In silviculture the activity is known as reforestation, or afforestation, depending on whether the area being planted has or has not recently been forested. Tree planting is grounded in forest science, and if performed properly can result in the successful regeneration of a deforested area. Reforestation is the commercial logging industry's answer to the large-scale destruction of old growth forests, but a planted forest rarely replicates the biodiversity and complexity of a natural forest.[citation needed]
Because trees remove carbon dioxide from the air as they grow, tree planting can be used as a geoengineering technique to remove CO2 from the atmosphere.
Role in climate change
The development of markets for tradeable pollution permits in recent years have opened up a new source of funding for tree planting projects: carbon offsets. The creation of carbon offsets from tree planting projects hinges on the notion that trees help to mitigate climate change by sequestering carbon dioxide as they grow. However, the science linking trees and climate change is largely unsettled, and trees remain a controversial source of offsets.
Climate impacts
Climate scientists believe that human-induced global deforestation is responsible for 18-25% of global climate change. The United Nations, World Bank and other leading nongovernmental organizations are encouraging reforestation, avoided deforestation and other projects that encourage tree planting to mitigate the effects of climate change.
Trees sequester carbon through photosynthesis, converting carbon dioxide and water into molecular dioxygen (O2) and plant organic matter, such as carbohydrates (e.g., cellulose). Hence, forests that grow in area or density and thus increase in organic biomass will reduce atmospheric CO2 levels. (Carbon is released as CO2 if a tree or