Urban Trees Fight CO2 Emissions

By Mays Jumah and Stevie Borrello

Forest Service scientists and colleagues found that trees play an important role in reducing fine particulate air pollution. An average of one life every year per city is saved by urban trees and forests. In New York City alone, trees save an average of eight lives each year.

Air pollution is a major environmental health risk. Urban trees can reduce pollution and improve our health by removing fine particles from the atmosphere. Lowering air pollution levels can help countries shrink the global burden of disease from respiratory infections, heart disease, and lung cancer. As air pollution levels in cities decrease, the populations’ respiratory (both long- and short-term) and cardiovascular health improves.

Researchers David Nowak and Robert Hoehn of the U.S. Forest Service with Satoshi Hirabayashi and Allison Bodine of the Davey Institute in Syracuse, NY estimated the amount of fine particulate matter that trees remove in 10 different cities. They also determined the impact trees have on PM_2.5 concentrations (fine particulate matter consisting of small, airborne particles with a diameter of 2.5 micrometers or less) and the associated effects on human health.

“More than 80 percent of Americans live in urban areas containing over 100 million acres of trees and forests… This research clearly illustrates that America’s urban forests are critical capital investments helping produce clear air and water, reduce energy costs, and, making cities more livable. Simply put, our urban forests improve people’s lives,” said Michael T. Rains, Director of the Forest Service’s Northern Research Station and Acting Director of the Forest Products Lab.

The cities included in the study are Atlanta, Baltimore, Boston, Chicago, Los Angeles, Minneapolis, New York City, Philadelphia, San Francisco, and Syracuse, NY. Due to its comparatively large human population, New York City has the greatest potential for improving its population’s health through trees.
However, Atlanta has the greatest overall air pollution removal occurs in because of its comparatively high percent tree cover and PM_2.5 concentrations.

In another study conducted by Dr. Klaus Lackner and Senior Staff Associate Allen Wright of Columbia University’s Earth Institute at the Lenfest Center for Sustainable Development, researchers designed a new project that sucks CO₂ emissions directly out of the atmosphere. In the study, an artificial tree soaks up carbon dioxide from the air using “leaves” which are 1,000 times more efficient than true leaves that use photosynthesis.

BBC reported that “The problem with removing carbon dioxide from the atmosphere is that it is present at such a low concentration. In a power plant chimney, for instance, carbon dioxide is present at concentrations of 4-12% within a relatively small amount of exhaust air. Removing the gas takes a lot of energy, so it is expensive, but it’s feasible. To extract the 0.04% of carbon dioxide in the atmosphere would require enormous volumes of air to be processed. As a result, most scientists have baulked at the idea.”

Dr. Lackner calculated that his tree is able to soak up one ton of carbon dioxide a day. Ten million of these trees could remove 3.6 billion tons in a year, which is equivalent to about 10% of our global annual carbon dioxide emissions. His invention helps clean up the waste that is constantly emitted into the atmosphere more quickly and more efficiently.

Mays Jumah is an Intern at the Earth Institute Center for Environmental Sustainability. She is a Jeanette K. Watson fellow studying Biology at the College of Staten Island.

Stevie Borrello is a student at the Macaulay Honors College. She is studying Journalism.