Predicting Global Forest Reforestation Potential

Forests are important determinants of global climate conditions, and they provide countless ecosystem services to support billions of people worldwide. Global-scale forest restoration is one of our most effective weapons in the fight against biodiversity, rural poverty and climate change. In this report, we generate a spatial map of tree density within the potential forest restoration areas delineated by the IUCN/WRI Atlas of Forest Landscape Restoration Opportunities to estimate the potential number of trees that could be restored within global restoration areas. We also estimate the number of trees that might be saved by avoiding deforestation in currently forested areas. We show that the restoration areas have the capacity to support a total of 1.33 trillion trees. However, given that a considerable proportion of these areas already contain forests, we estimate that 589 billion new trees (larger than 10 cm diameter) could be restored within these areas, which would have the potential to store 65-91 Gigatonnes of carbon after forest maturation. These values will increase marginally as deforestation is responsible for the removal of living trees within the restoration areas. However, if only 50% or 25% of the mosaic areas (the largest of the designated restoration types) are available for reforestation, this total number will fall to approximately 360, or 246 billion trees, respectively, with corresponding decreases in potential carbon storage. Given that anthropogenic carbon emissions are currently in the order of ~9-12 Gigatonnes per year, effective global-scale restoration might potentially have a valuable global impact.