is another common planting method in the United States. Equipment and transportation costs are such that machine planting is generally used for larger acreages where reduced labor cost and high planting productivity are desired. Machine planting is generally restricted to reasonably level terrain with good soil and limited obstacles. While machine planting is most often associated with plantation silviculture in the Southeast and Upper Midwest, it has been used in ecological restoration. Machine planting was used for forest restoration on Alaska's Kenai Peninsula following a large scale Spruce Bark Beetle outbreak in the 1990s. Common tree planting machines include the C&G Tree Planter, Hoedag Tree Planter, Taylor Tree Planter, Reynolds Tree Planter, and Whitfield Tree Planter. Trees for the Future and Plant With Purpose are non-profit organizations based in the U.S. that plant trees in developing countries to improve land management. Other organizations that plant trees in the United States include: American Forests Planting Shade Student run non-profit based in Virginia Beach. Gives citizens the resources to plant trees in their own backyard and other residential areas. Arbor Day Foundation Nature Conservancy Plant-it 2020 USDA Forest Service "Plant-A-Tree" program in which a person can donate to plant trees in the National Forests. Our City Forest TreeFolks empowers central Texans to build stronger communities through planting and caring for trees. Since 1989, TreeFolks has planted over 1.5 million trees in parks, neighborhoods, and natural areas throughout central Texas. 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 working for the IPCC believe 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 tree planting to mitigate the effects of climate change. Trees sequester carbon through photosynthesis, converting carbon dioxide and water molecules 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 levels. (Carbon is released as if