Montana’s forests are a treasured resource of the state and a major influence in our quality of life.
Much of Montana’s 93 million acres is forested land – roughly 23 million acres. The trees and understory shrubs of Montana’s forests are an important component of the carbon cycle. But climate change may already be affecting the profile of Montana forest lands.
Trees, and by extension forests, remove carbon dioxide from the air. The photosynthetic process converts sunlight and carbon dioxide gas into carbon, some of which is stored as fiber in tree trunks and branches, foliage, and roots. During the process, some carbon dioxide is released back into the atmosphere. But more carbon is absorbed by trees than is transpired, making forests a net gainer in the equation.
Worldwide, forests store an astounding quantity of carbon derived from the atmosphere. At maturity, about 50 percent of a tree’s dry weight is carbon. The overall biomass of a forest and its soils acts as a “carbon sink,” effectively sequestering, or storing carbon. Even post-harvest, this carbon can be retained for decades as wood products used in housing, furniture, and other durable goods. As natural biological scrubbers of greenhouses gases, forests are highly productive, economical, and to a large extent, manageable.
But forests play additional and important roles in climate beyond the exchange of carbon. Living forests transpire large quantities of water into the air during photosynthesis, which influences precipitation patterns. And the overall forest biomass is crucial to the capture and retention of water, particularly in headwater regions such as Montana’s mountain ranges. In addition, evergreen forests absorb most of the incoming short waves of solar energy, reflecting less energy into the atmosphere to contribute to the greenhouse effect. Woody biomass can also be converted to useable, comparatively clean energy forms.
In short, forests and forestry management has emerged as a key strategy to mitigate the global effect of greenhouse gases.
Alongside industrial contributions, the degradation of the world's forests is a major factor to rising atmospheric levels of carbon dioxide. In the U.S., forest clearing in the 19th and early 20th Centuries probably contributed significant quantities of atmospheric CO2. As the eastern hardwood forests recovered and land-use practices changed, however, U.S. forests again became a sink for carbon by the second half of the 20th century. But the rate of carbon absorption by terrestrial systems in the United States is thought to have peaked around 1960 and has been falling since.