The quantification of Articles 3.3 and 3.4 activities for accounting purposes will likely be undertaken by country institutions. There may be vast differences in carbon sequestration potential, however, within a Party's territory depending on prevailing socioeconomic conditions, legal-institutional structure, and bio-geophysical conditions. Identification and delineation of these variations will simplify national level reporting and reduce measurement sample requirements (Section 2.4). Such a classification system may also serve as a geographic base for land-based accounting (Section 220.127.116.11).
The socioeconomic conditions of rural areas are normally expressed in statistical data for each administrative unit (e.g., districts or provinces). Legal-administrative characteristics (e.g., land ownership type, national parks, indigenous reserves) are generally defined within historically defined geographical units. Bio-geophysical conditions within a country can be homogeneous or very diverse, depending on the country's size and variation in climatic zones.
The sequestration potential and the percentage of each biophysical zone within a country are important variables. One approach is to apply biome or eco-region concepts, with geographic domains (e.g., polar, humid temperate, dry, humid tropical), divisions (e.g., tundra, boreal forests, prairies, steppe, deserts, savannas, and rainforests), and subdivisions based on elevation. Bailey (1998) and Udvardy (1975) provide world maps that are based on these units; they are also defined in the "life-zones" scheme of Holdridge (1947), which is used in many Latin American countries for national zonations.
For Article 3.4 activities that involve agricultural soils, the agro-ecological zone (AEZ) concept developed by FAO (1996) may be used for within-country geographic subdivisions. This concept combines agroclimatic characteristics with elevation/ topography and soil conditions. Agroclimatic criteria include major climates (boreal, arid, seasonally dry subtropics, humid tropics, etc.), annual growing periods, a dryness index, and the frost period. Initially applied only to developing countries, the AEZ program has been recently extended to all Annex I countries and made available in digital form, accompanied by a digital elevation model and a soil database that includes soil carbon (FAO/IIASA, 1999; Fischer et al., 1999). The combination of the three data sets provides the spatially explicit AEZs. In a simplified form these zones can be used to construct tables of carbon sequestration potential per country (see Chapter 4).
A global database on forest cover and changes in forest cover since 1980 is available through FAO's decadal Forest Assessments, the latest being FRA 2000 (FAO, 1993a; FAO, 1997b; UN-ECE/FAO, 2000). FAO also maintains a global and country-level database on agricultural land use and commodity movements. The FAO/Unesco world soils information (FAO, 1971-1981), although somewhat out of date, is based on correlation of national soil mapping information. Upgrades of the soil database per continent currently underway (SOTER program) (FAO, 1993b; Baumgardner, 1999) will provide spatial terrain data with associated soil profile measurements, climatic conditions, and vegetation or land-use information in relational digital form, based on country-wide geographic information at a medium intensity (scale 1:1 million). The Latin American-Caribbean component was completed in 1998 (FAO/UNEP/ISRIC, 1999); the other continents will be covered in the coming 3 to 6 years, with Africa as a priority region. Technical soil data are provided in terms of the World Reference Base for Soil Classification (WRB, 1998) and Soil Taxonomy (SSS, 1999), where appropriate. These databases can be used to compile country-wide maps on actual and potential soil carbon stock. For some regions, such as North America (Lacelle et al., 1997), generalized soil carbon maps are already available.
In general, national and international geo-referenced databases on the 1990 state of forests and qualitative vegetative cover, soil and terrain conditions, actual land uses, and degree of soil degradation and improvement are approximate only.
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