Tree planting is both a promising and controversial solution to climate change and biodiversity loss. However, this controversy is largely theoretical because we lack detailed information of how tree planting is proceeding on the ground. Here, we compiled a pantropical dataset of 174 tree-planting organizations to determine the type of organizations involved in tree planting, their geographic locations, and tree planting approaches. We found that the number of organizations has increased by 288% in the past 30 years, especially for-profit organizations. These organizations reported planting nearly 1.4 billion trees across 74 countries since 1961. Most frequently organizations reported establishing agroforestry systems or mixed species and single-species plantations or using assisted natural regeneration, suggesting that tree planting programs are designed to support local communities as well as environmental objectives. Moreover, the most frequently reported species were commercial or utilitarian, with the top five including cacao, teak, moringa, mango, and coffee. Finally, despite widespread efforts to plant more trees, there was a pronounced lack of monitoring on websites and in reports; only 18% of organizations mention monitoring at all, and only 5% mention measuring the survival rate of plantings. Greater transparency and greater communication are needed between planting organizations and researchers to apply the most effective ways to restore forest cover. Further, while organizations often aimed to counter environmental problems, the use of the same sets of commercially useful species to meet economic development goals across the globe indicates a need for greater coordination among organizations to avoid biotic homogenization.
