What is forest degradation?

Forest degradation is the reduction of the capacity of a forest to provide goods and socio-cultural and environmental services. It involves a change process that negatively affects the characteristics of a forest (e.g. growing stock and biomass, carbon stock, biodiversity, soils, and aesthetic values), resulting in a decline in the provision of goods and services. This change process is caused by disturbances (although not all disturbances cause degradation), which can vary in extent, severity, quality, origin and frequency. Disturbances may be natural (e.g. fire, storms, drought, pests and diseases), or human-induced (e.g. unsustainable logging, invasive non-native – “alien” – species, road construction, mining, shifting cultivation, hunting and grazing), or a combination of both natural and human-induced. Human-induced disturbance may be intentional, such as that caused by logging or grazing, or it may be unintentional, such as that caused by the spread of an invasive alien species. There are also indirect or underlying reasons for forest degradation, such as poverty, inappropriate policies, and unclear tenure rights.

Forest systems always have an inherent range of natural variation and succession stages, and natural or human-induced disturbances do not necessarily lead to degradation. Degradation occurs when the production of an identified forest good or service is consistently below an expected value and is outside the range of variation that would be expected naturally.

Although it is complex to define and measure, forest degradation is a serious problem. It has adverse impacts on forest ecosystems and the goods and services that forests provide; for example, it is considered a significant source of land-related greenhouse gas (GHG) emissions. It is estimated that, in 2010, 27 percent of forest landscapes worldwide (about 1.5 billion hectares) were degraded.   

There is often confusion between the concepts of deforestation and forest degradation. Deforestation is the long-term loss of forest, with no guarantee that the forest will re-establish through natural regeneration or silvicultural measures; it results in a decrease in forest area. Forest degradation does not involve a reduction in forest area but, rather, a qualitative decrease in forest condition. Forest degradation often leads to full-scale deforestation, however, because degraded forests are more easily converted to agricultural lands. Figure 1 depicts the forest degradation continuum, and deforestation.