Teaching Physics with the Physics Suite

Edward F. Redish

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Can Trees Save the Planet?

A. Trees extract carbon dioxide (CO2) from the air and bind the carbon into their structure. Growing trees is therefore one way of reducing the amount of CO2 in the atmosphere (and burning them is a way of increasing the amount of CO2 in the atmosphere). About 45% of a tree’s dry mass is carbon and about 25% of the mass of a CO2 molecule is carbon. Estimate the mass of CO2 that is removed from the atmosphere by a single full-grown tree.

B. One report states that the human population of the earth was responsible for emitting 2.4 x 1013 kg of CO2 into the atmosphere in the year 2000 as a result of the burning of fossil fuels. If we decided to capture all the CO2 emitted from burning of fossil fuels by planting new forests, estimate how many square kilometers we would have to convert to forest each year to achieve this goal.

Page last modified March 2, 2009: G36