The following main sources of information were used:
1. Global Forest Resources Assessment 2005 (FAO 2006a)
The Global Forest Resources Assessment 2005, FRA 2005, provides a global baseline for trends related to forest resources, their management and uses. For this paper the global level estimates on forest area changes were used, as well as the overall extent of land.
2. The Dynamics of Global Urban Expansion (Angel et al. 2005)
This World Bank study examines the dynamics of urban areas globally and provides estimates on the area changes.
3. FAOSTAT (FAO 2006b)
FAOSTAT is a statistical database that provides access to over 3 million time-series and cross sectional data relating to food and agriculture. FAOSTAT contains data for 200 countries and more than 200 primary products and inputs, including land use trends in agriculture.
Selecting the appropriate land use categories had to made both with respect to the data availability and to the prevailing nomenclature used in environmental studies such as GEO. Inevitably, some compromises and simplifications were necessary. Table 1 views the selected categories and how they relate to similar concepts.
Table 1. Land use categories selected for the study
|
Category |
Comment |
Forest |
Follows the definition used by FRA 2005 (FAO 2006a). Includes all types of forests, but not tree formations under non-forest land use, such as agroforestry systems, urban parks, etc. Data can be drawn directly from FRA 2005. |
Woodland/Grassland |
Woodland and grasslands refer to land that have a vegetation cover other than forests, but that are generally not under intensive land use. The most common land use in this category would be different forms of pasture. FAOSTAT was used to obtain statistics for this category, under the assumption that the FAOSTAT category “Permanent pasture” is equivalent. |
Agricultural crops |
Refers to all areas where temporary or permanent agricultural crops are grown. FAOSTAT was used to obtain statistics, using the category “Arable and permanent crops”. |
Urban area |
Should generally refer to all types of built-up areas including infrastructure. However, the data source (Angel et al. 2005) refers only to cities as such, and focuses on cities with more than 100,000 inhabitants. |
Other land / water |
Includes everything not covered by the above categories, e.g. deserts, polar areas, unvegetated and unihabited land, wetlands that do not fall under above categories and inland water. No authoritative global data source for area trends was found for the components of this category. |
The objective was to fill a matrix showing transitions between the above defined categories at the global level, including also the area remaining within each category.
Year 2000 was selected as a reference year, i.e. the results should illustrate the total extent at year 2000 and changes that occurred during year 2000.
As a first step, the overall extent at year 2000 was estimates based on the available data sources. “Other land” was estimated as the balance between the other categories and the total area.
Secondly, the changes for year 2000 where estimated, category by category, using the available data sources and applying assumptions where data were missing.
