It is possible for forest lands to become degraded without being completely deforested (converted into a non-forest land type, such as animal pasture or palm oil plantation). A degraded forest is an area of forested land that has been damaged by human activity, forest fires, pests, disease, or climate change. Relative to a healthy forest, tree cover is greatly reduced, and the capability of the degraded forest to provide ecosystem services is impaired. (Ecosystem services provided by forests include wood, filtration of air pollutants, soil and erosion protection, nutrient cycling, habitat for fish and wildlife, water filtration, recreation, and more.) Degraded forests contain less stored carbon per acre and sequester less carbon per year per acre than healthy, growing forests.

Forest restoration activities include measures to accelerate the recovery of the degraded land (such as tree planting and building erosion control structures) as well as steps to protect the land from activities that perpetuate degradation, such as animal grazing. Measures that improve crop yields on existing farmland can reduce the economic appetite for new cropland, giving degraded forests time to recover (and protecting healthy forests from degradation and deforestation).