The World Wildlife Fund lists reduced biodiversity, increased greenhouse gas emissions, disruptions in the water cycle and increased erosion as the primary effects of deforestation. Millions of people directly rely on forests for subsistence and the loss of forests poses a risk to their lifestyles. Deforestation occurs when tracts of forest are logged and burned for timber or to alter the land for agricultural or infrastructure purposes.
According to the World Wildlife Fund, nearly 80 percent of the world's species are found in rain forests. Removal of trees results in lost habitat, putting thousands of species at risk of extinction. Forests act as carbon sinks and store hundreds of gigatons of carbon, preventing it from entering the atmosphere. The loss and burning of these forests results in greater greenhouse gas concentrations around the globe. Trees are a critical component of local water cycles and remove water from the ground, which later evaporates into the air. Trees also filter water down to the ground, and leaf litter acts as ground cover, keeping soil in place. Tracts of lands that are bare after deforestation tend to be very dry, lacking topsoil, and are susceptible to runoff events.
The World Wildlife Fund reports that 12 to 15 million hectares of land are deforested each year. Rain forests are at the greatest risk of deforestation, and 87 percent of all deforestation occurs in just 10 tropical nations.