Forest change processes are central to several national and international forest policy agendas. They are also of high interest to the public in general and are often referred to by media. Many organisations are engaged in forest change issues, and the definitions are therefore important and also politically sensitive. The below summarizes the definitions as used by FAO's Forestry Department. The definitions have not changed since the previous publication (FRA 1998), but the explanations have been rewritten to be clearer and also better support the discussions on climate change issues. Five terms are defined in this section. Figure 1. gives an overview of how these relate.
Note that to determine whether the removal of trees from an area is a deforestation it is necessary to predict the future development for the area. If new forest trees are established in the relatively near future, the land is classified as forest throughout the regeneration period (and this regrowth is named "reforestation"). If, on the other hand, a sufficient density of trees is not established in the relatively near future, or if land is converted to other land use, the area should be considered deforested.
Note also that the time frame is central to the forest change definitions and that the length of the threshold period, defaulted to ten years, should be used consistently when applying the terms, to avoid overlaps or gaps in the reporting. Thus "long-term" refers to ten years or more, and "temporary" refers to shorter than ten years. Note that local climatological conditions, land use contexts or the purpose of the analysis may justify that a longer threshold period is used.
Figure 1. Relationships between forest change terms. Forest degradation and Forest improvement occur within forests that continuously stay above the 10% canopy threshold. Reforestation occurs when forests regrow after temporarily having had below 10% canopy cover, but were considered as forests throughout that time. Deforestation and Afforestation represent the transfers between forest and other land use classes.
Deforestation is the conversion of forest to another land use or the long-term reduction of tree canopy cover below the 10% threshold.
Deforestation implies the long-term or permanent loss of forest cover. Such a loss can only be caused and maintained through a continued man-induced or natural perturbation. Deforestation includes, for example, areas of forest converted to agriculture (including agroforestry), pasture, water reservoirs and urban areas. The term specifically excludes areas where the trees have been removed, due, for example, to harvesting or logging, and where the forest is expected to regenerate naturally or with the aid of silvicultural measures within the long-term. Unless followed by clearing of the remaining logged-over forest for the introduction of alternative land-uses, and the maintenance of the clearings through continued disturbance, forests commonly regenerate, although often to a different, secondary condition. In areas of shifting agriculture, forest, forest fallow and agricultural lands appear in a dynamic pattern where deforestation and the return of forest occur frequently in small patches. To simplify reporting of such areas, the net change over a larger area is typically used. Deforestation also includes areas where overutilization or changing environmental conditions, influence the forest to an extent that it cannot (currently) sustain a tree cover above the 10% threshold, for example burnt-over areas where severe ground conditions or recurring fires for the long-term prevents the return of forest formations, or areas that after clearcutting cannot regenerate because of frost, competing vegetation, or other natural conditions. The concept “long-term” is central in this definition and is defined as ten years. Local climatological conditions, land use contexts or the purpose of the analysis may however justify that a longer time frame is used.
Afforestation is the conversion from other land uses into forest, or the increase of the canopy cover to above the 10% threshold.
Afforestation is the reverse of deforestation and includes areas that are actively converted from other land uses into forest through silvicultural measures. Afforestation also includes natural transitions into forest, for example on abandoned agricultural land or in burnt-over areas that have not been classified as forest during the barren period. As for deforestation, the conversion should be long-term, that is areas where the transition into forest is expected to last less than ten years, for example due to recurring fires, should not be classified as afforestation areas. The concept “long-term” is central in this definition and is defined as ten years. Local climatological conditions, land use contexts or the purpose of the analysis may however justify that a longer time frame is used.
Reforestation is the re-establishment of forest formations after a temporary condition with less than 10% canopy cover due to human-induced or natural perturbations.
The definition of forest clearly states that forests under regeneration are considered as forests even if the canopy cover is temporarily below 10 per cent. Many forest management regimes include clearcutting followed by regeneration, and several natural processes, notably forest fires and windfalls, may lead to a temporary situation with less than 10 percent canopy cover. In these cases, the area is considered as forest, provided that the re-establishment (i.e. reforestation) to above 10 percent canopy cover takes place within the relatively near future. As for deforestation, the time frame is central. The concept "temporary" is central in this definition and is defined as less than ten years. Local climatological or land use contexts, or the purpose of the analysis, may however justify that a longer time frame is used.
Forest degradation is a reduction of the canopy cover or stocking within a forest.
For the purpose of having a harmonized set of forest and forest change definitions, that also is measurable with conventional techniques, forest degradation is assumed to be indicated by the reduction of canopy cover and/or stocking of the forest through logging, fire, windfelling or other events, provided that the canopy cover stays above 10% (cf. definition of forest). In a more general sense, forest degradation is the long-term reduction of the overall potential supply of benefits from the forest, which includes wood, biodiversity and any other product or service.
Forest improvement is the increase of the canopy cover or stocking within a forest.
For the purpose of having a harmonized set of forest and forest change definitions, that also is measurable with conventional techniques, forest improvement is assumed to be indicated by the increase of canopy cover and/or stocking of the forest through growth. In a more general sense (cf. forest degradation) forest improvement is the long-term increase of the overall potential supply of benefits from the forest, which includes wood, biodiversity and any other product or service.