Reported May 2007

BACKGROUND: As part of a research project, students and faculty members at the State University of New York’s College of Environmental Science and Forestry have determined the precise combination of trees that would be most effective in reducing the level of greenhouse gases in the air around Syracuse, New York. If the combination of trees were planted it could reduce carbon dioxide – a greenhouse gas -- by 2% by the year 2046, the team estimates. While the initial recommendations are just for New York, the project members can give recommendations for all across the United States.

HOW IT WORKS: During photosynthesis, trees remove carbon from the atmosphere and store it away in the tree’s wood. This process is known as sequestration, and it reduces levels of carbon dioxide in the air. Trees also provide shade and lower air temperatures, reducing the amount of energy that buildings use and, therefore, the amount of work required – and carbon dioxide released – by power plants. Trees with denser wood, such as hawthorn trees, are most effective at removing carbon dioxide from the air. Other trees emit volatile organic compounds, which contribute to the formation of ozone. Ozone in the upper levels of Earth’s atmosphere can have a protective effect, but particles of ozone in the air we breathe are considered pollutants.

A WINNING COMBINATION: To create the ideal combination of trees for Syracuse, the group chose trees with the best carbon-sequestering ability and lowest emissions of volatile organic compounds. Large and long-lived trees are crucial, particularly for the shade they provide. The SUNY group also recognized that it was necessary to include a lot of different types of trees, and avoided trees that are very susceptible to disease, such as the American elm. Based on these criteria, the group suggested that the optimal vegetation for Syracuse would be a group of 31 different types of trees, including dogwood, red hickory and hawthorn. Furthermore, the trees would be most valuable if they were planted in the center of the city, where areas of continuous asphalt typically send CO2 straight into the atmosphere.

ABOUT PHOTOSYNTHESIS: Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. This process occurs in plants and some plant-like algae. Plants need only light energy, carbon dioxide and water to make sugar. The light reaction converts light energy to chemical energy via chlorophyll, a green pigment, and several other pigments such as beta-carotene. Each differently-colored pigment can absorb a slightly different color of light and pass its energy to the central chlorophyll molecule to do photosynthesis. The energy harvested via the light reaction is stored by forming a chemical called ATP, a compound used by cells for energy storage. The dark reaction converts carbon dioxide to sugar. This reaction doesn't directly need light in order to occur, but it does need the products of the light reaction (including ATP).

The American Geophysical Union contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

American Geophysical Union
Washington, DC 20009-1277
800-966-2481
http://www.agu.org