Land Resources

AEZ - Agro-ecological Zoning System (Release 2002)

What is AEZ
The main system for land resource assessment is FAO’s agro-ecological zoning (AEZ) methodology and supporting software packages for application at global, regional, national and sub-national levels. AEZ uses various databases, models and decision support tools.

When to use AEZ
Useful as a tool of assessment of land resources for better planning and management and monitoring of these resources. AEZ can be used in various assessment applications, including:

- land resource inventory;
- inventory of land utilization types and production systems, including indigenous systems, and their requirements;
- potential yield calculation;
- land suitability and land productivity evaluation , including forestry and livestock productivity;
- estimation of arable areas mapping agro-climatic zones, problem soil areas, agro-ecological zones, land suitability, quantitative estimates on potential crop areas, yields and production;
- land degradation assessment, population supporting capacity assessment and - land use optimization modelling;
- assessing and mapping flood and drought damages to crops;
- assessment of impact of climate change; monitoring land resources development

The agro-ecological zones methodology has been in use since 1978 for determining agricultural production potentials and carrying capacity of the world’s land area. An agro-ecological zone, as originally defined, is comprised of all parts of gridcells on a georeferenced map that have uniform soil and climate characteristics.

The suitability of each of these zones for rainfed production of various crops, under different input and management scenarios is then evaluated. The yield potential of the crops most suited to each zone where rainfed crop production is possible, determines the overall agricultural production potential of that zone. Crops evaluated originally include food, fibre and fodder crops and pasture grasses.

The Food and Agriculture Organization of the United Nations (FAO), in collaboration with the International Institute for Applied Systems Analysis (IIASA), has updated its agro-ecological zones (AEZ) methodology (FAO & IIASA, 2002). The updated version permits a more refined evaluation of biophysical limitations than the original, and takes into account the production potential of a larger number of crops.

In conjunction with the updating exercise, a worldwide spatial land resources database has been created that contains both primary datasets and derived datasets for a large number of variables that affect the production potential of the world’s land area or reflect the choices that people have made about how to use the land.

The AEZ framework incorporates the following basic elements:

- a georeferenced land resources database that contains some 2.2 million gridcells, and includes (i) an environmental conditions component comprised of georeferenced global databases for climate, soils, terrain and elevation, and (ii) a spatial land use and land cover component covering forests, protected areas, irrigated areas, population distribution and density, land required for habitation and infrastructure, estimates of cropland, grazing land and sparsely vegetated or barren land, and farming systems;
-  a standardized framework for the characterization of soil, terrain and climatic conditions relevant to agricultural production, and identification of areas with specific climate, soil and terrain constraints to rainfed crop production;
- selected agricultural production systems with defined input and management relationships, and cropspecific environmental requirements and adaptability characteristics; these are termed land utilization types (LUTs);

-  procedures for calculating the potential agronomically attainable yield and for matching environmental requirements of individual crops and LUTs with the respective environmental characteristics contained in the land resources database, by land unit and gridcell, thus permitting estimation of crop-specific suitability indices for each gridcell in the database, under different levels of inputs and management conditions;

- quantification of crop and land productivity potential under different cropping pattern and LUT assumptions;

-  applications for estimating the land’s population-supporting capacity and for multiple-criteria optimization of land resource use for sustainable agricultural development, incorporating socioeconomic and demographic as well as environmental factors.

The AEZ starts with climate and uses terrain and soil types as modifiers, that is climate is determining; only if climate is suitable will the suitability of the terrain and the soil type be considered. A complete description of the methodology and results obtained for regions across the globe can be found in FAO & IIASA, 2002 and 2003.