Carbon is a naturally occurring element. It is also part of carbon dioxide (CO2), an odorless gas that is produced in a variety of ways. We exhale carbon dioxide when we breathe. Carbon is emitted when fossil fuels are burned for energy. Vehicles and factories can also release it into the atmosphere.

While carbon dioxide is necessary for plants to generate oxygen, too much carbon dioxide in the air is believed to contribute to climate change.

The process of storing carbon, called sequestration, is a natural product of tree growth. Through photosynthesis, trees absorb carbon from the atmosphere in their leaves, roots and wood fiber, and release oxygen in the same process. Trees also continue to store that carbon.

Because of their faster growth rate and higher overall "metabolism," young trees soak up and store carbon quickly. As these young trees age and "get filled up" with carbon, they continue to absorb and store it, but at a slower rate.

All the good that comes from storing carbon in trees goes away if over-mature trees decay and die, or if they're burned in forest fires. In either case, the carbon that had been stored is released back into the atmosphere.