Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. About half of the world original forests had disappeared by 2011, the majority during the last 50 years. Since 1990 half of the rain forests have disappeared. Forests are removed and converted into other forms such as when it is used as fuel which will emit carbon dioxide. A new study with NASA participation has sharply reduced previous estimates of how much carbon was emitted into Earth’s atmosphere from tropical deforestation in the early 2000s. Research scientist Sassan Saatchi of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., participated in the study, published June 21 in the journal Science. They combined satellite data on gross forest loss and forest carbon stocks to track emissions from deforestation in the world’s tropical forests. The resulting gross emissions estimate of 0.81 billion metric tons of carbon emitted per year is approximately one third of previously published estimates, and represents just 10 percent of the total global human-produced carbon emissions over the time period analyzed (2000 to 2005)