Criterion 5: Maintenance of forest contribution to global carbon cycles

Forests are an important component in the global carbon cycle and provide both a source and sink for this basic element on which all life depends. Carbon dioxide (CO₂) is the most prevalent greenhouse gas in the world today and is the leading contributor to the increasing problem of global warming. Forests are a source of carbon by releasing this gas into the atmosphere during decomposition and wild fires. They also act as an important sink by locking up carbon into biomass through photosynthesis, and later contributing it to soils as organic matter. Approximately a seventh of total atmospheric carbon dioxide is passed into vegetation annually.

Although the carbon cycle is a natural phenomenon, humans can dramatically affect its balance by altering the natural forest processes that regulate carbon storage and emission. For example, the way in which timber is processed and used plays an important role. By burning wood for residential and commercial use, carbon emission rates are increased, particularly if forests are not replaced. Alternatively, if forests are properly managed, and if the timber is used for long-term products, such as buildings, forest harvesting could result in a net reduction of atmospheric carbon. Natural disturbances such as insects, diseases, storms and wildfires can also cause large shifts in the global carbon cycle and must be taken into account. The carbon cycle is complex and very difficult to monitor; a better understanding is necessary to manage forests in a way that supports reducing the increase of CO₂ levels in the atmosphere.

Criterion 4	Criterion 6