Some parts of a recent letter to the editor regarding the role of trees in the carbon dioxide cycle were misleading. Trees do store carbon in a process called sequestration, in which carbon dioxide is removed from the atmosphere and stored for a long period of time, not released at night. Carbon dioxide is rereleased only when the tree dies and plant material decomposes.

In photosynthesis, the leaves of a tree use water, nutrients from the soil and carbon dioxide from the air with the sun’s energy where oxygen is not just released but created as a byproduct. During the day, the plant produces far more oxygen from photosynthesis than carbon dioxide from cellular respiration.

George Lane

professor, homeland security program, Tulane University

New Orleans