FAO has developed and implemented global terms and definitions of various forest parameters since its first worldwide assessment in 1947. Information presented in FRA Working Paper 1 (FAO 1998) for the current global assessment, FRA 2000, reports on this subject. This paper takes into consideration over 50 years of cumulative experience in FAO working in the field of global forest resources assessments.
The terms and definitions applied in FRA 2000 are artificial constructs which help us to understand and describe the world’s forest vegetation, and how it is changing through time. By necessity, the global definitions are compromises, and their application is subject to interpretation. The sheer magnitude and variability of the forest resources information produced by countries, make this so. Moreover, the wide range of forest formations, ecological conditions and forest cover types, which exist on a global scale, make global definitions necessarily broad.
One of the major analytical tasks in a global assessment is to group and classify detailed information from national classifications according to global definitions. For this exercise, there are many cases where assumptions or approximations must be made. For example, in FRA 2000, more than 650 definitions of forest were assembled from 132 developing countries (from 110 independent surveys). Reducing this information into a highly compressed and discrete set of global classes was a major challenge. At the same time, the original classifications are kept in the Forestry Information System (FORIS) making it possible to make alternative interpretations of national data, should this be needed.
To develop a standard definition of forests, FAO adapted the threshold of a 10% crown cover to describe the minimum canopy density where naturally occurring formations of trees exist as communities. This is opposed to areas where trees exist scattered in the landscape or in rows. The 10% threshold was first used in FAO’s 1963 global assessment and later recommended in 1973 in UNESCO’s landmark study on worldwide vegetation classifications, in which the scientific basis for the limit was established.
The FAO global classification scheme is understandably a subject of debate within the scientific community. However, FAO recognizes that it is not appropriate for all purposes – no classification scheme is. One of the frequently disputed aspects is the use of the threshold of a 10% canopy cover. Some feel that this is too generous a definition for forests. However, these arguments frequently overlook the fact that the definition also excludes areas where other land uses dominate, such as agricultural or urban areas. Another contention is that the global definitions are difficult to apply uniformly at the global level. This is a valid claim, but would hold true for any global classification scheme.
It is recognized that the classification of particular vegetation types according to global classes is difficult. Dry tropical formations present a particular challenge. These areas often contain large expanses of land where tree vegetation is sparse and mixed with woody shrubs. Applying the 10% threshold in such areas is particularly difficult as no distinct boundaries exist between areas of varying canopy cover.
The Kyoto Protocol raises the issue of forest and forest change definitions. KP identifies three change parameters (deforestation, afforestation and reforestation) as a basis for carbon monitoring. The idea is that these area change parameters will give an indication on how the forest carbon storage changes. The current understanding of these definitions definitions, as reflected in the Special Report on Land Use, Land-use Change and Forestry (IPCC 2000) is not far from FAO's definitions. Given the importance of the atmospheric carbon issue, and how forests interact with the atmosphere, FAO is presently reviewing its definitions, and improving its terminology with the intent of making it applicable for carbon studies. At the same time, it should be noted that the FAO definitions must also take other land use perspectives into consideration.
FAO works with its partners, its member countries as well as the scientific community to improve its definitions for global assessments on forest and forest change. Providing leadership in the development of standards through a participatory and scientific process is an important part of the organization’s work. FAO will continue to provide a stable and objective framework for reporting on forests at the global level, while striving to incorporate the needs of other programmes. In this respect, the following information should be viewed as an update of the FRA Working Paper No. 1 and a proposal for extending the FAO definitions to make them more appropriate, and easily understood.