?
For context and comparison, a single gallon of gas emits almost 19 lbs of air pollution in the form of carbon dioxide, and a single gallon of diesel fuel emits about 22 lbs.⁵ That’s more than two times the amount of air pollution the largest elm on Fifth Ave removes in a year – and that doesn’t even include the emissions from fuel production.
⁵ Carbon Dioxide Emissions Coefficients, U.S. Energy Information Administration.
Curious what your footprints are?
Though corporations should hold most of the responsibility, our collective individual actions still have a substantial impact on the environment. Get familiar with your water usage, energy consumption, waste habits, and carbon emissions.