Tropical forests exert a more profound influence on weather patterns, freshwater, natural disasters, biodiversity, food, and human health – both in the countries where forests are found and in distant countries – than any other terrestrial biome. This report explains the variety of environmental services tropical forests provide and the science underlying how forests provide these services. Tropical deforestation and degradation have reduced the area covered by tropical forests from 12 percent to less than 5 percent of Earth’s land area. Forest loss and degradation has reduced or halted the flows of a wide range of ecosystem goods and services, increasing the vulnerability of potentially billions of people to a variety of damaging impacts. Established and emerging science findings suggest that we have substantially underestimated the global importance of tropical forests and the impacts of their loss on human well-being.